Radar level gauge system and method for controlling a radar level gauge system

Abstract

The radar level gauge system (200) comprises: a communication module (202) configured to be connected to an external communication device; a measurement module (204) configured to generate, send and receive measurement signals; a control connection (206) configured to connect the communication module to the measurement module, the control connection being configured to be in a high impedance mode at least during measurement by the measurement module; a power supply (208) configured to provide power to the measurement module; an energy storage (210) coupled to the power supply; a measurement connection (212) connecting the communication module to the energy storage, wherein the energy storage is arranged to be charged via the measurement connection and is configured to provide power to the power supply for measurement by the measurement module; and a switch (214) arranged between the communication module and the energy storage, the switch being controllable to disconnect the measurement connection between the communication module and the energy storage during measurement by the measurement module.

Description

Technical Field

[0001] The present invention relates to a system and method for improving the electromagnetic immunity of a radar level gauge. Background Art

[0002] Field devices are commonly used in industry to measure various process variables (eg, pressure, temperature, flow, or product level). In particular, radar level gauge systems can be used to measure the level of a product such as a process fluid, a granular compound, or another material.

[0003] In a radar level gauge system, an electromagnetic transmit signal can propagate from a transceiver arranged at the top of the tank toward the surface of the product in the tank, and an electromagnetic reflection signal generated from the reflection of the transmit signal at the surface returns to the transceiver. Based on the transmit signal and the reflection signal, the distance to the surface of the product can be determined, from which the level of the product in the tank can be inferred.

[0004] In many facilities (e.g., process industry facilities) where field devices are used, there is existing wiring between the field devices and a remote location (e.g., a host). The existing wiring typically forms a two-wire current loop for communication of commands from the host to the field device and a measurement signal indicating a process variable from the field device to the host. Communication on the two-wire current loop can be performed by controlling the current flowing through the loop. In a 4mA to 20mA loop, for example, the measurement signal can be the loop current itself. As an alternative or supplement to such an analog current level, for example, the HART protocol (highway addressable remote transducer) can be used to convey digital information by modulating the loop current.

[0005] In addition to being able to receive and send signals through a two-wire current loop, a field device may need to be able to operate using power drawn from the two-wire current loop. In other words, the field device may be a loop-powered field device.

[0006] For example, radar level gauge systems are used in the oil industry and other applications where the measuring circuit must comply with Ex (explosion proof) requirements, which makes it difficult to meet the specified EMC (electromagnetic compatibility) levels.

[0007] The primary issue to be addressed is typically conducted immunity, as radiated immunity can be addressed by requiring the can or container to be made of an electromagnetic shielding material (e.g., metal).

[0008] For example, conducted interference can be handled by adding filtering at the wired connections or by introducing galvanic isolation of the most sensitive parts of the measurement circuit, which can then be optionally grounded to the tank ground. The efficiency of the former approach is often limited due to Ex requirements, as the permissible levels of energy storage components (i.e. capacitance / inductance) are strictly restricted. This is particularly true at the relatively high voltage levels applicable at the transmitter supply terminals, i.e. the amount of filtering that can be achieved may simply not be sufficient. The latter approach significantly increases the cost and / or complexity of the system. Summary of the invention

[0009] In view of the above-mentioned and other disadvantages of the prior art, it is an object of the present invention to provide a radar level gauge system that solves the problems associated with conducted interference.

[0010] According to a first aspect of the present invention, there is provided a radar level gauge system, comprising: a communication module configured to be connected to an external communication device; a measurement module configured to generate, send and receive measurement signals; a control connection configured to connect the communication module to the measurement module, the control connection being configured to be in a high impedance mode at least during measurement by the measurement module; a power supply configured to provide power to the measurement module; an energy storage coupled to the power supply; and a measurement connection connecting the communication module to the energy storage. The energy storage is arranged to be charged via the measurement connection and is configured to provide power to the power supply to perform measurement by the measurement module.

[0011] The system further comprises a switch arranged between the communication module and the energy storage, which switch can be controlled to disconnect a measurement connection between the communication module and the energy storage during measurement by the measurement module.

[0012] The invention is based on the recognition that a radar level meter capable of handling specified EMC levels can be realized by arranging an internal energy storage controlled by a switch so that an external measurement connection can be disconnected during measurement. Since the measurement connection is used to supply power to the energy storage, the measurement connection is a low impedance connection to avoid power losses. By disconnecting the measurement connection between the communication module and the energy storage during measurement, conducted interference is prevented from reaching the measurement module during measurement.

