A modular input and output system

Abstract

A low power scalable plug and play modular input / output system 100 is configured to provide communication and power delivery between a plurality of connected modules 150 of the system. The system comprises a primary gateway module 7 having at least one module communication channel 10 comprising a 2-wire interface and at least one secondary module comprising an input / output, I / O, module 7 having at least one module communication channel comprising a 2-wire interface 10 for coupling said secondary module 1 to the primary gateway module 7. Each 2-wire interface is configured to provide power delivery and data communication between connected modules together on a 2-wire bus. The system 100 is configured to deliver power and data between modules 150 based on a time division protocol, power and data being delivered separately in short time segments, and the duration of the segments being controllable according to the power demands of the modules. Modules including a sensor hub module, an output module and a hybrid input and output module are also provided.

Description

Field The present description relates to test and measurement systems. In particular, it relates to providing a modular system having a gateway and input and output modules, including for example a modular test and measurement system. Background In one previous approach standalone instruments which carry out a specific task, e.g. thermometer or multimeter have been used for test and measurement. Such instruments often require a computer for operation and are used as a standalone unit. Generally, they cannot be integrated into a bigger system. In another approach a rack type system is used where a number of instruments plug into a chassis which has a fixed number of slots to accommodate said instruments may be provided. The standalone instruments are convenient to use and require very little user configuration. However, they tend to be bulky and because they come in all shapes and sizes are not easily combined into a single measurement system. Special adaptors are required to facilitate placement within a rack system, which is in itself large and bulky. When such instruments are in a rack system, this results in bulky wiring harnesses from all the various sensors and actuators converging to a single location. The entire system becomes extremely difficult to move from one location to another with potential damage to the sensor wiring. EP3021116B1 for example shows a chassis system arrangement comprising a number of slots which accommodate various sensor modules. The modules do not function on their own and require insertion into the chassis to enable operation. While not as big as a rack system, a chassis system is also bulky and difficult to move and is generally constrained to bench locations. In addition, such chassis-based systems, often require significant user input to setup and program the desired measurement functionality. They also require considerable resources as the chassis system needs a metal frame, multiple circuit boards to support the backplane connectors, module communications and chassis power requirements. Therefore, there exists a need for an improved test and measurement system. Summary According to a first aspect there is provided a low power scalable plug and play modular input / output, I / O, system (100) configured to provide communication and power delivery between a plurality of connected modules (150) of the system, the system comprising: - a primary gateway module (7) having at least one module communication channel (190) comprising a 2-wire interface (2); - at least one secondary module comprising an input / output, I / O, module (7, 9, 11) having at least one module communication channel (180) comprising a 2-wire interface (2) for coupling said secondary module to the primary gateway module (7), each 2-wire interface being configured to provide power delivery and data communication between connected modules together on a 2-wire bus; and wherein the system (100) is configured to deliver power and data between modules (150) based on a time division protocol, power and data being delivered separately in short time segments, and the duration of the segments being controllable according to the power demands of the modules (150). The modular I / O system is configured to allow flexibility in the location of secondary modules. For example, one or more secondary modules may be located remotely from the gateway and any external computing device, e.g. near to the test location. Data obtained from inputs is processed and stored at the remote module local to the sensor(s) for communication to the external gateway module. Data to and from one or more connected secondary modules may be communicated via a unitary or consolidated communication channel, and via a unique coupling to the external gateway module. The same coupling provides a communication coupling between the sensor hub and external gateway module, and an electrical coupling to provide power to the sensor hub. That way multiple wire connections from input sensors or output loads do not need to route to a single location - but rather can be concentrated locally the near the inputs and outputs. The inputs and outputs are connected via shorter connections to a local secondary module and communication from the module to a gateway is provided via a 2-wire connection. This also means the computer controlling the system can be located distant from the input or output. Further, the system is configured to operate at low voltage and low power thereby making it cost effective to implement and applicable to battery powered applications. The system of the claims provides an improved arrangement as and an alternative to having multiple connections between individual inputs and outputs and an external gateway module. The system is also configured, being a modular system, to allow for expansion if further capacity is needed. In one embodiment of the first aspect, the secondary I / O module comprises a sensor hub module (7) comprising: a sensor hub module controller (33) configured to receive sensor signals from one or more sensors coupled to the sensor hub module (1), and to communicate the sensor signals to the gateway module (7). In one embodiment of the first aspect, the secondary I / O module comprises: (i) an output module (11) comprising one or more outputs for driving loads, the output module configured to provide output control signals from the gateway module (7) to connected devices or loads; or (ii) an input and output module (9) having one or more input and output ports, the input ports being configured for connection to sensors to receive sensor input, and the outputs being configured for driving loads. It will be appreciated that the output control signals provided by the output module maybe digital control signals, or analog control signals. Further the output control signals may comprise digital and analog control signals. The secondary modules have similar functional blocks for control of input and / or outputs and for control of communication via the module communication protocol. The modules may be configured to comprise one or more output channels and one or more input channels. It will be appreciated that the modules of the system may be configured to comprise various combination of input and output channels. For example, a gateway module may further comprise one or more input channels for receiving a sensor input. A gateway module may further comprise one or more output channels for connecting to a load. Taking account of the advantages of the communication and power delivery in the modular system - the system supports flexibility in the arrangement of the input and output functions of the modules. In one embodiment of the first aspect, the gateway module further comprises a gateway controller (51) configured to control the communication and power delivery between the gateway module and connected secondary modules, and further configured to control communication between the gateway module (7) and an external computing device or network. The gateway defines a primary module of the system configured as a gateway between an external network or processor or computing device and the modular system and between one or more connected secondary modules. In one embodiment of the first aspect, the gateway module (7) further comprises: a communication circuit block comprising one or more module communication channels (190) and one or more communication interfaces (2) for coupling to modules (150) of the system (100), a transmitter and receiver, and a power delivery circuit, the communications between modules coupled to the gateway being managed by gateway controller (51). The arrangements of the specification advantageously allow for a local connection and local communication between sensors located in proximity to a sensor hub. In such a case it is envisaged that multiple wires may be used to connect multiple sensors to the sensor hub. The sensors and sensor hub may be located in test chamber. The data received at the sensor hub is then delivered via the 2-wire interface and a 2-wire cable to an external gateway that can be located remotely and at a distance from the sensors and sensor hub. The gateway may be located externally of the test chamber. The arrangement advantageously avoids the need for multiple cable connections between sensors and a controller. The low power data and power communication protocol based on a time division allows for communication at greater distances -for example up to at least 100 metres. The system is operable at voltages in a range of as low as about 2V to 5V. The 2-wire interface may be operated at a current in a range of about up to 20mA - 100mA and a bandwidth in a range of up to about 20kbps - 100 kbps. In one embodiment of the first aspect, the gateway module further comprises an external communication channel (193) for communication of signal data received from connected modules (150) of the modular system (100) to an external computing device or network and for communication of signals from the external computing device or network to the modular system. Further, the communication interface 2 may be configured to act as a digital input / output or analog input. In another arrangement the gateway 7 may be configured to use the communication interface 2 to switch on / off devices, for example relays, in the event that the communications feature is not required. In one embodiment of the first aspect, the external communication channel (193) comprises an isolated channel configurated to isolate the communication channel from the other components of the gateway. Thus, in the case of a sensor hub module, or output module, or I / O module, or gateway module having isolated sensor channels (181) which in use in a modular system is arranged in combination with a gateway 7 having an isolated external communication channel the overall arrangement effectively and advantageously provides a double isolated protection barrier between the sensor 13 or other input and the external computing device or network 12. In one embodiment of the first aspect, the communication circuit block of the gateway module comprises at least one 2-wire interface, and further comprising one or more 4-wire interfaces. In a further embodiment the gateway module may further comprise one or more interfaces comprising at least 4-wires. The 4-wire interface may be operated at a voltage and current supply in ranges of up to about 8-18V, or about a nominal 12V at 500mA - 1 A, and at data speeds up to 10Mbps. In one embodiment of the first aspect, the power and data are delivered in a non-modulated manner. Advantageously the delivery of data and power does not require a modulated signal or a modulator. This further supports efficiency in use of resources and a reduction in the components required for operation. This method 600 of delivery of power together with data on a multiple-wire comprising a 2-wire bus advantageously eliminates the need for modulation, which has the further advantages of reduction in resource demands and costs. It will be appreciated that modulation is expensive to implement. The arrangement of the communication method is based on a nonmodulated communication protocol. Therefore, for the communication method no additional features or processes are required to provide modulation - as would typically be seen in prior systems. The system may further comprise an additional 4-wire interface arrangement. In one embodiment of the first aspect, the modules of the system are configured for communication and power delivery based on a common module power delivery and communication protocol. The system is configured to operate at low voltage and low power and is advantageously cost effective to implement and suitable for battery powered applications. In one embodiment of the first aspect, the sensor hub module (1) comprises one or more internal sensors (64) mounted onboard the sensor hub. In one embodiment of the first aspect, wherein the sensor hub module which comprises: one or more sensor channels (181) each comprising a sensor connector (3) configured as a sensor input for coupling to an external sensor (13) to receive a sensor signal for delivery to the sensor hub module controller (33) via corresponding sensor channel (181). In one embodiment of the first aspect, each sensor channel (181) comprises a sensor signal circuit (34) and wherein the sensor signal is communicated via the sensor signal circuit (34) to the sensor hub controller (33), and wherein the sensor signal circuit (34) is configured to provide signal conditioning including one or more of filtering, amplification, and analog to digital conversion. In one embodiment of the first aspect, the sensor hub module (1) further comprises: a sensor block (182) comprising sensors or sensor channels, and arrangements for processing received sensor signals; and a communication circuit block (180) comprising the at least one interface connector (2) for communication with other connected modules comprising one or more of a gateway module, a sensor hub module, an output module or an input / output module. In one embodiment of the first aspect, each sensor channel (181) further comprises a channel-to-channel galvanic isolator (35), wherein the galvanic isolator (35) is configured to provide a power and data barrier between the sensor signal circuits (34) of each channel, and between the sensor channels (181) and the communication interface (2). In one embodiment of the first aspect, the module comprises at least one input port or at least one output