State monitoring device

Abstract

To provide a state monitoring device which can be used even if a polarity of an input signal is inverse and reduces the time and effort for an adjustment of an input voltage range.SOLUTION: A digital input circuit 12 comprises: an insulation element U1 in which digital signals are received by input node pairs P1 and P2 and output signals including signal components of the digital signals are outputted from output node pairs P3 and P4 electrically insulated from the input node pairs P1 and P2; and a current limit circuit 100 which is connected to one of the input node pairs P1 and P2 and limits currents passing the input node pairs P1 and P2. The insulation element U1 is configured in such a manner that the input node pairs P1 and P2 have no polarity. The current limit circuit 100 includes a first current limit element CRD1 and a second current limit element CRD2, which are non-ohmic, connected in series and in mutually reverse directions.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a condition monitoring device for industrial machinery. [Background technology]

[0002] A condition monitoring device that monitors the operating state of industrial machinery to detect malfunctions at an early stage receives signals from various sensors that detect the rotational speed of the equipment being monitored, and is equipped with an input circuit for communicating by digital signals with the industrial machinery control device, external operation device, etc. For example, Japanese Patent Laid-Open Publication No. 2008-312093 (Patent Document 1) discloses a configuration that uses a photocoupler and a current-limiting resistor in the digital input circuit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-312093 Summary of the Invention [Problem to be solved by the invention]

[0004] In digital communication, to protect both communicating devices, the input and output of the communication path are isolated by an isolation element such as a photocoupler. To drive this isolation element, a current limiting element may be provided in the input circuit.

[0005] In the technology described in JP 2008-312093 A (Patent Document 1), an input signal is current-limited by an ohmic current-limiting resistor and then input to an isolation element. Because the current-limiting resistor is ohmic, the limited current depends on the input voltage. To drive an isolation element, the current must be within a range compatible with the element, so the voltage range of the input signal is limited. Because the input voltage range is limited, it is necessary to check whether the input signal is within that range, and if it is not within that range, the input voltage must be adjusted, which is a time-consuming process.

[0006] In particular, with condition monitoring devices, the structure and configuration of the object being monitored, i.e., the characteristics of the digital signal such as voltage and current, may be unknown, making investigation and adjustments more time-consuming.

[0007] The present disclosure aims to provide a condition monitoring device that solves the above-mentioned problems, that can be used even when the polarity of the input signal is reversed, and that reduces the effort required to adjust the input voltage range. [Means for solving the problem]

[0008] The present disclosure relates to a condition monitoring device including at least an input circuit for receiving a digital signal. The input circuit includes an isolation element that receives the digital signal at a pair of input nodes and outputs an output signal including a signal component of the digital signal from a pair of output nodes electrically isolated from the pair of input nodes, and a current limiting circuit that is connected to one of the pair of input nodes and limits the current passing through the pair of input nodes. The isolation element is configured so that the pair of input nodes are non-polar, and the current limiting circuit includes first and second non-ohmic current limiting elements connected in series and in opposite directions to each other. [Effects of the Invention]

[0009] According to the condition monitoring device of the present disclosure, input signals with a wide range of positive and negative voltages can be input, so that the input signals can be input to the input circuit with almost no need to check the characteristics of the input signals, such as voltage and polarity. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a diagram showing the configuration and connection relationship of a status monitoring device and peripheral devices. [Figure 2] 2 is a diagram showing the configuration of a digital input circuit 12 included in the status monitoring device 1. FIG. [Figure 3] FIG. 10 is a diagram for explaining the characteristics of a constant current diode. [Figure 4] 3 is an operational waveform diagram for explaining the operation of the digital input circuit shown in FIG. 2. FIG. [Figure 5] FIG. 10 is a diagram illustrating a modified example of a digital input circuit. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0012] [Embodiment 1] Fig. 1 shows the configuration and connection relationship of a condition monitoring device and peripheral devices. In Fig. 1, industrial machine 2 is the equipment to be monitored, and corresponds to equipment including a rotating body such as a generator or an electric motor, such as wind power generation equipment.

[0013] The status monitoring device 1 monitors the industrial machine 2. The status monitoring device 1 is connected to the industrial machine 2, an external operation device 4, and a server 3.