[0013] Furthermore, the control connection, which is separate from the measurement connection, is in high impedance mode at least during measurement by the measurement module, which should be interpreted as meaning that the impedance of the connection between the communication module and the measurement module is sufficiently high to prevent conducted interferences from reaching the measurement module, at least to the extent that the measurement is not negatively affected by any interference reaching the measurement module via the control connection or via the measurement connection.

[0014] The described radar level meter can provide advantageous EMC properties at low cost and low complexity compared to conventional galvanic isolation solutions comprising, for example, the use of transformers.

[0015] According to one embodiment of the invention, the measuring connection is a connection advantageously having an impedance, which is suitable for providing power from the communication module to the energy storage. The measuring connection is a connection between the communication module and the measuring module, which is also used to provide power to the energy storage and subsequently to the measuring module. In order to charge the energy storage via the measuring connection, it is important that the impedance of the measuring connection is not too high, because the high impedance will cause power losses in the connection when energy is transferred from the communication module to the energy storage. As seen from the input side of the communication module, the suitable impedance for the measuring connection can preferably be less than hundreds of ohms, for example, less than 300Ω. In addition, the impedance between the output side of the communication module and the energy storage is preferably as low as possible by the switch. However, the suitable total impedance of the measuring connection can also be based on the configuration of the measuring module.

[0016] The switch may also be provided in the form of a controlled current regulator which allows a current up to a predetermined threshold current to pass in the on-state and presents a sufficiently high impedance in the off-state to reduce interference.

[0017] According to one embodiment of the present invention, the control connection can be advantageously configured to be controllable between a low impedance mode and a high impedance mode. Thus, for example, the control connection can be controlled to operate in a low impedance mode during an idle period when no measurement is performed and can be configured to operate in a high impedance mode during measurements by the measurement module. For example, the impedance of the control connection can be controlled by controlling the input impedance of the communication module, the input impedance of the measurement module, or the input impedance of both. In order to control the impedance, the communication module, the measurement module, or both can be provided with a tri-state buffer or a general purpose I / O (GPIO), wherein the impedance of the input / output is controllable.

[0018] According to one embodiment of the invention, the high impedance mode of the control connection is preferably adapted to have a sufficiently high impedance to prevent the propagation of conducted interference to the measurement module via the control connection. In particular, the high impedance mode of the control connection is preferably adapted so that any interference conducted via the control connection and reaching the measurement module is suppressed to a sufficiently low level so as not to have a negative impact on the measurement. For a given application, the conducted interference is preferably lower than the useful echo signal of the radar level gauge. In addition, the conducted interference is preferably lower than the inherent noise level of the measurement circuit system.

[0019] According to one embodiment of the invention, the impedance of the control connection in the high impedance mode is preferably at least 10 times the impedance of the control connection in the low impedance mode. Thus, conducted interferences can be suppressed in the high impedance mode.

[0020] According to one embodiment of the invention, the communication module is advantageously configured to control the control connection to operate in a high impedance mode or in a low impedance mode. Thus, the impedance of the control connection can be coordinated with the measurement performed by the measurement module. In addition, a command to set the control connection in either mode can be received by the communication module from an external device. An advantage of being able to switch the control connection between a high impedance mode and a low impedance mode is that the low impedance mode allows for a higher bandwidth of, for example, a clock signal, while the high impedance mode provides the required protection from conducted interference.

[0021] According to one embodiment of the invention, the control connection is an optical connection. The advantage of using an optical connection is that it is not affected by electrical interference, thereby preventing conducted interference from reaching the measurement module.

[0022] According to one embodiment of the invention, the switch may also be configured to be controlled by the measurement module to disconnect the communication module from the power supply during measurements performed by the measurement module. By arranging the switch to be controlled by the measurement module, the switch may be controlled to be open only when measurements are performed. Furthermore, the switch may be controlled to be closed again immediately once the measurement is completed, thereby maximizing the time that the switch is closed and therefore maximizing the time to charge the energy storage.

[0023] According to one embodiment of the invention, the switch may be a semiconductor switch. The switch may also be an electromechanical relay. There are advantages associated with both types of switches, and the type of switch used may be based on various system parameters and requirements.

[0024] According to one embodiment of the invention, the system may further comprise a second switch arranged to disconnect the control connection between the communication module and the measurement module. The second switch may then be controlled to be open circuit during measurement, thereby preventing conducted interference from reaching the measurement module. The switching functionality of the first switch and the second switch may be provided by a single integrated switch unit.

[0025] According to an embodiment of the invention, the measuring module is configured to be placed in a low power mode during charging of the energy storage. By minimizing the power consumption of the measuring module, the time for charging the energy storage can be minimized.