port or a combination of at least one input and at least one output ports, wherein one or more of said ports comprises at least one galvanic isolator (35, 65) to provide isolation between said port and any of the communications interfaces and between said port and other ports. In one embodiment of the first aspect, the module comprises at least one input port or at least one output port or a combination of at least one input and at least one output ports; wherein all said ports share a galvanic isolator (178) to provide isolation between said ports and any of the communications interfaces. In one embodiment of the first aspect, each input or output channel (181, 202) of a module of the system may further comprise a channel-to-channel galvanic isolator (35, 65), wherein the galvanic isolator (35, 65) is configured to provide a power and data barrier between the input and output channels or the signal circuits of each channel, and between the input and output channels (181,202) and the communication interface (2). The channel-to-channel galvanic isolation blocks (35) also referred to as channel-to-channel isolators (35) provided in the sensor hub advantageously protects the upstream computer hardware from damage and users from electric shock in the event a sensor makes contact with a high voltage. These features are advantageous when sensors are being used in high voltage test environments. The arrangement facilitates a safe operation when the sensors are connected to different voltages. The isolation also breaks the common mode path to ground. The isolation block is configured to isolate both power and data to the sensor interfaces. In effect the arrangement provides increased safety and protection in that only isolated safe low-voltage 2-wire interface cable exits the test environment area to the external gateway. Similarly in the arrangements in which the external gateway comprises one or more sensor test channels, each sensor test channel may further comprise a channel-to-channel galvanic isolator. The isolation may also apply to input channels on a gateway module or other I / O module. The isolation may also apply to output channels in any module. In one embodiment of the first aspect, the system (100) is configured to deliver data and power separately inside short time segments, the data being delivered in a first time segment (71) and power being delivered in second different time segment (72), wherein the duration of the segments being controllable according to the power demands of the modules (150) on the 2-wire interface (2). In a further arrangement, a secondary module may be configured to initiate a communication with a gateway 7 by generating a pulse on the 2-wire interface during a long Power Delivery phase 72. In one embodiment of the first aspect, the gateway module (7) is configured to implement the time division delivery of data and power, wherein the gateway module comprises a transmitter (54) configured to route a waveform having first- and second- time segments generated by the controller circuit (51). In one embodiment of the first aspect, the controller (51) is configured during a first data phase time segment to generate a waveform wherein the width of the pulse determines the value of the data bits. In one embodiment of the first aspect, the system may be configured such that a pulse may represent two binary bits, Further the system is configured such that long message headers may be replaced by a configurable 2-bit code which occupies only one PWM pulse. In another embodiment of the first aspect, the system (100) is configured to carry out a binary search on the unique 32-bit ID (or larger sized ID) which is assigned to each module (1,7, 9, 11) at the time of production. Once the module, with the corresponding ID is found, it is assigned a short address, in the range 2 bits to 8 bits, which is then used, during requests for sensor data, to select a sensor hub module to send its data. The unique 32-bit ID in conjunction with a binary search algorithm advantageously eliminates the need for a manual assignment of addresses to modules 150 before they can communicate on a network or in a modular system 100. In one embodiment of the first aspect, the gateway module (7) further comprises a resistor (61) and capacitor (60) to provide line balancing and filtering to reduce electromagnetic noise. In one embodiment of the first aspect, when power is being delivered, the transmitter (54) is set to logic high output, and a current limit switch (55) is turned on to provide a low impedance to power the modules on the 2-wire network. In one embodiment of the first aspect, the secondary I / O module is configured to separate the received power and data signal into its data and power components, the secondary I / O module further comprising a regulator (32), and a receive buffer (30), wherein the secondary modules of the system may comprise a sensor hub module (1), an output module (11) or an input / output module (9). In one embodiment of the first aspect, the I / O module is configured to transmit data by switching on / off its transmitter (31). In one embodiment of the first aspect, the modules (150) of the system (100) each comprise corresponding mechanical coupling features to allow coupling of a first module to one or more different modules of the system, the mechanical coupling features comprising corresponding receivers and protrusions that allow for location and connection of modules. In one embodiment of the first aspect, the modules (150) of the system are further sized and dimensioned to support mechanical coupling, wherein each module is dimensioned such that a footprint thereof is a multiple of a footprint of a module having base dimensions. In one embodiment of the first aspect, the modules have at least one aperture (6) which provides means of attaching a module to a fixture or securing a stack of modules. In one embodiment of the first aspect, the gateway module (7) is further configured to detect the capacitance of the 2-wire interface between the gateway module and connected I / O modules and to generate a capacitance correction factor to correct for distortion, due to capacitance, in a signal received from the connected I / O module. The capacitance detected include the capacitance between the gateway module and the relevant I / O module - and as such includes capacitance of the 2-wire interfaces and the cable between the gateway module and connected I / O module. In one embodiment of the first aspect, the one or more of the secondary modules comprise: a second module communication interface connector (2) configured for coupling a first secondary module to a second secondary module of the system in a daisy chain configuration; wherein each interface connector (2) comprises a 2-wire interface connector, configured for delivery of power and data based on a time division protocol, wherein data and power are delivered separately in short time segments and wherein the duration of the segments is controllable according to the power demands of any connected secondary modules. The system advantageously further allows for daisy chaining of I / O modules hubs - again supporting a reduction in cabling needed to connect multiple sensor hubs to an external gateway. Further, the system also allows for tailoring of resources in the event that a more limited sensor capacity is needed and allow for saving in resources including physical components, energy, communication resources. For example, a system may include a remote sensor hub, locatable local to the connected sensors and test site, and a single gateway. At the same time, the system can be extended or limited as required and the components are configured to couple directly to facilitate tailoring. In one embodiment of the first aspect, the system may comprise one or more secondary modules including at least one sensor hub module, wherein the sensor hub module is locatable remotely in a test environment such as a test chamber, and configured to receive sensor signals from a plurality of sensors and to communicate said sensor signals back to the gateway module via a common 2-wire connection, together with power delivery and any digital output communication. In one embodiment of the first aspect, the sensor hub module is configured for coupling to a plurality of external sensors at one or more sensor channels to receive sensor signals on a plurality of sensor channels and to deliver the sensor data to the connected gateway together on a common 2-wire connection, together with power delivery and any digital output communication. According to a second aspect there is provided a sensor hub module (1) of a modular input and output system comprising: a first module communication interface connector (2) configured for coupling the sensor hub module (1) to another gateway module of the system; a second module communication interface connector (2) configured for coupling the sensor hub module to a further secondary module of the system in a daisy chain configuration; a sensor hub module controller (33) configured to receive sensor signals from one or more sensors coupled to the sensor hub module (1), and to communicate the sensor signals to the gateway module (7); wherein each interface connector (2) comprises a 2-wire interface connector to provide power and data communication; wherein the system is configured to operate at low power and low voltage, the power and data being delivered together on a 2-wire bus; wherein the system (100) is configured to deliver power and data between modules (150) based on a time division protocol, power and data being delivered separately in short time segments, and the duration of the segments being controllable according to the power demands of the modules (150). According to a third aspect there is provided an output module (11) of a modular input and output system comprising: a first module communication interface connector (2) configured for coupling the output module (11) to a gateway module of the system directly or via a daisy chain connection via other modules of the system; a second module communication interface connector (2) configured for coupling the output module to a further secondary module of the system in a daisy chain configuration; an output module controller (33) configured to communicate the control signals received from the gateway module to a connected load; wherein each interface connector (2) comprises a 2-wire interface connector to provide power and data communication; wherein the system is configured to operate at low power and low voltage, the power and data being delivered together on a 2-wire bus; wherein the system (100) is configured to deliver power and data between modules (150) based on a time division protocol, power and data being delivered separately in short time segments, and the duration of the segments being controllable according to the power demands of the modules (150). According to a fourth aspect there is provided a gateway module (7) of a modular input and output system comprising: one or more module communication interfaces (2), wherein the or each communication interface (2) being a 2- wire interface configured to couple the gateway to a secondary module of the system to provide power and data communication between the gateway and the connected module, wherein power and data are delivered together on a two-wire bus; a controller configured to control power delivery and communication with a connected modules (150) based on a time division protocol; wherein data and power are delivered separately in short time segments and wherein the duration of the segments is controllable according to the power demands of the modules (150) on the multiple-wire interface (2). According to a fourth aspect therein is provided an input / output, I / O module (9) of a modular input and output system comprising: a first module communication interface connector (2) configured for coupling the output module (9) to a gateway module (7) of the system directly or via a daisy chain connection via other modules of the system; a second module communication interface connector (2) configured for coupling the I / O module to a further secondary module of the system in a daisy chain configuration; one or more input channels (13) and one or more output channels (14); an I / O module controller (33) configured to communicate the control signals received from the gateway module to a connected load, or to communication input signal received from a connected input to the gateway module; wherein each interface connector (2) comprises a 2-wire interface connector to provide power and data communication; wherein the system is configured to operate at low power and low voltage, the power and data being delivered together on a 2-wire bus; wherein the system (100) is configured to deliver power and data between modules (150) based on a time division protocol, power and data being delivered separately in short time segments, and the duration of the segments being controllable according to the power demands of the modules (150). The sensor hub module, the output module, the input / output module or the gateway module, may further comprise: a sensor block (182) comprising sensor channels comprising an onboard sensor, and / or at least one sensor interface connector configured for coupling to one or more external sensors, the sensor block coupled with the controller (51,33) of the module which is configured to receive sensor signals and to provide communication of sensor signals; and a communication circuit block (180) comprising the at least one interface connector (2) for communication with other connected modules comprising one or more of a gateway module, a sensor hub module, an output module or an input / output module. According to a fifth aspect there is provided a low power scalable plug and play modular test and measurement system (100) for obtaining sensor measurement data and controlling devices in a test environment, the modular test system (100) including a plurality of modules (150) comprising: - a sensor hub module (1); and - a gateway module (7) comprising a communication interface connector (2); wherein the sensor hub module (1) comprises: a communication interface connector (2) configured for coupling the sensor hub module (1) to the gateway module (7); a sensor hub module controller (33) configured to receive sensor signals from one or more sensors coupled to the sensor hub module (1), and to communicate the sensor signals to the external gateway module (7); wherein each interface connector (2) comprises a 2-wire interface connector to provide power and data communication; wherein