[0014] The industrial machine 2 includes a sensor 21 and a control device 22. The sensor 21 is a sensor for monitoring the state of an object to be monitored, and is a sensor for detecting acceleration, rotational speed, temperature, displacement, pressure, etc. The control device 22 is a device that controls and monitors the object to be monitored. The control device 22 outputs, for example, a signal that notifies the operating state of the industrial machine 2 (operating / stopped, etc.) and a signal that indicates a measurement execution command.

[0015] The external operation device 4 outputs signals such as measurement execution, reset, and operation mode change signals to the state monitoring device 1 from a person or device managing the industrial machine 2.

[0016] The condition monitoring device 1 includes a sensor input circuit 11, a digital input circuit 12, and a processing circuit 13.

[0017] The sensor input circuit 11 receives signals from the sensor 21 and converts them into a format that can be processed by the processing circuit 13 (such as a digital value after A / D (analog / digital) conversion, a specified voltage signal, etc.). For example, the sensor input circuit 11 may include a preamplifier, a power supply circuit, an analog front end, an A / D converter, a decoder / encoder, etc. The digital input circuit 12 receives digital signals transmitted from the control device 22 and the external operation device 4.

[0018] The processing circuit 13 processes the signals or data from the sensor input circuit 11 and the digital input circuit 12, and performs one or more of diagnosis, storage, display, and transfer to a higher-level system.

[0019] The server 3 is an example of a host system of the condition monitoring device 1. Instead of the server 3, the condition monitoring device 1 may transmit an output signal to a display or provide feedback to the industrial machine 2 to be monitored.

[0020] The condition monitoring device 1 may also include other elements such as a recording unit for storing measurement data, setting values, processing variables, etc., a communication unit for acquiring data other than that from the sensor, and a console unit for changing setting values, etc. from outside.

[0021] Fig. 2 is a diagram showing the configuration of the digital input circuit 12 included in the status monitoring device 1. The digital input circuit 12 shown in Fig. 2 includes an isolation element U1 and a current limiting circuit 100. A digital input signal is applied between input terminals IN1 and IN2. In addition, a digital output signal is applied from the digital input circuit 12 to the processing circuit 13 in Fig. 1 as conduction / non-conduction between terminals COUTP and COUTN.

[0022] The isolation element U1 receives a digital signal at a pair of input nodes P1 and P2, and outputs an output signal containing a signal component of the digital signal from a pair of output nodes P3 and P4 electrically isolated from the pair of input nodes P1 and P2. The isolation element U1 also includes a current limiting circuit 100 connected to one of the pair of input nodes P1 and P2 and limiting the current passing through the pair of input nodes P1 and P2.

[0023] The isolation element U1 is configured so that the pair of input nodes P1 and P2 has no polarity. More specifically, as shown in FIG. 2, the isolation element U1 is a photocoupler including a first light-emitting diode D11 and a second light-emitting diode D12 connected in anti-parallel between the pair of input nodes P1 and P2. When the voltage at input terminal IN2 becomes higher than the voltage at input terminal IN1, the light-emitting diode D11 emits light, causing the transistor TrN to become conductive. Conversely, when the voltage at input terminal IN1 becomes higher than the voltage at input terminal IN2, the light-emitting diode D12 emits light, causing the transistor TrN to become conductive. This allows the photocoupler to transmit signals even if the polarity of the signal lines connected to input terminals IN1 and IN2 is reversed.

[0024] As the isolation element U1, other than a photocoupler, a small signal transformer (pulse transformer), some capacitive coupling, inductive coupling, or GMR isolator may be used.

[0025] The current limiting circuit 100 includes a first non-ohmic current limiting element CRD1 and a second non-ohmic current limiting element CRD2 connected in series and in reverse direction. Specifically, constant current diodes can be used as the first current limiting element CRD1 and the second current limiting element CRD2. In the example of Fig. 2, the cathode of the first current limiting element CRD1 is connected to the terminal IN1, the anode of the first current limiting element CRD1 is connected to the anode of the second current limiting element CRD2, and the cathode of the second current limiting element CRD2 is connected to the input node P1 of the isolation element U1.

[0026] Figure 3 is a diagram illustrating the characteristics of a constant current diode. As shown in Figure 3, when the voltage V>0 (anode voltage > cathode voltage) is in the range of Vmin to Vmax, the constant current diode has the characteristic of passing a constant pinch-off current Ip. In the range of V<0 (anode voltage > cathode voltage), the diode passes current with a low resistance but does not limit the current.

