State monitoring system

Abstract

To provide a state monitoring device to which sensors of various output specifications can be connected.SOLUTION: A state monitoring device 1 includes at least an input circuit of a signal from a sensor. A sensor input circuit 11 includes: a power-supply terminal PW, a signal-input terminal SIG, and a reference terminal COM; a comparator circuit U having a first node (+) connected to the signal-input terminal SIG and a second node (-) to which reference voltage is applied; and a first switching element SW1 and a first current-limiting element R1 connected in series between the power-supply terminal PW and the signal-input terminal SIG.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] A condition monitoring system that monitors the operating state of industrial machinery to detect malfunctions and other problems at an early stage is equipped with an input circuit that receives signals from various sensors that detect the rotational speed, etc., of the equipment being monitored. For example, Japanese Patent No. 2730112 (Patent Document 1) discloses a circuit that receives signals from a DC two-wire sensor such as a proximity switch, photoelectric switch, or ultrasonic switch. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 2730112 Summary of the Invention [Problem to be solved by the invention]

[0004] In the configuration disclosed in Japanese Patent No. 2730112 (Patent Document 1), the input circuit is specialized for signals from DC two-wire sensors, and cannot input other types of signals, such as DC three-wire sensor signals or voltage pulse signals.

[0005] Condition monitoring devices are subject to restrictions on how they collect the information required for condition monitoring depending on the structure and configuration of the monitored object. Specifically, this includes the fact that only certain sensors can be installed on the monitored object, or that sensors with the same functions but different output specifications may already be installed on the monitored object.

[0006] Because the types of rotation signals that can be input to the condition monitoring device are limited, in the former case, it is not possible to install a sensor that corresponds to the input circuit of the condition monitoring device, making it impossible to measure the rotation signal, and in the latter case, it is not possible to use signals from existing sensors, so adding additional sensors requires additional costs.

[0007] The present disclosure aims to provide a condition monitoring device that solves the above-mentioned problems and that can connect sensors with a variety of output specifications. [Means for solving the problem]

[0008] The present disclosure relates to a condition monitoring device including at least an input circuit for a signal from a sensor, the input circuit including a power supply terminal, a signal input terminal, and a reference terminal, a comparison circuit having a first input node connected to the signal input terminal and a second input node to which a reference voltage is applied, and a first switch element and a first current limiting element connected in series between the power supply terminal and the signal input terminal. [Effects of the Invention]

[0009] According to the condition monitoring device of the present disclosure, sensor output signals of various output specifications can be input without replacing the input circuit. [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 sensor input circuit 11 included in the state monitoring device 1. FIG. [Figure 3] FIG. 1 is a diagram for explaining the connection state between a sensor input circuit and a DC three-wire sensor (load built-in type). [Figure 4] FIG. 1 is a diagram for explaining the connection state between a sensor input circuit and a DC three-wire sensor (load-free type). [Figure 5] 3 is a diagram for explaining a connection state between a sensor input circuit and a DC two-wire sensor. FIG. [Figure 6] 6 is an operational waveform diagram for explaining the operation of the sensor input circuit when the DC three-wire or DC two-wire sensor shown in FIGS. 3 to 5 is connected. FIG. [Figure 7] FIG. 2 is a diagram for explaining a connection state between a sensor input circuit and a pulse output type sensor. [Figure 8] 10 is an operational waveform diagram for explaining the operation of the sensor input circuit when a pulse output type sensor is connected. FIG. [Figure 9] FIG. 2 is a diagram for explaining the connection state between a sensor input circuit and a PNP type DC three-wire sensor. [Figure 10] FIG. 10 is an operational waveform diagram for explaining the operation of the sensor input circuit when a PNP type DC three-wire sensor is connected. [Figure 11] FIG. 10 is a diagram showing the configuration of a sensor input circuit with an expanded input voltage range. 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. Industrial machine 2 includes a rotation sensor 21 and other sensors 22.

[0013] The rotation sensor 21 detects a signal for measuring the rotation speed of the monitored object. For example, signals from various sensors installed in the monitored object, signals from a control device of the monitored object, etc. are transmitted as rotation signals from the industrial machine 2 to the condition monitoring device 1.

[0014] The other sensors 22 are sensors for monitoring the state of the object to be monitored, and are sensors for detecting acceleration, temperature, displacement, pressure, and the like.

[0015] The condition monitoring device 1 includes a sensor input circuit 11, a sensor input circuit 12, and a processing circuit 13.