the system is configured to operate at low power and low voltage, the power and data being delivered together on a 2-wire bus; wherein the system (100) is configured to deliver power and data between modules (150) based on a time division protocol, power and data being delivered separately in short time segments, and the duration of the segments being controllable according to the power demands of the modules (150). The features of the system of the first aspect as described above may be provided in combination to the arrangements of the sensor hub module, the gateway module, the output module and the I / O module of the second to fourth aspects and to the system of the fifth aspect. According to a sixth aspect there is provided low power scalable plug and play modular input / output, I / O, system (100) configured to provide communication and power delivery between a plurality of connected modules (150) of the system, the system comprising: - a primary gateway module (7) having at least one module communication channel (190) comprising a 2-wire interface (2); - at least one secondary module comprising an input / output, I / O, module (7, 9, 11) having at least one module communication channel (180) comprising a 2-wire interface (2) for coupling said secondary module to the primary gateway module (7), each 2-wire interface being configured to provide power delivery and data communication between connected modules together on a 2-wire bus; and wherein the system (100) is configured to deliver power and data between modules (150) based on a time division protocol, power and data being delivered separately in short time segments, In an embodiment of the sixth aspect, the duration of the segments may be controlled according to the power demands of the modules (150). The further features and embodiments described above with reference to the system of the first aspect, may also be provided in combination with the system of the sixth aspect. Brief Description of the Drawings Embodiments of the present disclosure will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows an exemplary arrangement of a sensor hub module according to an embodiment of the specification with the communication connectors, sensor connectors and mechanical fastening features. In this embodiment there are four sensor inputs configured to connect to sensors for example thermocouples and two 2-pin module connectors which connect to the 2-wire bus carrying power and data. The receivers on the top mate with feet on the bottom of another module, to provide a mechanical fixing. Figure 2 shows an exemplary arrangement of a gateway module according to an embodiment of the specification with a communication connector, sensor connector, USB connector and mechanical fastening features. Here the gateway module has an input sensor connector or interface configured to accommodate a thermocouple mini connector and a single 2-wire communication interface connector. As in the case of the sensor hub module it uses the same mechanical connection scheme. The gateway module shown is half the length ((y direction / longitudinal direction) of the sensor hub modules and hence two gateway modules can fit on top. Both hub and gateway modules are based on an integral scalar of a base dimension. Figure 3 shows a sensor hub module according to Figure 1 clipping into another similar sensor hub module. The sensor hubs (also referred to as sensor hub modules) are pushed together and are kept in place by mechanical friction. Figure 4 shows two sensor hubs according to Figure 1 in the mated position. The sensor hubs are simply pushed together with the feet or protrusions on the top hub engaged with the apertures or receivers on the bottom hub. The hubs are disengaged from each other by pulling them apart. Figure 5 shows a gateway module according to Figure 2 mated with sensor hub module according to Figure 1. This coupling is the same as for a sensor hub module to sensor hub module. Figure 6 shows an exemplary arrangement of a mounting plate according to an embodiment of the present specification, as part of a modular system. The mounting plate facilitates attachment of a module to a wall or base or other support. The mounting plate has through holes to allow it to be fixed to the base using fasteners locatable therein. It also has the same protrusion pattern as the modules to facilitate attachment to hubs and gateway modules. Figure 7 shows a cover according to exemplary arrangement as part of a modular system according to an embodiment of the present specification. The cover is configured to provide a more permanent secure mechanical connection of a series of modules to each other. This could be used in environments where there was high vibration. Figure 8 shows an exemplary arrangement of a gateway and sensor hub modules according to an embodiment of the present specification daisy chained together using 2-wire cables. The gateway on the far left has a 2-wire interface connector which connects via a 2-wire cable 10 to the first sensor hub. This sensor hub has two 2-wire connectors such that it in turn can connect to a second sensor hub, via a second 2-wire cable, creating a daisy chained connection arrangement. Power and data pass from the gateway module to all sensor hubs or connected modules using this arrangement of daisy chained cabling. Even though only two sensor hubs are shown connected to a gateway module, it will be appreciated that more can be connected in the daisy chain fashion. For example, a 2-wire network could consist of one gateway module 7 and 5 sensor hub modules 1. Figure 9 shows an exemplary arrangement of a gateway module and sensor hubs daisy chained together using 2-wire cables where they are also mechanically fitted together in a stacked arrangement according to an embodiment of the present specification. Figure 10 shows an exemplary distributed arrangement of gateway module and sensor hubs daisy chained together using 2-wire cables according to an embodiment of the present specification. In this exemplary arrangement the distance between modules could be up to 100m. This feature is useful when measurements are required from two locations distant from each other. Figure 11 shows a block diagram of an exemplary arrangement of the specification comprising a computer, gateway module, sensor hub modules and an output module. The computer or processor is configured to connect to the gateway using a USB interface in this arrangement. It will be appreciated that alternative arrangements or interfaces would also be suitable. The gateway connects to the sensor hubs and output module with a 2-wire interface wherein they are all daisy chained together. In this arrangement the modular system includes a gateway and two sensor hubs having sensor inputs, and an output module having digital outputs. Figures 12A, 12Beach showa block diagram of an exemplary arrangement of a modular system according to the specification comprising a computer, gateway, sensor hubs and output module. The computer connects to the gateway using a WiFi or Ethernet interface. The gateway connects to the hubs and output module with a 2-wire interface wherein they are all daisy chained together. In this arrangement the gateway and two hubs having sensor inputs, and the output module has digital outputs. Figures 13A, 13C shows an exemplary arrangement of an embodiment of a sensor hub according to the specification illustrating the internal functional blocks. These comprise sensor interface connectors, a signal conditioning circuit for each sensor input, a controller block which performs analog to digital conversion and handles the communications protocol. It may also communicate with thermocouple amplifier circuits to control and read digitized measurements. A regulator provides a stable voltage to power the various components. Receiver (RX) and transmitter (TX) units provide the electrical interface between the controller block and the 2-wire interface. Figure 13B shows an exemplary arrangement of an embodiment of a sensor hub according to the specification illustrating the internal functional blocks, the sensor hub in this arrangement comprises onboard sensors 64. Figure 14 show further exemplary arrangements of a sensor hub 1 and sensor hub 101 according to embodiments of the specification and in particular illustrating the internal functional blocks. The sensor hub 1 further comprises a galvanic isolation on each sensor channel to facilitate a safe operation when the sensors are connected to different voltages. The isolation also breaks the common mode path to ground. The isolation block must isolate both power and data to the sensor interfaces. Figures 15A, 15B, 15C and 15D are block diagrams of exemplary gateway modules according to embodiments of the specification each including a communication block, and illustrating also arrangements including a sensor block and / or output block. The gateway module comprises an external communication block in addition to the module communication block. In the exemplary arrangement there is an isolation between the USB interface and the rest of the blocks. This provides an extra layer of protection. The gateway may also have additional communication interfaces such as CAN, Ethernet and Wi-Fi. Other features may include, Real Time Clock, storage memory and user interface. Figure 16 shows a simplified circuit diagram of a gateway module interfaced with a sensor hub using the 2-wire interface according to an exemplary arrangement of the specification. In this exemplary arrangement, the gateway module comprises a module communication block and an external communication block. Figure 17 shows an exemplary arrangement of a communication protocol according to the system and modules of the specification. The gateway communicates with other modules using a pulse pattern where data communications is separated from power delivery using Time Division Multiplexing. Figure 18 shows a simplified flow diagram of the interaction between a computerand a gateway with attached sensor hubs. The computer controls the network and dictates the operation via a graphical user interface. Figure 19 shows a block diagram of an exemplary arrangement comprising an external computer, multiple gateways, and 2-wire interfaces each with multiple sensor hubs and output modules. The computer connects to the gateways in this example using multiple USB interfaces. One of the gateways comprises a CAN / 12V 4-wire interface output which connects with two other gateways. Each gateway connects to sensor hubs and output modules with a 2-wire interface wherein they are all daisy chained together. Figure 20 shows an exemplary arrangement of a setting for a modular system according to an embodiment of the specification. Here two sensor hubs are placed in an environmental test chamber to measure temperatures on a HVAC under test. The computerand gateway are outside the test chamber. The gateway communicates with the hubs via the 2-wire interface. This approach significantly reduces the amount of thermocouple wiring. Figure 21 shows an exemplary application and setting for a system according to an embodiment of the specification. Here two hubs are placed inside a hazardous environment while the computer and gateway are located, about 100m away, in a control room. The low power feature of the 2-wire interface makes it suitable for reducing wiring in hazardous settings. Figure 22 shows an exemplary application and setting for a system according to an embodiment of the specification. Here an output module 11 and a sensor hub 1 are used to control a heater system which has a number of controllable zones. Figure 23 shows an exemplary arrangement of a gateway according to an embodiment of the specification which plugs into an embedded computer system such as an Arduino or Raspberry Pi. This is an alternative arrangement to the USB connectivity to a computer. Figure 24 shows an exemplary arrangement of a gateway according to an embodiment of the specification which has its components integrated into a vehicle Electronic Control Unit (ECU). The microcontroller component in the controller circuitry could be removed and the corresponding firmware be executed on the ECU microcontroller instead. This enables reduction in component count and size of the circuit board. Figures 25 and 26 show a block diagram of an exemplary output module according to an embodiment of the specification. Figures 27 and 28 are block diagrams of exemplary arrangements according to embodiments of the specification showing in Figure 27 a gateway 7 having input and output ports and input and output channels; and showing in Figure 28 an input and output module 1 having input and output ports and input and output channels. Figure 29 is a block diagram of an exemplary module according to an embodiment of the specification where a group of ports share a common galvanic isolator which provides isolation between said ports and the 2-wire interface. Detailed Description The following discussion provides many exemplary embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed. For simplicity and clarity of illustration, reference numerals may be repeated among the Figures to indicate corresponding or analogous elements. Numerous details are set forth to provide an understanding of the examples described herein. The examples may be practised without these details. In other instances, well-known methods, procedures, and components are not described in detail to avoid obscuring the examples described. The description is not to be considered as limited to the scope of the examples described herein. With reference the to the Figures, and initially in particular to the exemplary arrangements of Figure 8, Figure 9, Figure 10, Figure 11, Figures 12a,b, and Figures 27-28 the present specification provides a modular input and output system 100, shown in overview. The system 100 is a modular system that may be assembled using two or more modules 150. In an exemplary arrangement the system comprises a module test and measurement system 100, in which the modular system comprises at least a gateway 7 and a sensor hub module 1, each defining a module 150 of the system. System 100 is a modular system and the component modules 150 are configured to be flexibly arranged according to the applications or requirements. The system 100 is configured to be scalable, as required by the application needed for example, a test situation. The types of modules 150 may be effectively considered to include primary and secondary modules. The primary module comprises a gateway module 7 configured as a gateway for communication and power delivery to