[0026] According to one embodiment of the present invention, for example, the communication module may advantageously be configured to connect to a 4 mA to 20 mA current loop interface using the HART communication protocol.

[0027] According to a second aspect of the present invention, there is provided a method for controlling a radar level gauge system, the radar level gauge system comprising: a communication module configured to be connected to an external communication device; a measurement module configured to generate, send and receive measurement signals; a control connection configured to connect the communication module to the measurement module, the control connection being configured to be in a high impedance mode at least during measurement by the measurement module; a power supply configured to provide power to the measurement module; an energy storage device coupled to the power supply; a measurement connection connecting the communication module to the energy storage device, wherein the energy storage device is arranged and configured to be charged through the measurement connection and to provide power to the power supply device to perform measurement by the measurement module; and a switch arranged between the communication module and the energy storage device. The method comprises: receiving a command to perform measurement in the measurement module; controlling the switch to be in an open circuit mode to disconnect the measurement connection between the communication module and the energy storage device; performing measurement by the measurement module; and controlling the switch to be in a closed mode to reconnect the measurement connection between the communication module and the energy storage device.

[0028] By means of the described method, the described radar level gauge system can be controlled to perform measurements with a significantly reduced risk of interference with the measurement.

[0029] Additional effects and features of the second aspect of the present invention are largely similar to those described above in conjunction with the first aspect of the present invention.

[0030] Further features and advantages of the present invention will become apparent when studying the appended claims and the following description.Those skilled in the art realize that different features of the present invention can be combined to create embodiments other than those described below, without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] These and other aspects of the present invention will now be described in more detail with reference to the accompanying drawings, which show example embodiments of the present invention, in which:

[0032] Figure 1 A field device in the form of a radar level gauge installed in an example tank is schematically shown;

[0033] Figure 2 is a block diagram schematically showing an exemplary embodiment of a field device according to the invention in the form of a radar level gauge system;

[0034] Figure 3 is a block diagram schematically illustrating an exemplary embodiment of a radar level gauge system; and

[0035] Figure 4 is a flow chart outlining the steps of a method for controlling a radar level gauge system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] In this detailed description, exemplary embodiments of field devices according to the present invention are discussed with reference to guided wave radar level gauge systems connected via a two-wire current loop connection. It should be noted that this is not intended to limit the scope of the present invention, and the present invention is equally applicable to other field devices, such as non-contact radar level gauge systems, temperature sensors, pressure sensors, etc. In addition, the two-wire current loop can be configured to work according to various communication standards (e.g., 4mA-20mA, HART, Foundation Fieldbus, Profibus, etc.).

[0037] Figure 1 A field device in the form of a radar level gauge 1 is schematically shown installed in an example tank 2. The radar level gauge 1 is connected to a remote host / master device 3 via a two-wire current loop 4, which is also used to provide power to the radar level gauge 1. The tank 2 contains a product 6, and the radar level gauge 1 determines, in operation, a filling level L of the product 6 in the tank 2 based on an electromagnetic transmission signal propagating towards a surface 7 of the product 6 and an electromagnetic reflection signal resulting from reflection of the transmission signal at the surface 7.

[0038] After the filling level L as an example of a process variable has been determined, the radar level meter transmits a measurement signal S indicating the filling level L via the two-wire current loop 4 . L Provided to the remote host / master device 3. Figure 2 and Figure 3 The radar level gauge and the process of performing measurements by the radar level gauge are described in more detail.

[0039] Figure 2 2 is a block diagram schematically showing a radar level gauge system 200 according to an embodiment of the present invention. The radar level gauge system 200 includes a communication module 202 configured to connect to an external communication device (e.g., Figure 1 The connection may be made via a fieldbus interface 203 for connecting the radar level gauge system 200 to a two-wire 4mA to 20mA connection.

[0040] The radar level gauge system 200 further comprises a measurement module 204 configured to generate, send and receive measurement signals; a control connection 206 configured to connect the communication module 202 to the measurement module 204, wherein the control connection is configured to be in a high impedance mode at least during measurement by the measurement module 204; a power supply 208 configured to provide power to the measurement module 204; an energy storage 210 coupled to the power supply 208; and a measurement connection 212 connecting the communication module 202 to the energy storage 210, wherein the energy storage 210 is arranged to be charged via the measurement connection 212 and configured to provide power to the power supply 208 for measurement to be performed by the measurement module 204.

[0041] Furthermore, the radar level gauge system 200 comprises a switch 214 arranged between the communication module 202 and the energy storage 210 , which switch 214 can be controlled to disconnect a measurement connection 212 between the communication module 202 and the energy storage 210 during a measurement by the measuring module 204 .

