Analog input module and control system

Abstract

To provide an analog input module capable of detecting input values of a plurality of kinds of analog signals, and a control system.SOLUTION: The present application relates to an analog input module having a plurality of channels for detecting an analog signal input from a control target. Each of the plurality of channels has a detection circuit for detecting an analog signal input to the input terminal as a voltage signal. The input value of the analog signal is calculated based on the voltage signal detected by the detection circuit. The circuit configuration of the detection circuit can be switched based on a setting signal received from the arithmetic device.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an analog input module and a control system. [Background technology]

[0002] There are known control systems that control plant facilities, such as power plants, which are composed of a large number of components. In this type of control system, the controlled object is controlled based on control signals generated by arithmetic processing using input values ​​of various analog signals detected from the controlled object. For example, Patent Document 1 discloses a control system that includes an analog input module for detecting input values ​​of analog signals input from the controlled object, and performs arithmetic processing to control the controlled object using the input values ​​of the analog signals detected by the analog input module. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-146033 [Patent Document 2] Japanese Patent Application Publication No. 63-141103 Summary of the Invention [Problem to be solved by the invention]

[0004] The analog input module provided in the control system shown in Patent Document 1 is designed to have a circuit configuration for detecting analog signals input from the controlled object. Therefore, if the type of analog signal to be detected is changed, it is difficult to respond, and it becomes necessary to redesign and develop the analog input module, including changing the design of the circuit configuration.

[0005] At least one embodiment of the present disclosure has been made in consideration of the above circumstances, and has an object to provide an analog input module and a control system capable of detecting input values ​​of multiple types of analog signals. [Means for solving the problem]

[0006] In order to solve the above problem, an analog input module according to at least one embodiment of the present disclosure comprises: An analog input module having a plurality of channels for detecting an analog signal input from a controlled object, Each of the plurality of channels comprises: an input terminal to which the analog signal can be input; a detection circuit for detecting the analog signal input to the input terminal as a voltage signal; an input value calculation unit for calculating an input value of the analog signal based on the voltage signal detected by the detection circuit; a circuit switching unit for switching the circuit configuration of the detection circuit based on the type of the analog signal; Equipped with The circuit switching unit switches the circuit configuration based on a setting signal received from a calculation device that performs calculation processing using the input values ​​calculated by the input value calculation units of the plurality of channels.

[0007] In order to solve the above problem, a control system according to at least one embodiment of the present disclosure includes: an analog input module according to at least one embodiment of the present disclosure; a computing device for performing the computational processing; Equipped with. [Effects of the Invention]

[0008] According to at least one embodiment of the present disclosure, it is possible to provide an analog input module and a control system capable of detecting input values ​​of multiple types of analog signals. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating an overall configuration of a control system according to an embodiment. [Figure 2] FIG. 2 is a diagram showing the internal configuration of the analog input module of FIG. 1. [Figure 3] 3 is a diagram showing the circuit configuration of the detection circuit of FIG. 2 together with the peripheral configuration when an analog current is input as an analog signal. [Figure 4] 3 is a diagram showing the circuit configuration of the detection circuit of FIG. 2 together with the peripheral configuration when an analog voltage is input as an analog signal. [Figure 5] 3 is a diagram showing the circuit configuration of the detection circuit of FIG. 2 together with the peripheral configuration when an analog voltage from a thermocouple element is input as an analog signal. [Figure 6] This is a modification of FIG. [Figure 7] 3 is a diagram showing an example of the circuit configuration of the detection circuit of FIG. 2 together with the peripheral configuration when an analog voltage from a resistance temperature detector is input as an analog signal. [Figure 8] 10 is a diagram showing another example of the circuit configuration of the detection circuit of FIG. 2 together with the peripheral configuration when an analog voltage from a resistance temperature detector is input as an analog signal. [Figure 9] 10 is a diagram showing another example of the circuit configuration of the detection circuit of FIG. 2 together with the peripheral configuration when an analog voltage from a resistance temperature detector is input as an analog signal. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. However, the configurations described as the embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention.

[0011] First, the overall configuration of a control system 1 including an analog input module according to at least one embodiment of the present disclosure will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing the overall configuration of a control system 1 according to one embodiment.