further connected secondary modules. The gateway further comprises means for communication with an external processor or external computer network, the processor or network being external to the modular system 100. The secondary modules comprise input / output hub modules (I / O modules) having an input or output function defined by input or output channels, or a combination of input and output channels, including as described further below. For the purposes of definition, the term “port” can refer to an input channel or an output channel or a channel that can be bidirectional. It is understood that it is possible to reconfigure ports from input to output or vice versa A port can interface to its own individual connector or multiple ports can interface to a single connector. The term sensor can also include such devices as switches and Human-Machine-Interface input devices. The secondary modules may for example include a sensor hub module 1 or 101 for receiving inputs, an output module 11 for providing control outputs to a connected load, and an input / output module 9, having both input and output channels. Various configurations of the modules are possible noting the common communication platform of the modules. For example, a sensor hub module could be configured to include an output, similarly an output module could be modified to include an input. Further, it is noted that the gateway module may further comprise one or more input channels and / or one or more output channels. The gateway module 7 essentially defines a primary module of the system and provides a gateway between further connected secondary modules such as a sensor hub module 7, output module 11, and a hybrid input and output I / O module of the system 100, and a connected processor or network. The modules 150 of the system have in common modular features that allow for their coupling and inter-connection, being configured for coupling mechanically. Each module 150 comprises corresponding mechanical connector features for coupling or mating to those of another module. The modules 150 are formed and dimensioned to further support the modular coupling thereof to other modules of the system - each module has a form and dimensions that correspond to those of other modules. That is larger modules have a footprint that is a multiple of that of a base sized module. Further, each module is configured for communicative coupling to provide data communication, and for electrical coupling to provide power between the modules. The different modules 150 have common module interface connectors and are configured to communicate via a common power and communication protocol. As such the modules configured as plug and play modules and provided as physically stackable and connectable modules. The arrangement of system 100 as a modular system advantageously provides an improved input and output, I / O, system, that allows for the coupling of a variety of inputs and outputs, and that supports a consolidated and common control, communication, and power delivery. Taking the example of a modular system according to the specification configured as a test and measurement system based on coupling of modules - such an arrangement allows for coupling of modules for flexibly extending the system or alternatively reducing the components of the system, depending on requirements. The system is reconfigurable and scalable. This allows for an increase or reduction of capacity according to requirements and allows for improved efficiency. The system 100 may include for example one or more sensor hub modules 1 configured for location as required at a test site and local or near to the sensors to which it interfaces, and one or more external gateway modules 7. The sensor hub 1 may be located remotely relative to the gateway module 7. The modular form of the test and measurement system allows for flexibility in tailoring the system and locating the required components relative to sensors at a test site. In particular, an input / output, I / O, hub module can advantageously be located remotely relative to the gateway but close to the connected sensor or loads - to allow for example multiple short connections to the remote hub and a single connector from the remote hub to the gateway. Further, a plurality of remote input / output hub modules may be connected in daisy chain connection to a gateway -which allows for further consolidation of communication and power delivery over the daisy chain configuration in a situation that might previous have required a large network of individual cables to each individual output devices and input devices. Further with reference to Figures 27 and 28 it is noted that an input / output module of the system for example a sensor hub module may comprise, in addition to input channels, one or more output channels. Again, the flexibility in configuration of the input / output modules - which fundamentally operate on the common protocol for communication and power delivery provides advantages for use in a variety of applications. The modules of the system 100 are further configured as plug and play modules which advantageously supports excellent flexibility and ease in configuration or reconfiguration for different test environments. The sensor hubs 1 are configured for plug and play connection to connected sensors or loads and to other modules - including a gateway module 7 or another sensor hub 1 or an output module 11. Modules 150 as noted above comprise corresponding mechanical coupling features for mating the modules. Further the modules may comprise a keying feature to provide for coupling of modules of similar type for ease of use and safely - for example modules configured for measuring temperatures in a low voltage setting may comprise a first keying feature. Modules configured for use in a high voltage environment may comprise a different keying feature. In addition, modules may be configured to have different colours to facilitate ease of use and safety. For example, modules configured for measuring temperatures in a low voltage setting may have a blue base housing portion or other marking whereas modules configured for use in a high voltage environment may have an orange housing base portion or other marking. These keying or colour features may be provided to allow a user to quickly identify which module should connect to which other module rather than having to read product labels on the housing. Referring to Figure 1 and Figure 13a, an exemplary arrangement of a sensor hub 1 according to an embodiment of the present specification is shown. The sensor hub 1 is also referred to as sensor hub module 1 in the specification, taking account of the modular arrangement of the components of the system 100. Referring to Figure 2 and Figure 15A an example of a gateway module 7 according to an embodiment of the present specification is shown. The sensor hub 1 and gateway module 7 are components of the modular system 100 platform which is configured to provide a common set of characteristics amongst all its member modules to enable mechanical coupling and communicative and electrical coupling for communication and delivery of power between modules 150 of system 100. Referring to Figures 22, 25 and 26 examples of output module 11 according to embodiments of the present specification are shown. The common characteristics include the data communications and power interfacing, and the corresponding connectable mechanical features of modular components. In the exemplary arrangement of the drawings including Figures 1 and 2, Figures 13A, 13B and 13C and Figures 15A to 15D, sensor hub 1 and gateway module 7 comprise two 2-pin connectors 2 for interfacing to a communications bus, and sensor interface connectors 3 for interfacing to sensors. As shown in exemplary Figure 1 the sensor hub module 1 (also referred to as a sensor hub 1) comprises a housing 160, having upper and base surfaces 161, 162, firstand second lateral ends 163, 164 and a front longitudinal side 165 and rear longitudinal side 166. The housing 160 comprises at the upper surface receivers 4 comprising recesses or apertures for receiving corresponding protrusions 5 such as protruding feet 5 located in the base surface, of a corresponding module. The receivers 4 and protrusions 5 are configured to facilitate selective fastening and mounting together with other modules of the system. The receivers 4 and protrusions 5 allow for a secure fixing of modules together, as required. The sensor hub 1 further comprises apertures 6 configured to allow for the securing the sensor hub 1 to an external fixture, for example at a remote test location or for secure fastening of a stack of modules to each other. In the arrangement of Figure 1 the upper surface 161 comprises 8 recesses. The lower surface comprises four protrusions 5, located proximal the four corners of thereto. The recesses or receivers 4 and protrusions 5 are thus configured to allow for flexibility in locating a first module relative to another to which it is to be connected. This allows for overlap of modules for example when connecting an upper module with two lower modules and having some overlap with each, or for connection of two smaller modules with a larger module. The receivers and protrusions are configured to allow snap-fitting or friction fitting for fixing together. The modules are also detachable and re-attachable at the corresponding fixing members to allow for changing the configuration and attachment of modules as required. It will be appreciated that alternative arrangements of corresponding mating members may be provided. The arrangement allows for stacking of the modules 150 and accordingly a reduced footprint of the stacked system relative to a larger dimensioned component. Reference is made to Figures 3,4 5 and 6 which illustrate various exemplary mounting configurations. Figures 13A, 13B and 13C show block diagrams of exemplary sensor hub module 1 and 101. The sensor hub modules 1 and 101 are similar. It is noted that the sensor hub module 1 is configured for connection of external sensor to input channels of the module. The sensor hub module 101 comprises internal or onboard sensor each on an individual sensor channel. The sensor hub 1 of Figure 13A defines a module 150 of the modular system 100. With reference to Figure 13A the internal functional blocks of the exemplary sensor hub 1 are described. The internal functional blocks may be considered broadly as a first communication block 180 and a sensor blocks 182. Controller 33 is configured to provide control of communication and sensing functions. The module communication block 180 comprises the components that support the module communication and power delivery functions. The module communication block defines a communication channel of the module. The sensor block 182 comprises one or more input channels or sensor channels 181 and includes the circuitry relating to the sensing functionality of the module. The communication block 180 comprises communication interface connectors 2 and circuitry comprising transmitter 31 and receiver 30 configured for receiving and transmitting data. The controller 33 provides control of the communications. The communication interfaces 2 are used for the delivery of power to the sensor hub 1 and for data communication with an external gateway module 7. In the exemplary arrangement of Figure 13A, sensor hub 1 comprises communication interface connectors 2. In the exemplary arrangements the connectors 2 comprise 2-pin connectors - that is each connector 2 has a first and a second pin. Each of the first pins may be configured for connection to a common ground. Each of the second pins may be joined together and internally connected to each of a regulator 32, receive buffer 30 and transmit buffer 31. The sensor hub 1 comprises sensor interfaces 3, signal conditioners 34 and a sensor hub controller 33. The signal conditioners 34 are also referred to as sensor signal circuit 34 and sensor circuit 34. The sensor hub 1 of the exemplary arrangement comprises input channels 181. Each input channel 181 comprises a sensor interface 3, sensor signal circuit 34 to receive and to deliver a sensor signal 610 from a connected sensor 13 to the sensor hub controller 33. The sensor interface connectors 3 are configured for connection to external sensors 13. The sensor interface connectors 3 comprise 2-pin connectors. Other embodiments may have high pin count connectors where many sensors are interfaced to a hub via a single connector. An example is shown in Figure 7 where the sensor hub module 150 has a 16-pin connector to facilitate 8 thermistors. The signal applied to the pins of one of the connectors 3 when connected to a sensor 13 will be a sensor signal 610 comprising the sensor signal received from an external sensor 13 connected to the sensor hub 1. The sensor signal 610 comprises sensor data received from an external sensor 13. The signal 610 is routed to the signal conditioning circuit 34 (also referred to as sensor circuit 34) configured to provide such functions as filtering, amplification, and analog to digital conversion. The outputs from the signal conditioners 34 i.e. the conditioned sensor signals are fed to the sensor hub controller 33 (or controller circuit 33). The controller circuit 33 is configured also to perform additional functions on the sensor signals or sensor data. The controller circuit 33 is further configured to manage the communications between the sensor hub 1 and a connected external gateway module 7. The communication is managed via the receiver 30 and transmitter 31 buffers of the communication block 180. A regulator 32 provides a stable operating voltage to the sensor hub controller circuit 33 and the other electronic circuits. Figure 13B shows an exemplary sensor hub module 101 comprising onboard sensors 64. The sensor hub module 101, similar to the sensor hub module 1 comprises a communication block 180, sensor block 182, and controller 33 operable to control sensor block and communication block operation. It will be appreciated that various alternative arrangements of sensor hub module 1,101 may be provided, for example in a further arrangement a sensor hub module may comprise one or more onboard sensors 64 and one or more externally connected sensors 13. Figure 14 shows the block diagram of a further exemplary arrangement of a sensor hub 1 according to an embodiment of the present specification. Sensor hub 1 further comprises channel to channel galvanic isolation blocks 35. These channel-to-channel galvanic isolation blocks 35 advantageously provide both a power and data barrier between the sensor