[0016] The sensor input circuit 11 receives a signal from the rotation sensor 21 and converts it into a format that can be processed by the processing circuit 13 (for example, a predetermined voltage pulse signal).

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

[0018] The processing circuit 13 processes the signals or data from the sensor input circuits 11 and 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] Generally, there are four main types of rotation sensors, each with a different output signal format. These types include, for example, DC 3-wire sensors (load built-in), DC 3-wire sensors (NPN or PNP transistor output), DC 2-wire sensors, and voltage pulse output sensors. In the past, in order to receive output signals of different formats, a dedicated input circuit corresponding to each format was required. It was not usually possible for an input circuit for signals of a different format to receive and process signals of other types.

[0022] The sensor input circuit 11 built into the condition monitoring device 1 of this embodiment can accommodate input signals in a number of formats, so there is no need to prepare a large number of variations of condition monitoring devices.

[0023] Fig. 2 is a diagram showing the configuration of the sensor input circuit 11 included in the condition monitoring device 1. The sensor input circuit 11 shown in Fig. 2 has three input terminals. That is, the sensor input circuit 11 includes a power supply terminal PW, a signal input terminal SIG, and a reference terminal COM.

[0024] The power supply terminal PW and the reference terminal COM are connected to a power supply PS1 that supplies a power supply voltage VDC for the sensor. Although the power supply PS1 is included in the sensor input circuit 11 in Fig. 2, a voltage source for the sensor (not shown) may be connected between the power supply terminal PW and the reference terminal COM from outside the sensor input circuit 11.

[0025] The sensor input circuit 11 further includes a comparison circuit U, a switch element SW1, and a current limiting element R1. The signal input terminal SIG is connected to the + input node of the comparison circuit U. The switch element SW1 and the current limiting element R1, which is a load resistor, are connected in series between the power supply terminal PW and the signal input terminal SIG.

[0026] The comparator circuit U has two or more input nodes, one or more output nodes, and positive and negative power supply nodes. Of the input nodes of the comparator circuit U, the signal input terminal SIG is connected to the + input node, and a reference voltage Vth is applied to the - input node. VCC, which is the drive power supply for the comparator circuit U, is connected to the positive and negative power supply nodes of the comparator circuit U. Note that, although the power supply PS2 that generates the reference voltage Vth is included in the sensor input circuit 11 in FIG. 2, a reference voltage generated by a reference voltage source for the sensor (not shown) external to the sensor input circuit 11 may also be connected to the - input node of the comparator circuit U.

[0027] The output node of the comparison circuit U is the output of the sensor input circuit 11 and is connected to the processing circuit 13. For example, the processing circuit 13 includes a counter that counts the rotation signal from the rotation sensor 21.

[0028] The switch element SW1 is an element that switches between open and short circuits, and is a mechanical switch or an electronic switch such as a MOSFET, a photocoupler, etc. The switch element SW1 may also be a jumper wire, a fuse, etc.

[0029] The current limiting element R1 is an element that limits the current, and is either an ohmic element such as a load resistor or a non-ohmic element such as a constant current diode.

[0030] The comparison circuit U is an element that compares the voltages of two inputs and outputs the comparison result, and may be a comparator, an operational amplifier, or the like.

[0031] The power supply PS2 that supplies the reference voltage Vth is a variable voltage source, and can use a DC-DC converter, a voltage divider circuit, a D / A (digital / analog) converter, etc. The reference voltage Vth is a threshold voltage that the comparator circuit U uses to judge the input signal.

[0032] The drive power supply voltage VCC of the comparison circuit U is supplied from a power supply PS3. Although the power supply PS3 is shown inside the sensor input circuit 11, the drive power supply voltage VCC may be supplied from outside the sensor input circuit 11. The output signal COUT of the comparison circuit U becomes the output signal of the sensor input circuit 11.

[0033] The polarities in the circuit diagram are merely an example, and the polarities of the corresponding positive and negative terminals may be independently reversed.

[0034] The following describes how the components of the sensor input circuit 11 function according to the type of input signal.

[0035] Fig. 3 is a diagram illustrating the connection state between a sensor input circuit and a DC three-wire sensor (load built-in type). In Fig. 3, a rotation sensor 21A is connected to the sensor input circuit 11. The rotation sensor 21A is a DC three-wire sensor with a load built-in type, and includes a sensor main circuit MC, a switch element TrN, and a load R21.