[0027] In addition to constant current diodes, semiconductor elements including a circuit that utilizes constant current operation in the saturation region of a MOSFET, a current mirror circuit, etc. may also be used as the first current limiting element CRD1 and the second current limiting element CRD2.

[0028] FIG. 4 is an operational waveform diagram for explaining the operation of the digital input circuit shown in FIG. 2. FIG. 4 shows the signal SIG input to the input terminal pair and the corresponding state of the output transistor TrN. The High / Low indicated on the signal SIG indicates the voltage or current value of the High / Low level of the digital signal. When the level of the signal SIG exceeds the ON threshold VtON, the state of the output transistor TrN becomes closed, and when the level of the signal SIG falls below the OFF threshold VtOFF, the state of the output transistor TrN becomes open. Note that when the level of the signal SIG is between the ON threshold VtON and the OFF threshold VtOFF, the state of the output transistor TrN becomes indefinite.

[0029] To widen the voltage range of the input signal, one method is to use a non-ohmic current limiting element so that the limiting current does not depend on the voltage of the input signal. However, non-ohmic current limiting elements, such as current regulator diodes, are polarized, so the input signal is limited to direct current and positive voltage. Therefore, it is still necessary to check the polarity of the input signal.

[0030] In the condition monitoring device 1 of this embodiment, a non-polar element is used for the isolation element U1 in the digital input circuit 12, or polarized elements are connected in parallel in reverse to make the input node pair non-polar. Furthermore, non-ohmic current limiting elements CRD1 and CRD2 are connected in series in reverse to allow input signals over a wide voltage range to be input regardless of polarity (non-ohmic current limiting elements allow current to flow in the reverse direction as described in FIG. 3).

[0031] This allows input signals with a wide range of positive and negative voltages to be input, so that the input signal can be input to the input circuit with almost no need to check its characteristics, such as voltage or polarity.

[0032] That is, according to the condition monitoring device of the first embodiment, the digital input circuit uses an isolation element U1 configured so that the input node pair P1, P2 has no polarity, and a current limiting circuit 100 configured to limit current in both directions. With this configuration, there is no need to worry about the polarity of the signal input to the input terminals IN1, IN2, and the effort required to adjust the input voltage is reduced.

[0033] [Embodiment 2] In the configuration shown in the first embodiment, one of the current limiting elements CRD1 and CRD2 is always connected in reverse polarity. Generally, when a non-ohmic current limiting element is connected in reverse polarity, it operates like a rectifying element and allows current to flow. However, compared to a typical rectifying element, the current limiting elements CRD1 and CRD2 have inferior element characteristics, such as temperature characteristics, forward voltage, and characteristic variations. For example, there are problems such as the ON threshold voltage VtON varying depending on the individual element and temperature, the ON voltage being high, and operation not being guaranteed due to variations.

[0034] The condition monitoring device of the second embodiment includes a digital input circuit 12A which is a modification of the digital input circuit 12 shown in the first embodiment. Fig. 5 is a diagram showing a modification of the digital input circuit.

[0035] The digital input circuit 12A shown in Fig. 5 includes a current limiting circuit 100A and an isolation element U1. The isolation element U1 has the same configuration as that described in Fig. 2, and therefore description thereof will not be repeated here.

[0036] The current limiting circuit 100A includes a first rectifying element D1 and a second rectifying element D2 in addition to a first non-ohmic current limiting element CRD1 and a second non-ohmic current limiting element CRD2 connected in series and in an opposite direction to each other.

[0037] The first rectifier D1 is connected in parallel with the first current limiting element CRD1 and selectively passes a current having a polarity opposite to that of the first current limiting element CRD1. The second rectifier D2 is connected in parallel with the second current limiting element CRD2 and selectively passes a current having a polarity opposite to that of the second current limiting element CRD2.

[0038] Schottky barrier diodes can be used as the first rectifier element D1 and the second rectifier element D2. It is desirable to use elements with a low forward voltage, such as Schottky barrier diodes, as the rectifier elements D1 and D2, as this can reduce the reverse current flowing through the current limiting element.

[0039] In addition to Schottky barrier diodes, normal pn junction diodes or ideal diodes IC may be used as the rectifying elements D1 and D2.