circuitry 34 of each channel (181) and also a barrier to the network 2-wire interface 2 (as referred to as communication interface 2). The channel-to-channel galvanic isolation blocks 35 provided in the sensor hub 1 advantageously protect the upstream computer hardware from damage and users from electric shock in the event a sensor makes contact with a high voltage. The sensor hub 1 of the exemplary arrangement of Figure 14 has four sensor channels 181. Each sensor channel 181 comprises a sensor interface 3, sensor signal circuit 34 to receive and to deliver a sensor signal 610 from a connected sensor 13 to the sensor hub controller 33, and each channel further comprises a channel-to-channel galvanic isolation blocks 35. Thus, the hub 1 having isolated sensor channels 181 which in use in a modular system arrangement in combination with an external gateway module 7 having an isolated external communication channel 193 (described further below with reference to Figures 15Ato 15D) effectively and advantageously provides a double isolated protection barrier between the sensor 13 and the external computer 12. It will be appreciated that the external communication channel 193 may comprise different communication channel types and interface such as for example USB, Ethernet or WiFi interfaces, or other suitable interfaces. Further, the sensor hub 1 of the exemplary arrangement of Figure 29 has four sensor channels 181.Each sensor channel 181 comprises a sensor interface 3, sensor signal circuit 34 to receive and to deliver a sensor signal 610 from a connected sensor 13 to the sensor hub controller 33, via a power / Data isolation block 178 and control circuit 179, which provides galvanic isolation between the group of ports and the 2-wire interface 2. It will be appreciated a test environment may be a high voltage hazardous area. It will be appreciated that a sensor wiring could in such circumstances and application come into contact with hazardous high voltages. It is noted that a further advantage of the modular system 100, is that the arrangement of hub 1 having isolated sensor channels 181, described above with reference to the exemplary embodiment of Figure 14, is that only the isolated safe low-voltage 2-wire interface cable exits the test environment area to the external gateway module 7. This arrangement contrasts with for example rack type systems having sensor isolation circuitry within the rack system itself. Here the cabling from the sensors, which could be in contact with high voltage, must leave the hazardous and route to the rack system to obtain the electrical isolation. Such cabling could come into contact with safe low voltage cabling or the operator. It may be necessary for such rack-systems to be placed completely inside the hazardous area to achieve safe operation. This results in significant complexity, effort and cost. In some cases, the rack system may be physically too large to fit inside the hazardous area thereby making it impossible to achieve safe isolation. The compact and versatile modular system allows for selective placement of the modules in arrangements that facilitate safe isolation in many more scenarios than would be possible with for example with a rack system. Referring to Figures 2 and 15A and 15B exemplary arrangements of gateway modules 7 according to embodiments of the specification is shown. The gateway 7 (also referred to as gateway module 7 or controller 7) as noted above, defines a module 150 of the modular test and measurement system 100. The gateway module 7 is configured to comprise features and characteristics in common with other types of modules 150 of the system 100 including for communications interfacing between modules 150 to allow for coupling to other modules 150 for data communication and power supply. Further, the mechanical form and features of the external gateway module are defined to allow for physical coupling to other modules 150 of the system 100 to allow for forming of a system having the capacity required and that can be tailored to the requirements of a test location and a test project. Referring to Figure 2 and Figure 15A in the exemplary embodiment the gateway module 7 comprises a communication interface connector 2 for interfacing to a communications bus. The communication interface connector 2 comprises a 2-pin connector. The gateway module 7 comprises a module communication block 190. The gateway module 7 further comprises an external communication block 193. In the exemplary the arrangement of Figure 15A the gateway 7 further comprises a sensor block 182 and sensor channels 181. The gateway 7 comprises connectors 3 configured for interfacing to a sensor 13. The sensor block 182, and sensor channels 181 are similar to those described above with reference to the sensor hub module 1. Control of the sensor block is managed by the gateway controller 51. Similarly to the arrangements described above with reference to the sensor hub 1 having a plurality of sensor channels, the gateway module of the exemplary arrangement comprises sensor channels 181. External sensors 13 are connectable to the gateway module 7 via the sensor interface connectors 3. The signal applied to the pins of one of these connectors 3 is routed to a signal conditioning circuit 52 which can provide such functions as filtering, amplification, and analog to digital conversion. The outputs from the signal conditioners 52 are fed to a gateway controller circuitry 51 which can also carry out additional functions on the sensor signals. With reference to the arrangement of Figure 14 and Figures 15 it is noted that the sensor channels 181 of the gateway module 7 may further comprise channel to channel galvanic isolation blocks 35. The gateway module controller circuit 51, is configured to manage the communications between the gateway 7 and an external sensor hub 1 via the receiver 53 and transmitter 54 buffers. A USB connector 8 provides power and data communications with a computer. The gateway module 7 may further comprise a power isolation block 57 and a communication isolation 50 block located between the USB interface 56 and the rest of the blocks. This provides an extra layer of protection between the sensors of the system and the connected processor or computer. These features configured for external communication to a computer or network define the external communication block 193. It will be appreciated that alternative arrangements of the gateway module 7 may be provided - for example a gateway module 7 not including any sensor interfaces or sensor block. It will be appreciated that in other alternative arrangements the gateway module 7 may further include an onboard sensor in addition to a sensor connector or instead of a sensor connector. It may also include one or more output ports. Similar to the sensor hub 1, the gateway module 7 comprises a housing 170 comprising upper and lower surfaces 171, 172, first and second lateral side ends 173, 174 and front and rear longitudinal sides 175, 176. The upper surface includes recesses or apertures 4 defining receiver for receiving corresponding mating features of another module 150. The lower surface comprises protrusions 5 or protruding feet 5 configured to be received in corresponding receivers. This arrangement similar to that of the sensor hub 1 allows fastening or interconnection of a plurality of modules. The gateway further comprises a mounting aperture 6 configured to facilitate securing the gateway 7 to an external fixture for example using a screw or other fixing means. The gateway module 7 of Figure 2 further comprises LEDs 177 which are operable to provide an indication of operating state. It will be appreciated that arrangements of the gateway 7 according to the specification may include one or more connector interfaces 2 and may include additional communication blocks 190 with corresponding RX and TX circuits depending on capacity requirements and connected modules. The arrangement of Fig. 2 shows a single connector interface 2, the arrangement of Figure 15A shows two connector interfaces 2, while with reference to Figure 15B an arrangement showing two connectors 2 and two communication blocks 190 is shown. Figure 15A is a block diagram of the gateway 7 according to the exemplary embodiment and shows an internal view of the functional blocks thereof. The communication connectors 2 are configured to enable communications with external secondary modules 150 for example sensor hubs 1. The connectors 2 each have two pins namely a first pin and a second pin. In one embodiment each of the first pins are connectable to a common ground and each of the second pins are joined together and internally connected to a current limit switch 55. The second pins of the arrangement of Figure 15 are further connected to receive buffer 53 and transmit buffer 54. The mechanical form features of the modules 150, 1,7, 101 and 11 have been described above. Figures 3, 4 and 5 show various arrangements in which module 150 comprising sensor hub module 1 or gateway module 7 are physically interconnected. This is achieved by the provision of corresponding mechanical fastening features. These features comprise receivers and protrusions configured for mating. Fixing is based on friction fitting. It will be appreciated that additional or alternative mechanical fastening means may also be provided. A mated hub assembly, shown in Figure 4 in which two sensor hubs 1 are interconnected. Another example with a gateway 7 clipped into a hub 1 is shown in Figure 5. Use of the same mechanical connection system is shown in Figure 6 where a hub is attached to a mounting plate 20. Here the plate 20 is fastened to a wall or base 21 using screws and the hub 1 is attached using the same arrangement of studs 5 and sockets 4. In order to provide a more secure fastening, particularly for bases with large vibration, a cover accessory 22 can be used to lock all modules to the mounting plate 20 as shown in Figure 7. As noted above the modules 150 of the system 100 comprising the sensor hub 1 and gateway 7 are configured for coupling to provide a test and measurement system 100 tailored to the test and measurement requirements and to the location and features of the test environment. The modules 150 are configured for interconnection for communication and power delivery. The modules 150 are also configured for mechanical interconnection to allow the user to build a robust and secure system. Some exemplary arrangements are illustrated in Figures 8, 9, 10, 11, 12a and 12b described further below. Figures 15a to 15d show block diagrams of exemplary gateway modules 7 according to the specification. In the arrangement shown in Figure 15a gateway 7 comprises a 2-wire module communication block 190 and a plurality of sensor input channels 181 of a sensor block 182. A gateway 7 comprising two communication channels is shown in Fig 15b. The gateway of Figure 15B also comprises two communication blocks 190. Another arrangement of a gateway, with output blocks 192 is shown in Fig 15c. These output blocks enable a gateway to control external loads or actuators such as relays 14 or may for example be configured to provide signals to a motor controller. Figure 15d shows an exemplary gateway comprising two 2-wire communication channels and two internal sensors 64. There are no sensor input connectors or actuator output blocks in this exemplary arrangement. The internal sensors may be configured to measure temperature or acceleration, for example. The gateway of Figure 15D further comprises a 4-pin interface connector 66 configured to enable connection to a 4-wire interface which comprises two wires to connect to a CAN bus protocol and two wires to supply / receive power to / from external devices. The power could be delivered at 12V and up to 1A, however, it will be appreciated that these values should not be seen as limits of the system but rather as exemplary of a possible range of operation. It is also appreciated that a gateway could have a number of additional communication interfaces over and above the communications interface 193 and the 4-wire interface. For example, a gateway may further comprise an 8-wire interface. As discussed above the modules 150 of the modular system 100 are advantageously configured for communication and power delivery based on a common communication platform. The modules each comprise at least one module communication channel and may comprise 2 or more module communication channels. In particular, input / output modules such as sensor hub modules, output modules or modules having both input and output channels may comprise at least 2 module communication interfaces on a single module communication channel. The modules of the system may also comprise more than one module communication channel. This arrangement advantageously allows for coupling of multiple in a daisy chain configuration to a single gateway provided for communication and power delivery over the common module communication protocol between connected modules. Exemplary arrangements of extended modular systems comprising multiple connected modules are illustrated with reference to Figures 11, 12a, 12b, 19 to 22, and also Figures 8 to 10 which show external views of connected modules. Figure 8 shows an example of daisy chaining hubs and gateways together. Here a gateway 7 is connected to a first sensor hub 1 via a 2-wire cable 10. The cable 10 is plugged into one of the 2-wire interface connectors 2 in the sensor hub 1. A second 2-wire cable 10 is plugged into the second 2-wire interface connector 2 of said first hub 1 and the other end of the cable 10 is plugged into one of the 2-wire interface connectors 2 of a second hub 1. This daisy chain connection enables data to pass from any hub to the gateway. The connection similarly allows for delivery of power to the connected sensor hubs 1. Figure 9 shows an external gateway module 7 coupled with a first sensor hub 1 which is in turn coupled with another second sensor hub 1. All three modules are connected with a daisy-chain cable arrangement comprising two 2-wire cables 10. Figure 10 shows a gateway module 7 coupled with a sensor hub module 1 which is in turn mated with another distantly located sensor hub 1. All three modules are connected with a daisy-chain cable arrangement comprising two 2-wire cables 10. The distance between modules could be up to 100m. This feature is useful when measurements are required from two locations distant from each other. Figure 11 shows an exemplary arrangement of a system 100 with a computer 12 comprising a processor, a gateway 7, and sensor hubs 1, together with an output module 11. Output