[0036] When connecting the rotation sensor 21A, which is a DC three-wire sensor with a built-in load, to the sensor input circuit 11, the power supply terminal PT of the sensor is connected to the power supply terminal PW, the signal terminal ST of the sensor is connected to the signal input terminal SIG, and the reference terminal CT of the sensor is connected to the reference terminal COM. Then, the switch element SW1 is opened to prevent current from flowing through the current limiting element R1.

[0037] Furthermore, the reference voltage Vth is set to any voltage within the range between the power supply voltage VDC and the ground voltage, and more preferably to a voltage intermediate between the power supply voltage VDC and the ground voltage.

[0038] By setting the switch element SW1 in this way and connecting the rotation sensor 21A to the sensor input circuit 11, the power supply voltage VDC is supplied to the sensor, and the signal (voltage) input from the signal input terminal SIG is compared with the reference voltage Vth by the comparison circuit U and converted into a pulse signal that can be input to the processing circuit 13.

[0039] Fig. 4 is a diagram illustrating the connection state between a sensor input circuit and a DC three-wire sensor (load-free type). In Fig. 4, a rotation sensor 21B is connected to the sensor input circuit 11. The rotation sensor 21B is a DC three-wire sensor with no built-in load, and includes a sensor main circuit MC and a switch element TrN. Unlike Fig. 3, the load R21 is not included in the rotation sensor 21B.

[0040] When connecting the rotation sensor 21B to the sensor input circuit 11, as in Figure 3, the sensor's power supply terminal PT is connected to the power supply terminal PW, the sensor's signal terminal ST is connected to the signal input terminal SIG, and the sensor's reference terminal CT is connected to the reference terminal COM. Then, the switch element SW1 is shorted. Furthermore, the reference voltage Vth is set to any voltage within the range from the power supply voltage VDC to the voltage obtained by adding the residual voltage to the ground voltage. Generally, it is desirable to set the reference voltage Vth to a voltage midway between the power supply voltage VDC and the ground voltage.

[0041] 4, by setting the switch element SW1, the power supply voltage VDC is supplied to the rotation sensor 21B, and the power supply voltage VDC is applied to the signal input terminal SIG via the current limiting element R1, and the output state of the switch element TrN of the rotation sensor 21B is converted into a voltage. That is, the short-circuit / open state between the signal terminal ST and the reference terminal CT is converted into a low-level / high-level voltage, respectively.

[0042] The converted voltage is then compared with a reference voltage Vth by a comparator circuit U, and is further converted into a pulse signal that can be input to the processing circuit 13 of FIG.

[0043] 5 is a diagram for explaining the connection state between the sensor input circuit and the DC two-wire sensor. When connecting the DC two-wire rotation sensor 21C to the sensor input circuit 11, the signal terminal ST of the sensor is connected to the signal input terminal SIG, the reference terminal CT of the sensor is connected to the reference terminal COM, and the switch element SW1 is short-circuited. Nothing is connected to the power supply terminal PW (it is left open).

[0044] Furthermore, the reference voltage Vth is set to any voltage within the range from the power supply voltage VDC to the voltage obtained by adding the residual voltage to the ground voltage. In general, it is desirable to set the reference voltage Vth to a voltage intermediate between the power supply voltage VDC and the ground voltage.

[0045] By doing as described above, power is supplied to the rotation sensor 21C via the current limiting element R1 and the signal input terminal SIG and signal terminal ST. Then, depending on the output state (impedance change) of the switch element TrN of the rotation sensor 21C, the voltage division ratio with the current limiting element R1 changes, causing the voltage at the signal input terminal SIG to change. This changed voltage is compared with the reference voltage Vth by the comparator circuit U and further converted into a pulse signal that can be input to the processing circuit 13.

[0046] Figure 6 is an operational waveform diagram illustrating the operation of the sensor input circuit when the DC three-wire or DC two-wire sensor shown in Figures 3 to 5 is connected. As shown in Figure 6, the switch element TrN of the rotation sensor alternates between open and closed states depending on the output of the sensor main circuit MC. The voltage at the signal input terminal SIG is approximately 0 V when the switch element TrN is closed, and approximately the power supply voltage VDC when the switch element TrN is open. This voltage is compared with the reference voltage Vth, and the result is the output signal COUT.

[0047] That is, when the switch element TrN is in a closed state, the voltage of the output signal COUT is 0 V. On the other hand, when the switch element TrN is in an open state, the voltage of the output signal COUT is the power supply voltage VCC.