[0040] As described above, in the second embodiment, as in the first embodiment, the non-ohmic current limiting element limits the current to a range appropriate for driving the insulating element over a wide voltage range. Furthermore, by connecting two non-ohmic polarity current limiting elements in series in opposite directions, the polarity of the input signal can be used without regard to the polarity of the input signal. Furthermore, since signals can be input regardless of the voltage or polarity of the input signal, the effort required to check and adjust the characteristics of the input signal is reduced.

[0041] Furthermore, in the second embodiment, the rectifying elements D1 and D2 are connected in parallel in the reverse direction to the current limiting elements CRD1 and CRD2, respectively, as shown in Fig. 5. This allows the reverse current flowing through the current limiting elements to be bypassed by the rectifying elements, stabilizing the characteristics of the current limiting elements when they are connected in reverse and preventing problems with operational variations.

[0042] [Note] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0043] (Item 1) The present disclosure relates to a condition monitoring device 1 including at least a digital input circuit 12 that receives a digital signal. As shown in FIG. 2, the digital input circuit 12 includes an isolation element U1 that receives the digital signal at a pair of input nodes P1 and P2 and outputs an output signal containing a signal component of the digital signal from a pair of output nodes P3 and P4 that are electrically isolated from the pair of input nodes P1 and P2, and a current limiting circuit 100 that is connected to one of the pair of input nodes P1 and P2 and limits the current passing through the pair of input nodes P1 and P2. The isolation element U1 is configured so that the pair of input nodes P1 and P2 are non-polar. The current limiting circuit 100 includes a first non-ohmic current limiting element CRD1 and a second non-ohmic current limiting element CRD2 that are connected in series and in reverse directions.

[0044] (Item 2) In the condition monitoring device 1 described in item 1, as shown in FIG. 5, the current limiting circuit 100A further includes a first rectifying element D1 connected in parallel with the first current limiting element CRD1 and selectively passing a current having an opposite polarity to that of the first current limiting element CRD1, and a second rectifying element D2 connected in parallel with the second current limiting element CRD2 and selectively passing a current having an opposite polarity to that of the second current limiting element CRD2.

[0045] (Item 3) In the state monitoring device 1 described in item 2, the first rectifying element D1 and the second rectifying element D2 are Schottky barrier diodes.

[0046] (Item 4) In the state monitoring device 1 described in item 1 or 2, the first current limiting element CRD1 and the second current limiting element CRD2 are constant current diodes.

[0047] (Item 5) In the condition monitoring device described in item 1 or 2, as shown in FIG. 2 or 5, the isolation element U1 is a photocoupler including a first light-emitting diode D11 and a second light-emitting diode D12 connected in anti-parallel to each other between the pair of input nodes P1 and P2.

[0048] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0049] 1 condition monitoring device, 2 industrial machine, 3 server, 4 external operation device, 11 sensor input circuit, 12, 12A digital input circuit, 13 processing circuit, 21 sensor, 22 control device, 100, 100A current limiting circuit, CRD1, CRD2 current limiting elements, D1, D2 rectifier elements, D11, D12 light-emitting diodes, IN1, IN2 input terminals, P1, P2 input node pair, P3, P4 output node pair, TrN output transistor, U1 isolation element.

Claims

1. A condition monitoring device comprising at least an input circuit for receiving a digital signal, The input circuit an isolation element that receives the digital signal at a pair of input nodes and outputs an output signal including a signal component of the digital signal from a pair of output nodes electrically isolated from the pair of input nodes; a current limiting circuit connected to one of the pair of input nodes to limit a current passing through the pair of input nodes; the isolation element is configured so that the input node pair is non-polarized; The condition monitoring device, wherein the current limiting circuit includes first and second non-ohmic current limiting elements connected in series and in reverse direction to each other.

2. The current limiting circuit a first rectifying element connected in parallel with the first current limiting element and selectively passing a current having a polarity opposite to that of the first current limiting element; The condition monitoring device according to claim 1 , further comprising a second rectifying element connected in parallel with the second current limiting element and selectively passing a current having a polarity opposite to that of the second current limiting element.

3. The condition monitoring device according to claim 2 , wherein the first rectifying element and the second rectifying element are Schottky barrier diodes.

4. 3. The condition monitoring device according to claim 1, wherein the first current limiting element and the second current limiting element are constant current diodes.

5. 3. The condition monitoring device according to claim 1, wherein the isolation element is a photocoupler including a first light-emitting diode and a second light-emitting diode connected in anti-parallel to each other between the pair of input nodes.

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