[0042] Here, the control connection 206 and the measurement connection 212 refer to physical wired connections that facilitate the communicative coupling between the control module 202 and the measurement module 204 .

[0043] Here, although the energy storage 210 is shown as a capacitor arranged between the switch 214 and the power supply 208, the energy storage 210 may also be arranged at a different position as long as the electrical coupling between the communication module 202 and the energy storage 210 can be disconnected by the switch 214. Figure 2 As shown, the switch is a double switch 214 that disconnects the two conductors required to provide energy to the energy storage 210 .

[0044] Furthermore, for example, the energy storage 210 may be an integrated part of the power supply 208. The energy storage 210 may also be provided in the form of a rechargeable battery.

[0045] In addition, both the energy storage 210 and / or the power supply 208 may be integrated into the measurement module 204 along with the required measurement circuitry. For illustrative purposes, the energy storage 210, the power supply 208, and the measurement module 204 are shown as separate components. For example, the power supply 208 may be a linear regulator or a DC / DC converter disposed on the same circuit board as the measurement circuitry.

[0046] The measurement connection 112 is adapted such that power losses in the connection are low, thereby facilitating efficient charging of the power storage 210. However, for some applications and in particular in explosion-sensitive environments, it may be desirable to adapt the resistance of the communication module 202 in order to provide suitable current and voltage levels to the measurement connection 112. The resistance of the measurement connection 112 between the communication module 202 and the energy storage 210 should be as low as possible and may preferably be below 100Ω.

[0047] The control connection 206 may be configured to be controllably between a low impedance mode and a high impedance mode. In the high impedance mode, the control connection 206 preferably has an impedance above 10 kΩ, and in the low impedance mode, the control connection 206 preferably has an impedance below 100 Ω. Preferably, there is at least a tenfold impedance difference between the low impedance mode and the high impedance mode.

[0048] Figure 3 2 is a block diagram schematically showing a radar level gauge system 200, which further comprises a second switch 302 arranged to disconnect the control connection 206 between the communication module 202 and the measurement module 204. By controlling the switch 302, the control connection can be set in a low impedance mode (switch closed) or in a high impedance mode (switch open). Figure 3 The switch 302 is shown as a physical switch, and the function of switching between the high impedance mode and the low impedance mode may also be provided in the communication module 202 and / or the measurement module 204 through, for example, a tri-state buffer or a general purpose I / O (GPIO) interface.

[0049] Figure 4 The present invention is an overview of a method for controlling Figure 2 and Figure 3 Flow chart of the steps of a method for a radar level gauge system of the present invention. The method comprises: receiving a command to perform a measurement in the measurement module 202 400; controlling the switch 214 to be in an open mode to disconnect the measurement connection 212 between the communication module 202 and the power supply 210 402; performing a measurement by the measurement module 204 404; and controlling the switch 214 to be in a closed mode to reconnect the measurement connection 212 between the communication module 202 and the energy storage 210 406.

[0050] For example, the command to perform the measurement may be sent by the communication module 202 to the measurement module 204 based on a set frequency for intermittent measurement or based on a request from the remote host 3. The measurement module 204 receives the command to perform the measurement, and may also include an implementation in which the measurement is performed intermittently based on a predetermined frequency or in which the measurement is performed once the energy storage is full. In such an implementation, the command can thus be regarded as a trigger for initiating the measurement.

[0051] An exemplary measurement sequence may include: the communication module 202 issues a command to switch on the power of the measurement module 204, which is preferably suspended or placed in a low power mode when no measurement is performed, in order to reduce the overall energy consumption of the radar level gauge system 200. Once the measurement is completed, the measurement module 204 may report back to the communication module 202. The switch 214 may thereby be controlled by the measurement module or by the communication module so that the switch is closed when the measurement is completed and when the energy storage device needs to be charged.

[0052] However, the order of the steps of the method may be modified. For example, the step 402 of controlling the switch to be in open circuit mode may be performed before the measurement module receives the command 400 to perform a measurement.

[0053] exist Figure 3 In the illustrated embodiment, a second switch 302 including a control connection 206 between the brake communication module 202 and the measurement module 204 is included, and the second switch 302 can be controlled by the measurement module 204. The switch 302 can also be controlled based on an estimated or known time for performing a measurement, such that the communication module 202 can control the second switch 302 to close when a predetermined time has passed.