module 11 comprises digital outputs, or analog outputs or relays 14. Sensor hubs 1 comprise multiple external sensors 13 connected at inputs thereof. The gateway 7 is configured to communication with external computer 12 communicates with the gateway 7 via a USB interface. The computer is configured to send information for example instructions to configure the modules of the system 100, and to read data received via sensor hub 1, and external gateway 7, from sensors 13. In one example, the computer is configured to provide control instructions to change the on / off state of relays 14. Alternatively, in another arrangement when the computer has provided for set-up of the modular system then the gateway may be operated in an autonomous mode where the gateway is disconnected from the computer but can collect sensor data and store for later delivery to the external computer. In addition, in this arrangement the gateway with the associated modules may provide for control of connected loads for example an actuator or motor. With regard to the output module 11, reference is made also to figures 25 and 26 which show a block diagram of an exemplary output module. Reference is also made to exemplary input / output modules of Figures 27 and 28. The internal components are similar to those for a sensor hub module 1. However, the output module 11 comprises output blocks 202 (which may also be referred to as output channels), and a communications block 200 The output blocks are provided in the place of the sensor input channels of sensor hub 7. The output block 202 comprises an output buffer 63 which is configured to supply power and control to an external load 14. The external load 14 may be a relay or motor control unit or other suitable load as required for a particular application. The output block 202 may further comprise a galvanic isolator 65 such as an optical isolator to provide galvanic isolation between the output load 14 and the rest of the output module circuitry for example communications block 200. An output module 11 may in an alternative arrangement encompass the actual load device itself internally in the output module 11. This arrangement eliminates the need for the output channels 202. Here the internal load could be a visual / audible indicator or a small graphical display with user interface. Further, in any module having one or more channels, whether the channels are input or output channels, any of the one or more channels may comprise a galvanic isolator (35, 65) to provide isolation between that channel and any of the communications interfaces and between that channel and other channels. Similarly, a galvanic isolator may be provided on any channel of a module having a combination of input and output channels or having one or more bi-directional channels. As noted above the module may comprise at least one input port or at least one output port or a combination of at least one input and at least one output ports; and one or more of said ports may comprises a galvanic isolator (35, 65) to provide isolation between said port and any of the communications interfaces and between said port and other ports. Further with reference to Figures 27 and 28, in a further exemplary arrangement a module of the system may have both input and output functionality. Referring to Figure 27 a gateway comprising input and output ports 3 and input and output channels 181 and 202 is shown. These features are provided in addition to the module communication channel 190 and external communication channel 193 of the gateway 7 described above. The output functions and input functions are controlled by the controller 51. The gateway defines a module 150 of the system 100. Figure 28 show an arrangement of an I / O module 9 defining a module 150 of the system 100. The I / O module 9 comprise a module communication channel 180 and sensor channel 181 and output channel 202. The I / O module 9 comprises input and output ports 3. The sensor channel and output channel are similar to those already described above with reference to the sensor hub 1 and output module 11. The controller 33 provides control of the sensor block and output block. Figure 12a shows another exemplary arrangement, in which an external computer 12 is configured to communicate with the gateway 7 via a WiFi interface. It will however be appreciated that this is provided as an example and that there are other options by which a computer can communicate with the modular system and network. Figure 12b shows an Ethernet interface. It is also appreciated that networks built up using components or modules 150 of the modular system 100 can be more complex than the exemplary arrangements of the drawings, for example depending on the requirement application a system 100 may comprise multiple gateways 7 comprising multiple 2-wire interfaces 10 coupled to multiple sequences of sensor hubs 1, wherein they are all controlled by an external computer 12 - this shows the flexibility that is an advantage of the modular arrangement of the specification. In a further exemplary arrangement of the specification, the system as shown in Figure 19 is configured to include Controller Area Network, CAN, with 12V to form a 4-wire bus. An exemplary communication process between the computing device 12 also referred to as computer 12 and the gateway 7 is described in the flow diagram in Figure 18. It will be appreciated that the terms computer or computing device 12 could refer also to a mobile communication device, or other similar devices having processor and memory and on which the application can be executed. The computing device is configured to run an application which provides a display of a graphical user interface (GUI). Once the application is launched, the process includes the following: initialise 90 the gateway 7. This resets all functions in the gateway 7 to a known state, request 91 details of the network configuration. This provides the computer application with all the devices on the network and the configuration of all inputs such as sensors 13 and outputs such as relays 14. In the arrangements of the specification, as modules 150 on a modular 2-wire network share a common communication path, the gateway 7 is further configured to logically isolate each sensor hub module 7 coupled thereto such that a request for sensor data is delivered by the correct device. To support this arrangement the system 100 is configured to carry out a binary search on the unique 32-bit ID which is assigned to each module 1,7, 11, 101 at the time of production. Once the module, with the corresponding ID is found, it is assigned a short 8-bit or 2-bit address which is then used, during requests for sensor data, to select a sensor hub module to send its data. The unique 32-bit ID in conjunction with a binary search algorithm advantageously eliminates the need for a manual assignment of addresses to modules 150 before they can communicate on a network or in a modular system 100. This arrangement is advantageous in a laboratory setting where modules are often required to be plugged in and out into different networks. In such settings, to manually configure the network address every time is time consuming and increases resource requirements. For example, the MODBUS, CAN and LIN protocols require that any module, which communicates on its respective network, be assigned an address by the user. Other protocols require the user to manually define a table of all devices on the network where such devices are addressed by their unique ID. Therefore, the arrangement of the present specification which provides a modular “Plug and Play” system is advantageous - in the arrangements described no user intervention of network addressing is required to enable data transmission. The system does allow the user to assign a short 8-bit alias to the unique 32-bit ID to make it easier identify modules in a lab environment. Referring to Figure 18 that exemplary operation further includes the following step: display 92, a graphical image of the network for example in the GUI step 93, the user can then make changes to the configuration, such as change sensor type, and then download the updated configuration to the gateway 7 which will in turn update the sensor hubs 1 and output modules 11 on the network. Once the configuration is completed the data logging process can start. data collected 94 from the gateways and sensor hubs can be stored to disk as a comma delimited file or spreadsheet format and the data can also be displayed on the GUI. Features such as alarms, when values go out of bounds, could also be implemented in the computer application. steps 95 and 96 form a loop where data is requested from the gateway 7 on a timed interval basis and the retrieved data is then stored and displayed. The user can also modify ongoing operation of the gateway 7, such as switching off sensors 13 not needed. It will be appreciated that other algorithms are possible in relation to the usage of the system. The system 100 is also configured to carry out concurrent measurements. For example, when measuring temperature with multiple thermocouples 13 such as in the exemplary arrangements, the system 100 is configured to sample all sensors 13 at the same time rather than polling each one in turn. This is an advantage when examining heat flow in a device under test (DUT) where any delay from one sensor measurement to another will generate errors in the dynamic profiling. An exemplary arrangement of the specification is described with reference to Figure 16, which shows circuitry configured to enable communication between the gateway 7 and the sensor hub 1 (or a connected output module 11). A corresponding pulse waveform of the communication protocol is shown in Figure 17 to further illustrate the configuration for communication between modules 150 of the modular system 100. The communication method 600 is based on the concept of a time division multiplexing of power and data, this method further described below is also referred to in the specification and drawings as TDM-PD for ease of reference. This communication of power and data as described on the two- wire interface arrangement of the module communication channels 180, 190 is clearly different to prior arrangements using the ‘1-wire type’ protocol. As noted above, data and power are delivered via the communication interfaces between the connected modules. The system is configured to provide a controlled delivery of data and power between the connected modules. The system is configured such that: the data and power are delivered separately inside short time segments. A small fraction of power may be delivered during the data phase but the bulk of the power is delivered during the “Power Delivery” phase. In the exemplary arrangement of the waveform of Figure 17 it can be seen from the waveform 70 that data is delivered in a first-time segment 71 and power is delivered in a second time segment 72. The duration of the segments 71, and 72 can be varied according to the power demands of the modules on the 2-wire interface over a 2-wire cable 10. The power delivery phase could occur after the transmission of each bit or a sequence of bits. This method 600 of delivery of power together with data on a 2-wire bus advantageously eliminates the need for modulation, which has the further advantages of reduction in resource demands and costs. It will be appreciated that modulation is expensive to implement. The arrangement of the communication method 600 is based on a non-modulated communication protocol. Therefore, for the communication method 600 no additional features or processes are required to provide modulation - as would typically be seen in prior systems. The arrangement of the systems of the invention therefore also advantageously provide for a relative simplification in terms of system requirements i.e. that modulation is not required with the related advantages of providing an alternative non-modulated communication and a reduction in resource requirements. The TDM-PD of the present specification and invention is advantageously relatively low cost and suited to applications where power demands on the 2-wire bus are low. Advantageously, this method of delivering power with data on a 2-wire bus eliminates the need for modulation. The arrangement is non-modulated. Modulation can often be expensive to implement including taking account of required magnetics. Therefore, the arrangements of the specification are advantageous from the point of view of providing resource saving. Advantageously, the TDM-PD is very lowcost and suited to applications where power demands on the 2-wire bus are low. Further, the arrangement operates at low voltages, for example 5V, which it makes it suited to low-cost embedded systems. In more detail the arrangements of the system of the specification achieve high efficacy data transmission by firstly transmitting two data bits for every PWM pulse and secondly by keeping the protocol overhead low. The former is achieved by assigning one of four different pulse widths to each of the binary bit patterns ‘OO’=O, ‘01-1, ‘10-2 and ‘11-3. The latter is achieved by prefixing the data request to the modules, on the 2-wire bus, with a packet code (value can be 0, 1, 2 or 3) which is understood by all modules on the network which data should be transmitted. The system facilitates reconfiguration of this code and while this takes a number of data bytes to setup it is seldom done. The arrangement is advantageously in comparison with other protocols, for example, LIN, CAN, TCP / IP, have fixed message headers which contain many bytes which are always transmitted when requesting data from modules. A feature which consumes unnecessary bandwidth if the message header doesn’t change from one request to another. In contrast, the arrangement of the specification allows these long message headers to be replaced by a configurable 2-bit code which occupies only one PWM pulse. This is an advantageous feature when the baud rate is low, for example 20kbps. In further detail, in an exemplary arrangement with reference to Figure 16 of an embodiment of the present specification the TDM-PD is implemented on the controller side based on the configuration of a combination of key features, as follows. During the data phase 71, a transmitter 54 generates a PWM waveform where the width of the pulse determines the value of the data bits. For example, a 50us low pulse could represent a binary bit as T and a 100us pulse could represent a binary bit as ‘O’. Similarly, a pulse could represent two binary bits, where 50us represents a ‘11’, 100us represents a ‘10’, a 150us pulse represents