[0012] The control system 1 is a distributed control system (DCS) for controlling a control target 3, such as a plant facility. The control system 1 acquires input signals Si from instruments such as sensors included in the control target 3, performs various arithmetic processing using the acquired input signals Si, and transmits output signals So, which are control signals based on the arithmetic results, to the control target 3, thereby controlling the control target 3.

[0013] The control system 1 includes an input / output module 2, an MPS 4, an EMS 6, an OPC 8, and an ACS 10. These components communicate with each other via a communication network 12, and thereby cooperate to control the control target 3. Each of these components of the control system 1 is configured by an electronic computing device such as a computer including, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), etc.

[0014] The input / output module 2 is an interface device for inputting and outputting an input signal Si and an output signal So between the control target 3 and the MPS 4. The input / output module 2 is capable of inputting and outputting the input signal Si and the output signal So, which include analog or digital signals, and Fig. 1 shows, as some components of the input / output module 2, an analog input module 14 that can input an analog signal Sa from the control target 3 as the input signal Si, and an input / output adapter 16 that communicates various data (input signal Si or output signal So) input and output via the input / output module 2 with the MPS 4.

[0015] The specific configuration of the analog input module 14 will be described later, but the input / output module 2 includes at least one analog input module 14 depending on the type of analog signal Sa included in the input signal Si. While Fig. 1 illustrates an example in which the input / output module 2 includes multiple analog input modules 14, the number of analog input modules 14 included in the input / output module 2 is not limited.

[0016] Although not shown in Figure 1, the input / output module 2 may also include, in addition to the aforementioned analog input module 14, at least one of a digital input module for inputting a digital signal contained in the input signal Si from the controlled object 3, an analog output module for outputting an analog signal contained in the output signal So to the controlled object 3, or a digital output module for outputting a digital signal contained in the output signal So to the controlled object 3.

[0017] The MPS 4 is a control device for automatically controlling the controlled object 3 and for carrying out various related arithmetic processing. Specifically, the MPS 4 performs various arithmetic processing based on predetermined control logic using an input signal Si acquired from an instrument or the like included in the controlled object 3 via the input / output module 2, thereby generating an output signal So that is output to the controlled object 3 as a control signal.

[0018] The EMS 6 is a maintenance terminal with an engineering function for system construction and maintenance management in the control system 1. The EMS 6 can perform maintenance so that automatic control is properly performed by the control system 1 through the construction of the control logic performed by the MPS 4 and the setting of various parameters used in the control logic.

[0019] The OPS 8 is a terminal that allows an operator to monitor and operate the control system 1. The OPS 8 includes a monitoring device such as a display that allows the operator to check the operating status of the control system, and an operation terminal that allows the operator to operate the control system 1.

[0020] The ACS 10 is a terminal for collecting various data handled by the control system 1 and creating reports based on the collected data.

[0021] Next, a description will be given of the internal configuration of the analog input module 14 provided in the input / output module 2. Fig. 2 is a diagram showing the internal configuration of the analog input module 14 of Fig. 1.

[0022] The analog input module 14 includes an input connector 17 , a detection circuit 18 , and an MCU (microcontroller unit) 20 .

[0023] The input connector 17 has an input terminal 24 to which an analog signal Sa from the controlled object 3 can be input. In this embodiment, particularly, the input connector 17 has a plurality of input terminals 24 corresponding to a plurality of channels CH1, CH2, ... Each input terminal 24 includes a pair of a positive input terminal 24a and a negative input terminal 24b to which the positive side and the negative side of the analog signal Sa can be input, respectively, and is connected to the input side of the corresponding detection circuit 18.

[0024] The detection circuit 18 is configured to detect the analog signal Sa input to the input terminal 24, and has a circuit configuration for detecting the analog signal Sa input to the input terminal 24 as a voltage signal. The circuit configuration of the detection circuit 18 is configured as an electric circuit including circuit elements for converting the analog signal Sa into a voltage signal for detection, and is configured to be switchable depending on the type of the analog signal Sa.