[0054] According to an example embodiment, the measurement module 204 may monitor the state of the energy storage 210 and control the switch 214 based on the state of charge of the energy storage 210. Thus, when it is determined that the energy storage 210 needs to be recharged, the switch may be closed. For example, if the state of charge of the energy storage 210 is below a predetermined threshold, the switch 214 may be controlled to be closed. The switch 214 may also be controlled based on an estimated time required to fully charge the energy storage. In one embodiment, based on a known characteristic of an input signal received by the communication module 202, the switch may be controlled to remain closed for a period of time, which is known to be sufficient to fully or sufficiently charge the energy storage. The time for charging the energy storage may also be determined based on a known current and voltage provided to the energy storage from the communication module 202, or based on a known quantity and a lookup table or predetermined equation for determining the characteristics of the energy storage 210.

[0055] Although the invention has been described with reference to specific exemplary embodiments thereof, many different changes, modifications, etc. will become apparent to those skilled in the art. In addition, it should be noted that parts of the system and method may be omitted, interchanged or arranged in various ways, while the system and method are still capable of performing the functions of the invention.

[0056] In addition, various variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, based on a study of the drawings, the present disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. A radar level meter system, comprising: a communication module configured to connect to an external communication device; a measurement module configured to generate, send and receive measurement signals; a control connection configured to connect the communication module to the measurement module, the control connection configured to be in a high impedance mode at least during measurements by the measurement module; a power supply configured to provide power to the measurement module; an energy storage device coupled to the power source; a measurement connection connecting the communication module to the energy storage, wherein the energy storage is arranged to be charged via the measurement connection and is configured to provide power to the power supply for performing measurements by the measurement module; as well as A switch is arranged between the communication module and the energy storage device and can be controlled to disconnect a measurement connection between the communication module and the energy storage device during a measurement by the measurement module.

2. The system according to claim 1, wherein: The measurement connection is a connection having an impedance which is suitable for providing power from the communication module to the energy store.

3. The system according to claim 1, wherein: The control connection is configured to enable control between a low impedance mode and a high impedance mode.

4. The system according to claim 1, wherein: The high impedance mode of the control connection is adapted to have a sufficiently high impedance to prevent conducted disturbances from propagating via the control connection to the measurement module.

5. The system according to claim 3, wherein: The impedance of the control connection in the high impedance mode is at least 10 times the impedance of the control connection in the low impedance mode.

6. The system according to claim 3, wherein: The communication module is configured to control the control connection to operate in a high impedance mode or a low impedance mode.

7. The system according to claim 1, wherein: The control connection is an optical connection.

8. The system according to claim 1, wherein: The switch is also configured to be controlled by the measurement module to disconnect the communication module from the power supply during measurement by the measurement module.

9. The system according to claim 1, wherein: The switch is a semiconductor switch.

10. The system according to claim 1, wherein: The switch is an electromechanical relay.

11. The system of claim 1, further comprising a second switch arranged to disconnect a control connection between the communication module and the measurement module.

12. The system of claim 1, wherein: The measuring module is configured to be placed in a low power mode during charging of the energy storage.

13. The system of claim 1, wherein: The communication module is configured to connect to a 4 mA to 20 mA current loop interface.

14. A method for controlling a radar level gauge system, the radar level gauge system comprising: a communication module configured to connect to an external communication device; a measurement module configured to generate, send and receive measurement signals; a control connection configured to connect the communication module to the measurement module, the control connection configured to be in a high impedance mode at least during measurements by the measurement module; a power supply configured to provide power to the measurement module; an energy storage device coupled to the power source; a measurement connection connecting the communication module to the energy storage, wherein the energy storage is arranged and configured to be charged via the measurement connection and to provide power to the power supply for performing measurements by the measurement module; and a switch, arranged between the communication module and the energy storage; Wherein, the method comprises: receiving, in the measurement module, a command to perform measurement; controlling the switch to be in an open circuit mode to disconnect a measurement connection between the communication module and the energy storage; The measurement module performs measurement; and The switch is controlled in a closed mode to reconnect the measurement connection between the communication module and the energy storage.

15. The method according to claim 14, wherein: The switch is controlled by the measuring module.

16. The method according to claim 14, further comprising: The control connection is controlled to be in a low impedance mode when the switch is in a closed mode, and the control connection is controlled to be in a high impedance mode when the switch is in an open mode.

17. The method according to claim 14, further comprising: The state of the energy storage device is monitored by the measuring module, and the switch is controlled based on the state of charge of the energy storage device.

18. The method according to claim 14, further comprising: The switch is controlled based on an estimated time required to fully charge the energy storage.

19. The method according to claim 14, further comprising: The measuring module is controlled to operate in a low power mode during charging of the energy storage.

Images