a ‘01’ and a 200us pulse represents a ‘00’. A sequence of pulses combine to make up the total value of the transmitted number. The gateway 7 comprises a resistor RL 61 and capacitor CF 60 to provide line balancing and filtering to reduce electromagnetic noise. When data is not being transmitted and power is being delivered, the transmitter 54 is set to logic high output and the current limit switch 55 is turned on. It provides a low impedance path for the 5V supply to power the modules on the 2-wire network. The current limit prevents large current spikes on the 2-wire network and therefore helps reduce electromagnetic noise. When data is being received by the controller, it turns off the transmitter 54 and the current limit switch 55. A resistor 59 keeps the voltage pulled up towards 5V and has high enough resistance such that it can be pulled to ground by the hub 1 which is transmitting data back to the gateway. The receiver 53, in the gateway module 7, is used to buffer the PWM pattern, generated by the hub, and feed it to the controller circuit 51 for decoding. An additional feature of an exemplary arrangement of a sensor hub is that it may be configured to initiate a communication with a gateway by pulling down the data / power voltage to ground during a long “Power Delivery” phase as would be the case if the gateway module did not poll the sensor hub modules on a regular basis. This may be achieved by a providing a second TX block which has a much lower RL. This effectively forces more current through the current limit switch until it reaches saturation and hence results in a low pulse on the communication line. This pulse is then detected by the gateway and it can then initiate a data communications with the sensor hub. The system uses a higher value for resistor 59, in contrast to other protocols such as LIN, in order to minimise the power during data transmission. However, such a high resistance can cause a problem with data integrity when the 2-wire interface uses long cables, with corresponding high capacitance. The gateway is configured to resolve this problem by sending a calibration sequence, comprising two pulses of different width, and deriving a capacitance correction factor which is then applied to each received data pulse. In an alternative arrangement, the circuitry of the communication interface 2 may be configured to act as a digital input / output or analog input. Such flexibility in the configured and use of the interface is useful if for example a gateway 7 requires a single sensor input channel and hence in an exemplary arrangement does not need to be connected to additional sensor hubs 1. Further, it allows a gateway 7 to be configured to use the communication interface 2 to switch on / off devices, for example relays, in the event that the communications feature is not required. This is an advantage of the gateway 7 over other systems and protocols where a communications port 2 or communication interface 2 is necessarily dedicated to only one function. This further demonstrates the flexibility of the modular system of the present specification. The sensor hub 1 is connected to the 2-wire bus using a 2-pin connector 2 and must separate the TDM-PD signal into its data and power components. A regulator block 32 comprises a diode 39 and capacitor 38 which filter out the pulse pattern to leave a steady DC voltage which is fed to a voltage regulator 40 which in turn provides a stable regulated voltage to the circuitry inside the hub. The capacitor 38 provides the energy store for the hub 1 during the data phase of the TDM-PD signal. The hub is configured to transmit data by switching on / off its transmitter 31. A resistor RL and capacitor CF provide line balancing and reduces electromagnetic noise on the 2-wire bus. A transient voltage suppressor (not shown) may also be placed across the pins of the connector 2 to limit transient and surge voltages from damaging internal components. The sensor hub controller 33 controls the operation of the hub 1 including generating data PWM pulses and reading sensor 13 values. The signal conditioning circuits 34 reduce noise from the sensors before analog to digital conversion. It can be seen that the communication system of the modular system of the present specification advantageously does not rely on custom integrated circuits, as is the case with other protocols. Instead, it uses low cost discrete and simple logic components. A low cost 8-bit microcontroller implements the protocol on the modules and hence allows for flexibility of implementation. Eliminating the magnetics from the protocol implementation results in reduction of space used on the printed circuit boards. It will be appreciated that the circuit blocks of the modules, could be physically reduced by incorporating the components of said circuits into one or more integrated circuits, without affecting the functionality. Figure 20 shows an exemplary arrangement of the modular system in a test application. Here two hubs 1 are placed in an environmental test chamber 80 to measure temperatures on a HVAC 81 under test. The computer 12 and gateway 7 are outside the test chamber. The gateway 7 communicates with the hubs via the 2-wire interface 10. Each hub has a plurality of sensors 13 which measure temperatures at various points on the HVAC. The wires from these sensors 13 are short as they need only connect to the hubs 1 which advantageously locatable are local to the measurement sites. The wires from the sensors 13 do not need to pass through the wall of the chamber 80 to the outside, as in prior type arrangements. Instead, according to the arrangements of the specification, a single cable with 2-conductors 10 is all that is required. This approach advantageously significantly reduces the amount of sensor wiring relative to other test systems. Another application of a system 100 according to the present specification is shown in Figure 21 where two sensor hubs 1 are deployed measure temperature inside a hazardous area located some distance from a control room. As described above the system according to the specification includes sensor hubs 1 configured to have channel to channel and channel to ground isolation voltages of 2kV which makes them particularly suited to measurement of signals sitting on high voltages while at the same time requiring only 2-wires to provide power and communications. Figure 22 shows how an application of a system 100 according to the present specification in which a heater system is controllable by means of an output module 11 and a sensor hub 1. Here the output module 11 is configured within the system 100 to control to switches on / off relays or power semiconductor switches which in turn switch the heater voltage to the heating elements. The sensor hub 1 is configured within the system 100 to measure the temperatures on the output air flow and send the values back to the gateway 7 which in turn determines the on-time of the switches. The gateway 7 according to the arrangements of the specification can further be configured to be used as an add-on module for embedded computers such as an Arduino or Raspberry Pi as shown in Figure 23. Here the gateway 7 further comprises interface pins to enable insertion into the embedded computer and provides the 2-wire interface capability. Hence the embedded computer is then able to communicate with sensor hubs 1 and output modules 11. A further level of integration of the modular system 100 according to the specification is shown the exemplary arrangement of Figure 24. The hardware components comprising a gateway 7 in this exemplary arrangement placed on the same circuit board as a vehicle Electronic Control Unit (ECU). In some cases, the microcontroller on the gateway module can be removed and its firmware transferred to the ECU microcontroller, providing more space saving. The ECU will then be able to read multiple sensors over a 2-wire Power / Data interface via the sensor hubs. Advantages of the system of the specification The arrangements of the specification allow a flexible arrangement of sensor hub modules 1 and gateway modules such that they can be electrically and communicatively coupled, and at the same time the sensor module can be located separately from gateway and in particular that the sensor hub module can be in located close proximity to the source of the measurements i.e. close to the test site. In this way the sensor wiring from multiple sensors does not need to be routed to a single location (e.g a gateway) but can be concentrated locally near the sensor hub. In turn the sensor signal data is communication from the sensor hub to the external gateway via a single 2-wire cable. This also means the computer controlling the system 100 can be distant from the sensor or test chamber, in a clean environment, and isolated from the source of the measurement signals. The arrangements of the specification therefore support and provide a reduction in the requirements for wiring relative to prior test and measurements systems. It will be appreciated that the arrangements of the specification also have general applications where there is a need to reduce wiring from sensors to gateways. As a further advantage it was noted that the system 100 is configurable to operate at low voltage and low power thereby making it cost effective to implement and suitable for battery powered applications. In addition, in contrast to the prior type rack or chassis system, the sensor modules of the modular system of the present specification do not need to be fixed to an external support rail but instead are configured to be highly portable. Advantageously, the system 100 does not require a costly chassis to support the sensor modules. Further, it is advantageous that the modules 150 are configured to mechanically interconnect with each other, in a stacked arrangement with neat inter-wiring, thereby resulting in a complete and compact modular system structure that can be formed taking account of the space available to accommodate the system. The arrangement of the invention advantageously provides for a reduction of wiring required in comparison with prior test and measurement systems. It will be appreciated that the arrangements of the invention could also be used in more general applications where there is a need to reduce wiring from sensors to gateway. Overall, the arrangements of the present specification are directed to overcome disadvantages of prior systems by providing a system which comprises, but not limited to, gateway modules and sensor hubs. The system, of course, can also include modules with analog and digital outputs for control of various devices, gateways communicate with sensor hubs with a 2-wire interface which operates at a low voltage e.g. 5V. This makes it easy and low cost to implement the gateway circuitry in embedded systems which generally have 5V and 3.3V supply voltages on board. Some protocols such as HART and Foundation field bus require higher voltages (typically 24V) for operation and hence results in greater cost. Also, while prior systems can require power conditioners or specialised magnetic components and / or specialised integrated circuits to enable power and data travel on a single pair of wires. The present invention uses standard electronic discrete components with a simple 8-bit microcontroller to implement the communication protocol according to the embodiments of the specification. This results in a relatively lower cost and highly flexible solution as provided by the system of the present specification. It will be appreciated that in an alternative arrangement according to embodiments of the specification for use in application having greater power or bandwidth requirements sensor hub module 1 and external gateway module 7’ may further comprise one or more 4-wire interfaces 66. The 2-wire interface 2 of embodiments of the specification would typically be operated at a current limit of 20mA and bandwidth up to 20kbps. The 4-wire interface 66 is configured to use a high speed bus e.g. CAN or Ethernet and a higher voltage / current supply for example typically 12V@500mA. The other features and advantages of the sensor hub and gateway and the modular system discussed herein apply also to the sensor hub 1 and gateway 7. In addition to communicating with sensor hubs and output modules, the gateway can also communicate with a computer using USB, Ethernet or WiFi. The modules within the system mechanically interconnect using a stud / socket arrangement which provides a quick temporary fastening without the need for tools or additional fasteners. The modules can also be permanently fastened using a bolt / nut or latching clip arrangements, but these methods may require additional fasteners and / or tools. The sensor hubs can cater for a multitude of sensor types. One sensor hub can be designed to read thermocouples while another is designed for digital input signals. In addition, sensor hubs can be different sizes (scalar of a base dimension) to accommodate small / large quantities of sensors. It can be seen that the system becomes very flexible and efficient with the user having just the right amount of hardware that is needed for the application. If more measurements are needed than an extra sensor hub is just added to the stack. Another feature of the system is that hubs have two 2-pin connectors which enables daisychaining one hub to the next. This provides a further reduction in wiring. In one embodiment, a sensor hub comprises two 2-pin connectors, a plurality of sensor interfaces, a series of holes (on the top of the enclosure), four feet (on the bottom of the enclosure) and internal electronic circuitry. One of the 2-pin connectors can be connected to 2-wire cable which goes to a gateway and the second 2-pin connector attaches to another 2-wire cable which goes to another sensor hub. The internal electronic circuitry comprises a regulator, a transmit buffer, a receive buffer, a controller block and a signal conditioning circuit for each of the sensor interfaces. The signal conditioning circuit can provide filtering, amplification and digitization of the sensor signal before it is sent to the controller circuit. The controller circuitry can also digitize the sensor signals where this is not performed by the signal conditioner. The controller circuit also manages the communication flow from the hub to the external gateway module. The protocol used by the system could be any standardised 2-wire power / data implementation or a proprietary design which incorporates suitable voltage levels and timing to support the communications while powering the hub from a gateway.