[0048] FIG. 7 is a diagram illustrating the connection state between a sensor input circuit and a pulse output sensor. The rotation sensor 21D includes a sensor main circuit MC and a pulse output circuit. The pulse output circuit outputs a voltage pulse signal having a high level and a low level to the signal terminal ST, based on the voltage of the reference terminal CT. The pulse output circuit may be, for example, a circuit including two push-pull transistors. Although not shown, a separate power supply voltage may be supplied to the pulse output circuit. When connecting the rotation sensor 21D to the sensor input circuit 11, the signal terminal ST of the sensor is connected to the signal input terminal SIG, the reference terminal CT of the sensor is connected to the reference terminal COM, and the switch element SW1 is set to open. Nothing is connected to the power supply terminal PW (open).

[0049] Furthermore, the reference voltage Vth is set to any voltage between the upper and lower limits of the voltage pulse signal, and is generally preferably set to a voltage midway between the upper and lower limits.

[0050] In this way, the pulse voltage input to the signal input terminal SIG is compared with the reference voltage Vth in the comparator circuit U and is further converted into a pulse signal that can be input to the processing circuit 13.

[0051] FIG. 8 is an operational waveform diagram for explaining the operation of the sensor input circuit when a pulse output type sensor is connected.

[0052] As shown in Figure 8, the rotation sensor's pulse output circuit alternates between high and low states depending on the output of the sensor's main circuit MC. The voltage at the signal input terminal SIG is low when the pulse output is low, and high when the pulse output is high. This voltage is compared with the reference voltage Vth, and the result is the output signal COUT.

[0053] That is, when the pulse output signal is in a low level state, the voltage of the output signal COUT is 0 V. On the other hand, when the pulse output signal is in a high level state, the voltage of the output signal COUT is the power supply voltage VCC.

[0054] As described above, by providing the condition monitoring device 1 with the sensor input circuit 11 of this embodiment, even if the output of the rotation sensor 21 installed in the industrial machine 2 can take several different forms, it is possible to use the same circuit to handle these by changing the settings of the sensor input circuit 11.

[0055] [Embodiment 2] In the first embodiment, an NPN transistor is mainly used in the output section of the rotation sensor 21 connected to the condition monitoring device 1. However, a PNP transistor may also be used. In the second embodiment, a sensor input circuit will be described that can accommodate cases where the sensor output transistor is an NPN transistor as well as a PNP transistor output.

[0056] 9 is a diagram for explaining the connection state between a sensor input circuit and a PNP-type DC three-wire sensor. In the second embodiment, a sensor input circuit 11A is used as the input circuit of the condition monitoring device 1 instead of the sensor input circuit 11 in FIG.

[0057] Sensor input circuit 11A shown in Fig. 9 includes a second switch element SW2 and a second current limiting element R2 in addition to the configuration of sensor input circuit 11 shown in Fig. 2. The configuration of other parts of sensor input circuit 11A is similar to that of sensor input circuit 11 shown in Fig. 2, and therefore description thereof will not be repeated here. Rotation sensor 21E includes a sensor main circuit MC, an output switch element TrP, a power supply terminal PT, a signal terminal ST, and a reference terminal CT.

[0058] As shown in the configuration in FIG. 9, by adding a switch element SW2 and a current limiting element R2 in series between the reference terminal COM and the signal input terminal SIG, it becomes possible to input the output signal of a PNP-type DC three-wire sensor or a current signal (4-20 mA, etc.).

[0059] In sensor input circuit 11A, if the type of input signal is a PNP-type DC three-wire sensor or a current signal, switch SW1 is opened and switch element SW2 is shorted, and in other cases switch element SW2 is opened. If switch element SW2 is opened, the circuit becomes equivalent to the circuit shown in Figure 2, so the description of the operation in this case will not be repeated.

[0060] Fig. 10 is an operational waveform diagram for explaining the operation of the sensor input circuit when a PNP type DC three-wire sensor is connected. With reference to Fig. 9 and Fig. 10, we will explain how the circuit works when a PNP type DC three-wire sensor and a current signal are connected.

[0061] When connecting rotation sensor 21E, a PNP-type DC three-wire sensor, to sensor input circuit 11A, power supply terminal PT of rotation sensor 21E is connected to power supply terminal PW, signal terminal ST of rotation sensor 21E is connected to signal input terminal SIG, and reference terminal CT of rotation sensor 21E is connected to reference terminal COM. Then, switch element SW1 is opened, and switch element SW2 is short-circuited.