[0025] In the analog input module 14, such a detection circuit 18 is provided for each input terminal 24 of the input connector 17. That is, the multiple detection circuits 18 can detect multiple analog signals Sa input from the controlled object 3 for each channel CH1, CH2, ... of the input connector 17. Since these multiple detection circuits 18 have the same circuit configuration, the following description will representatively describe one specific detection circuit 18.

[0026] The MCU 20 is a microcontroller unit (MCU) mounted on the analog input module 14, and includes, as its functional configuration, an input value calculation unit 26 for calculating the input value of the analog signal Sa based on the voltage signal detected by the detection circuit 18 in the analog input module 14, and a circuit switching unit 28 for switching the circuit configuration of the detection circuit 18 depending on the type of the analog signal Sa.

[0027] 2, the input value calculation unit 26 includes an A / D converter for converting the voltage signal detected by the detection circuit 18 into a digital signal, and an amplifier circuit for amplifying the voltage signal detected by the detection circuit 18 when the voltage signal is weak. The input module 14 also includes a DC / DC power supply 32 for supplying power to the input connector 17 and the isolated power supply 30 connected to the MCU 20, an SPI communication isolation unit 34 for performing communication with the MPS 4, including sending and receiving various data, and an FPGA 36 which is a host control unit of the MCU 20.

[0028] The circuit switching unit 28 is configured to switch the circuit configuration of the detection circuit 18 based on the type of analog signal Sa. The circuit switching unit 28 switches the circuit configuration of the detection circuit 18 based on a setting signal Ss received from the MPS 4, which is a higher-level control device for the analog input module 14. Specifically, the setting signal Ss from the MPS 4 is first acquired by the FPGA 36, which then generates a control signal for switching the detection circuit 18 in accordance with the setting signal Ss. This control signal is transmitted from the FPGA 36 via the SPI communication insulating unit 34 to the circuit switching unit 28 included in the MCU 20, thereby switching the circuit configuration of the detection circuit 18. In this way, in the analog input module 14, the circuit configuration of the detection circuit 18 is switched based on the type of analog signal Sa input to the input terminal 24 of the input connector 17, making it possible to detect input values ​​of different types of analog signals Sa using a common module configuration.

[0029] Next, we will specifically explain the switching control of the circuit configuration of the detection circuit 18 included in the analog input module 14 for each type of analog signal Sa. First, we will explain the circuit configuration of the detection circuit 18 when an analog current Ia is input as the analog signal Sa, with reference to Fig. 3. Fig. 3 is a diagram showing the circuit configuration of the detection circuit 18 of Fig. 2 together with the peripheral configuration when an analog current Ia is input as the analog signal Sa.

[0030] In the circuit configuration shown in Fig. 3, an analog current Ia measured by a measuring device included in the controlled object 3 is input as an analog signal Sa to a detection circuit 18 via input terminals 24 (positive input terminal 24a and negative input terminal 24b). For ease of illustration, the input connector 17 shown in Fig. 2 is omitted in Fig. 3.

[0031] In this case, the circuit switching unit 28 (see FIG. 2) switches the circuit configuration of the detection circuit 18 to a circuit configuration for acquiring the input value of the analog current Ia, based on the setting signal Ss from the MPS 4. Specifically, the circuit switching unit 28 switches the switches SW1 and SW4 to the ON state and switches SW2, SW3, and SW5 to the OFF state, thereby switching the circuit configuration of the detection circuit 18 so that the analog current Ia input from the input terminal 24 flows through the first resistor R1, which is a current detection resistor, and the potential difference V1 across the first resistor R1 is input as a voltage signal to the voltage detection terminals V+ and V− of the MCU 20. The MCU 20 determines the potential difference V1 across the first resistor R1 based on the voltage signal input to the voltage detection terminals V+ and V−, and the input value calculation unit 26 calculates the input value of the analog current Ia using the following equation. Ia=V1 / R1 (1)

[0032] Here, if the analog current Ia input to the detection circuit 18 is very small, the potential difference V1 across the first resistor R1 will also be very small, which may reduce the detection accuracy of the MCU 20. For this reason, in the circuit configuration of Fig. 3, a bias current Ib is output to the first resistor R1 from a bias voltage output terminal IB of the MCU 20. In this way, if the analog current Ia input to the detection circuit 18 is very small, the bias current Ib may be supplied to the first resistor R1 to increase the potential difference V1 across the first resistor R1, thereby improving the detection accuracy of the potential difference V1 by the MCU 20.