Claims

1. A low power scalable plug and play modular input / output, I / O, system (100) configured to provide communication and power delivery between a plurality of connected modules (150) of the system, the system comprising:- a primary gateway module (7) having at least one module communication channel (190) comprising a 2-wire interface (2);- at least one secondary module comprising an input / output, I / O, module (1,9,11) having at least one module communication channel (180) comprising a 2-wire interface (2) for coupling said secondary module to the primary gateway module (7), each 2-wire interface being configured to provide power delivery and data communication between connected modules together on a 2-wire bus; andwherein the system (100) is configured to deliver power and data between modules (150) based on a time division protocol, power and data being delivered separately in short time segments, and the duration of the segments being controllable according to the power demands of the modules (150).

2. The system of claim 1, wherein said secondary I / O module comprises a sensor hub module (1) comprising:a sensor hub module controller (33) configured to receive sensor signals from one or more sensors coupled to the sensor hub module (1), and to communicate the sensor signals to the gateway module (7).

3. The system of claim 1, wherein said secondary I / O module comprises:(i) an output module (11) comprising one or more outputs for driving loads, the output module configured to provide output control signals from the gateway module (7) to connected devices or loads; or(ii) an input and output module (9) having one or more input and output ports, the input ports being configured for connection to sensors to receive sensor input, and the outputs being configured for driving loads.

4. The system of claim 1, the gateway module further comprising a gateway controller (51) configured to control the communication and power delivery between the gateway module and connected secondary modules, and further configured to control communication between the gateway module (7) and an external computing device or network.

5. The system (100) as claimed in claim 1, wherein the gateway module (7) further comprises: a communication circuit block comprising one or more module communication channels (190) and one or more communication interfaces (2) for coupling to modules (150) of the system (100), a transmitter and receiver, and a power delivery circuit, the communications between modules coupled to the gateway being managed by gateway controller (51).

6. The system as claimed in any preceding claim, the gateway module further comprising an external communication channel (193) for communication of signal data received from connectedmodules (150) of the modular system (100) to an external computing device or network and for communication of signals from the external computing device or network to the modular system.

7. The system of claim 6, wherein the external communication channel (193) comprises an isolated channel configurated to isolate the communication channel from the other components of the gateway.

8. The system of any preceding claim, wherein the communication circuit block of the gateway module comprises at least one 2-wire interface, and further comprising one or more interfaces comprising at least 4-wires.

9. The system of any preceding claim, wherein the power and data are delivered in a nonmodulated manner.

10. The system of any of claims 2 to 9, wherein the sensor hub module (1) comprises one or more internal sensors (64) mounted onboard the sensor hub.

11. The system of any of claims 2 to 10, wherein the sensor hub module (1) comprises: one or more sensor channels (181) each comprising a sensor connector (3) configured as a sensor input for coupling to an external sensor (13) to receive a sensor signal for delivery to the sensor hub module controller (33) via corresponding sensor channel (181).

12. The system of claim 11, wherein each sensor channel (181) comprises a sensor signal circuit (34) and wherein the sensor signal is communicated via the sensor signal circuit (34) to the sensor hub controller (33), and wherein the sensor signal circuit (34) is configured to provide signal conditioning including one or more of filtering, amplification, and analog to digital conversion.

13. The system (100) as claimed any of claims 2-12, wherein the sensor hub module (1) further comprises:a sensor block (182) comprising sensors or sensor channels, and arrangements for processing received sensor signals; anda communication circuit block (180) comprising the at least one interface connector (2) for communication with other connected modules comprising one or more of a gateway module, a sensor hub module, an output module or an input / output module.

14. The system of claims 2 to 13, wherein the sensor hub module comprises one or more sensor channels (181) each sensor channel further comprising a channel-to-channel galvanic isolator (35), wherein the galvanic isolator (35) is configured to provide a power and data barrier between the sensor signal circuits (34) of each channel, and between the sensor channels (181) and any communication interface.

15. The system of any preceding claim, further arranged according to one of the following: (i) wherein the module comprises at least one input port or at least one output port or a combination of at least one input and at least one output ports; wherein one or more of said ports comprises at least one galvanic isolator (35, 65) to provide isolation between said port and any of the communications interfaces and between said port and other ports;(ii) wherein the module comprises at least one input port or at least one output port or a combination of at least one input and at least one output ports; wherein all said ports share a galvanic isolator (178) to provide isolation between said ports and any of the communications interfaces.

16. The system of any preceding claim, wherein the system (100) is configured to deliver data and power separately inside short time segments, the data being delivered in a first time segment (71) and power being delivered in second different time segment (72), wherein the duration of the segments being controllable according to the power demands of the modules (150) on the 2-wire interface (2).

17. The system of any preceding claim, wherein the gateway module (7) is configured to implement the time division delivery of data and power, wherein the gateway module comprises a transmitter (54) configured to route a waveform having first- and second- time segments generated by the controller circuit (51).

18. The system of claim 17, wherein the controller (51) is configured during a first data phase time segment to generate a waveform wherein the width of the pulse determines the value of the data bits.

19. The system of claims 17 to 18, wherein when power is being delivered, the transmitter (54) is set to logic high or floating output, and a current limit switch (55) is turned on to provide a low impedance path to provide power to the modules on the 2-wire network.

20. The system of any preceding claim, wherein the secondary I / O module is configured to separate the received power and data signal into its data and power components, the secondary I / O module further comprising a regulator (32), and a receive buffer (30), wherein the secondary modules of the system may comprise a sensor hub module (1), an output module (11) or an input / output module (9).

21. The system of any preceding claim, wherein the gateway module (7) is further configured to detect the capacitance of the 2-wire interface between the gateway module and connected I / O modules and to generate a capacitance correction factor to correct for distortion, due to capacitance, in a signal received from the connected I / O module.

22. The system of any preceding claim, wherein one or more of the secondary modules comprise:a second module communication interface connector (2) configured for coupling a first secondary module to a second secondary module of the system in a daisy chain configuration;wherein each interface connector (2) comprises a 2-wire interface connector, configured for delivery of power and data based on a time division protocol, wherein data and power are delivered separately in short time segments and wherein the duration of the segments is controllable according to the power demands of any connected secondary modules.

23. The system of any preceding claim, comprising one or more secondary modules including at least one sensor hub module, wherein the sensor hub module is locatable remotely in a test environment such as a test chamber, and configured to receive sensor signals from a plurality ofsensors and to communicate said sensor data back to the gateway module via a common 2-wire connection, togetherwith power delivery and any digital output communication.

24. The system of claim 23, wherein the sensor hub module is configured for coupling to a plurality of external sensors at one or more sensor channels to receive sensor signals on a plurality of sensor channels and to deliver the sensor data to the connected gateway together on a common 2-wire connection, togetherwith power delivery and any digital output communication.

25. A sensor hub module (1) of a modular input and output system comprising:a first module communication interface connector (2) configured for coupling the sensor hub module (1) to another gateway module of the system;a second module communication interface connector (2) configured for coupling the sensor hub module to a further secondary module of the system in a daisy chain configuration;a sensor hub module controller (33) configured to receive sensor signals from one or more sensors coupled to the sensor hub module (1), and to communicate the sensor signals to the gateway module (7);wherein each interface connector (2) comprises a 2-wire interface connector to provide power and data communication;wherein the system is configured to operate at low power and low voltage, the power and data being delivered together on a 2-wire bus;wherein the system (100) is configured to deliver power and data between modules (150) based on a time division protocol, power and data being delivered separately in short time segments, and the duration of the segments being controllable according to the power demands of the modules (150).

26. An output module (11) of a modular input and output system comprising: a first module communication interface connector (2) configured for coupling the output module (11) to a gateway module of the system directly or via a daisy chain connection via other modules of the system;a second module communication interface connector (2) configured for coupling the output module to a further secondary module of the system in a daisy chain configuration;an output module controller (33) configured to communicate the control signals received from the gateway module to a connected load;wherein each interface connector (2) comprises a 2-wire interface connector to provide power and data communication;wherein the system is configured to operate at low power and low voltage, the power and data being delivered together on a 2-wire bus;wherein the system (100) is configured to deliver power and data between modules (150) based on a time division protocol, power and data being delivered separately in short time segments, and the duration of the segments being controllable according to the power demands of the modules (150).

27. An input / output, I / O module (9) of a modular input and output system comprising:a first module communication interface connector (2) configured for coupling the I / O module (9) to a gateway module (7) of the system directly or via a daisy chain connection via other modules of the system;a second module communication interface connector (2) configured for coupling the I / O module to a further secondary module of the system in a daisy chain configuration;one or more input channels (13) and one or more output channels (14);an I / O module controller (33) configured to communicate the control signals received from the gateway module to a connected load, or to communicate an input signal received from a connected input to the gateway module;wherein each interface connector (2) comprises a 2-wire interface connector to provide power and data communication;wherein the system is configured to operate at low power and low voltage, the power and data being delivered together on a 2-wire bus;wherein the system (100) is configured to deliver power and data between modules (150) based on a time division protocol, power and data being delivered separately in short time segments, and the duration of the segments being controllable according to the power demands of the modules (150).

28. A gateway module (7) of a modular input and output system comprising:one or more module communication interfaces (2), wherein the or each communication interface (2) being a 2- wire interface configured to couple the gateway to a secondary module of the system to provide power and data communication between the gateway and the connected module, wherein power and data are delivered together on a two-wire bus;a controller configured to control power delivery and communication with connected modules (150) based on a time division protocol;wherein data and power are delivered separately in short time segments and wherein the duration of the segments is controllable according to the power demands of the modules (150) on the multiple-wire interface (2).

29. The sensor hub module of claim 25, the output module of claim 26, the I / O module of claim 27 or the gateway module of claim 28, further comprising:a sensor block (182) comprising sensor channels comprising an onboard sensor, and / or at least one sensor interface connector configured for coupling to one or more external sensors, the sensor block coupled with the controller (51,33) of the module which is configured to receive sensor signals and to provide communication of sensor signals; anda communication circuit block (180) comprising the at least one interface connector (2) for communication with other connected modules comprising one or more of a gateway module, a sensor hub module, an output module or an input / output module.

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