[0062] Furthermore, the reference voltage Vth is set to any voltage within the range of the voltage obtained by subtracting the residual voltage from the power supply voltage VDC to the ground voltage. In general, it is desirable to set the reference voltage Vth to a voltage midway between the power supply voltage VDC and the ground voltage.

[0063] In this way, the power supply voltage VDC is supplied to the rotation sensor 21E. Furthermore, the voltage at the signal input terminal SIG changes depending on the state of the sensor's switch element TrP. That is, when the switch element TrP is in a conductive state, the switch element TrP raises the signal input terminal SIG to the power supply voltage VDC. On the other hand, when the switch element TrP is in a non-conductive state, the current limiting element R2 lowers the signal input terminal SIG to near the ground voltage.

[0064] The voltage of the signal input terminal SIG that fluctuates in this way is compared with a reference voltage Vth in the comparator circuit U, and is further converted into a pulse signal that can be input to the processing circuit 13.

[0065] When connecting a current signal to the sensor input circuit 11A, the signal line for the current signal from the sensor is connected to the signal input terminal SIG, the sensor's ground line is connected to the reference terminal COM, switch element SW1 is open, and SW2 is shorted. Nothing is connected to the power supply terminal PW. Furthermore, the reference voltage Vth is set to any voltage within the range of the maximum and minimum current values ​​of the current signal multiplied by the resistance of the current limiting element R2. Generally, it is desirable to set the reference voltage Vth to a voltage obtained by multiplying the intermediate current value by the resistance of the current limiting element R2.

[0066] With this connection, a current signal flows between the signal input terminal SIG and the reference terminal COM via the current limiting element R2, and the current signal is converted into a voltage at the signal input terminal SIG. This converted voltage is compared with the reference voltage Vth by the comparator circuit U, and is further converted into a pulse signal that can be input to the processing circuit 13.

[0067] Furthermore, by insulating the primary and secondary sides of the comparison circuit U, it becomes possible to connect it in series with a device that acquires the same current signal.

[0068] [Embodiment 3] FIG. 11 is a diagram showing the configuration of a sensor input circuit with an expanded input voltage range. In the third embodiment, a sensor input circuit 11B is used as the input circuit of the condition monitoring device 1 instead of the sensor input circuit 11 of FIG. 1. The sensor input circuit 11B shown in FIG. 11 further includes resistive elements R3 and R4 in addition to the configuration of the sensor input circuit 11 shown in FIG. 2. The resistive element R3 is inserted between the signal input terminal SIG and the + input node of the comparator circuit U. The resistive element R4 is connected between the + input node of the comparator circuit U and the reference terminal COM.

[0069] The configuration of other parts of sensor input circuit 11B is similar to that of sensor input circuit 11 shown in FIG. 2, and therefore description thereof will not be repeated here.

[0070] As shown in the circuit diagram of FIG. 11, by adding resistive elements R3 and R4 as voltage dividing resistors, it becomes possible to accept an input signal with a larger amplitude than the signal amplitude allowed for the output signal COUT.

[0071] In other words, a normal comparator circuit U cannot input a signal that exceeds the range of the power supply voltage VCC. For this reason, the voltage between the signal input terminal SIG and the reference terminal COM must generally be equal to or less than the power supply voltage VCC.

[0072] On the other hand, by adding voltage dividing resistors (R3, R4), the voltage of the signal input to the comparison circuit U can be reduced by a factor of (R4 / (R3+R4)), allowing rotation signals with a wider voltage range to be input.

[0073] As described above, the status monitoring device using the sensor input circuit of any of the first to third embodiments can use a rotation measurement method suited to the measurement target by increasing the number of types of rotation signals that can be input. As a result, it is possible to expand the range of targets whose rotations can be measured and reduce the cost of rotation measurement.

[0074] The sensor input circuits of the first to third embodiments may be applied to the sensor input circuit 12 of Fig. 1 that receives input from a sensor other than a rotation sensor. In this case as well, various sensors with different signal output formats can be connected.

[0075] [Note] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0076] (Item 1) The present disclosure relates to a condition monitoring device 1 including at least an input circuit for a signal from a sensor. The sensor input circuit 11 shown in Fig. 2 includes a power supply terminal PW, a signal input terminal SIG, and a reference terminal COM, a comparison circuit U having a first input node (+) connected to the signal input terminal SIG and a second input node (-) to which a reference voltage is applied, and a first switch element SW1 and a first current limiting element R1 connected in series between the power supply terminal PW and the signal input terminal SIG.

[0077] (Item 2) In the condition monitoring device 1 described in item 1, the sensor input circuit 11 further includes, as shown in FIG. 2, a first power supply PS1 that supplies a first power supply voltage VDC between the power supply terminal PW and the reference terminal COM, and a reference power supply PS2 that supplies a reference voltage Vth between the reference terminal COM and the second input node (-).

[0078] (Item 3) In the status monitoring device according to item 2, the reference power supply PS2 is a variable voltage source including a DC-DC converter, a D / A converter, or a voltage divider circuit.

[0079] (4) In the condition monitoring device described in 1, the first switch element SW1 is either a mechanical switch, an electronic switch, a jumper, or a fuse configured to be able to switch between opening and closing a current path connecting the power supply terminal PW and the signal input terminal SIG via the first current limiting element R1, and the first current limiting element R1 is an ohmic element or a non-ohmic element.

[0080] (Item 5) In the condition monitoring device described in item 1, as shown in FIG. 1, the sensor is a rotation sensor 21 that monitors the rotation of the industrial machine 2 that is the object of condition monitoring, and further includes a processing circuit 13 that receives the output of the comparison circuit U and detects the rotation speed of the object of condition monitoring.

[0081] (Item 6) In the condition monitoring device described in item 1, as shown in FIG. 9, the sensor input circuit 11A further includes a second switch element SW2 and a second current limiting element R2 connected in series between the reference terminal COM and the signal input terminal SIG.

[0082] (Item 7) In the condition monitoring device described in item 1, as shown in FIG. 11, the sensor input circuit 11B further includes a first resistor element R3 and a second resistor element R4, the first input node (+) is connected to the signal input terminal SIG via the first resistor element R3, the second resistor element R4 is connected between the first input node (+) and the reference terminal COM, and a voltage obtained by dividing the voltage of the signal input terminal SIG by the first resistor element R3 and the second resistor element R4 is applied to the first input node (+).

[0083] 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]

[0084] 1 Condition monitoring device, 2 Industrial machine, 3 Server, 11, 11A, 11B, 12 Sensor input circuit, 13 Processing circuit, 21, 21A, 21B, 21C, 21D, 21E Rotation sensor, 22 Sensor, COM, CT Reference terminal, MC Sensor main circuit, PS1, PS2, PS3 Power supply, PW Power supply terminal, R1, R2 Current limiting element, R3, R4 Resistive element, R21 Load resistor, SIG Signal input terminal, ST Signal terminal, SW1, SW2 Switch element, TrN, TrP Transistor, U Comparison circuit.

Claims

1. A condition monitoring device including at least an input circuit for a signal from a sensor, The input circuit a power supply terminal, a signal input terminal, and a reference terminal; a comparison circuit having a first input node connected to the signal input terminal and a second input node to which a reference voltage is applied; The condition monitoring device includes a first switch element and a first current limiting element connected in series between the power supply terminal and the signal input terminal.

2. The input circuit a first power supply that supplies a first power supply voltage between the power supply terminal and the reference terminal; The condition monitoring device according to claim 1 , further comprising: a reference power supply that supplies the reference voltage between the reference terminal and the second input node.

3. 3. The condition monitoring device according to claim 2, wherein the reference power supply is a variable voltage source including a DC-DC converter, a D / A converter, or a voltage divider circuit.

4. the first switch element is any one of a mechanical switch, an electronic switch, a jumper, and a fuse configured to be able to switch between opening and closing a current path connecting the power supply terminal and the signal input terminal via the first current limiting element, The condition monitoring device of claim 1 , wherein the first current limiting element is an ohmic element or a non-ohmic element.

5. the sensor is a rotation sensor that monitors the rotation of the object to be monitored; The condition monitoring device according to claim 1 , further comprising a processing circuit that receives an output from the comparison circuit and detects a rotation speed of the object to be monitored.

6. The input circuit 2. The condition monitoring device according to claim 1, further comprising a second switch element and a second current limiting element connected in series between the reference terminal and the signal input terminal.

7. the input circuit further includes a first resistor element and a second resistor element; the first input node is connected to the signal input terminal via the first resistor element; the second resistive element is connected between the first input node and the reference terminal; 2. The status monitoring device according to claim 1, wherein a voltage obtained by dividing a voltage at said signal input terminal by said first resistor element and said second resistor element is applied to said first input node.

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