[0033] In this way, when the analog signal Sa input to the analog input module 14 is an analog current Ia, the input value of the analog current Ia can be suitably detected in the analog input module 14 by switching the circuit configuration of the detection circuit 18 as shown in Figure 3.

[0034] Next, the circuit configuration of the detection circuit 18 in Fig. 2 when an analog voltage Va is input as the analog signal Sa will be described with reference to Fig. 4. Fig. 4 is a diagram showing the circuit configuration of the detection circuit 18 in Fig. 2 together with the peripheral configuration when an analog voltage Va is input as the analog signal Sa.

[0035] In the embodiment shown in Fig. 4, an analog voltage Va measured by a measuring device included in the controlled object 3 is input as an analog signal Sa to the detection circuit 18 via the input terminals 24 (positive input terminal 24a and negative input terminal 24b). In Fig. 4, the input connector 17 shown in Fig. 1 is omitted for clarity.

[0036] In this case, the circuit switching unit 28 (see FIG. 2) switches the circuit configuration of the detection circuit 18 to a circuit configuration for acquiring the input value of the analog voltage Va, based on the setting signal Ss from the MPS 4. Specifically, the circuit switching unit 28 switches the switches SW2 and SW4 to the ON state and switches SW1, SW3, and SW5 to the OFF state, thereby switching the circuit configuration of the detection circuit 18 so that the analog voltage Va input to the detection circuit 18 is applied to a voltage-dividing circuit 38 including a second resistor R2 and a third resistor R3. A potential difference V2 across the second resistor R2 of the voltage-dividing circuit 38 is input to the voltage detection terminals V+ and V− of the MCU 20. The MCU 20 determines the potential difference V2 across the second resistor R2 based on the voltage signals input to the voltage detection terminals V+ and V−, and the input value calculation unit 26 calculates the input value of the analog voltage Va using the following equation: Va=V2×(R3+R2) / R2 (2)

[0037] In this way, when the analog signal Sa input to the analog input module 14 is the analog voltage Va, the input value of the analog voltage Va can be suitably detected in the analog input module 14 by switching the circuit configuration of the detection circuit 18 as shown in Fig. 4. In particular, by dividing the analog voltage Va using the voltage divider circuit 38 to generate a voltage signal to be detected by the MCU 20, the analog voltage Va can be suitably detected even when the analog voltage Va exceeds the range that can be detected by the MCU 20.

[0038] Next, the circuit configuration of the detection circuit 18 in Fig. 2 when an analog voltage Va from the thermocouple element 3a included in the controlled object 3 is input as the analog signal Sa will be described with reference to Fig. 5. Fig. 5 is a diagram showing the circuit configuration of the detection circuit 18 in Fig. 2 together with the peripheral configuration when an analog voltage Va from the thermocouple element 3a is input as the analog signal Sa.

[0039] 5, an analog voltage Va from a thermocouple element 3a included in a controlled object 3 is input as an analog signal Sa to a detection circuit 18 via input terminals 24 (positive input terminal 24a and negative input terminal 24b). For ease of illustration, the input connector 17 shown in FIG. 1 is omitted in FIG. 5.

[0040] In this case, the circuit switching unit 28 switches the circuit configuration of the detection circuit 18 to a circuit configuration for acquiring the input value of the analog voltage Va from the thermocouple element 3a, based on the setting signal Ss from the MPS 4. Specifically, the circuit switching unit 28 switches the switch SW3 to the on state and the switches SW1, SW2, SW4, and SW5 to the off state, thereby switching the circuit configuration of the detection circuit 18 so that the analog voltage Va input from the input terminal 24 is input as a voltage signal to the voltage detection terminals V+ and V- of the MCU 20. The MCU 20 detects the input value of the analog voltage Va based on the voltage signal input to the voltage detection terminals V+ and V-.

[0041] The input value calculation unit 26 may calculate the temperature measurement value based on the thus detected analog voltage Va. In this case, a table showing the relationship between the analog voltage Va and the temperature measurement value is stored in advance in a storage means such as a memory, and the analog voltage Va detected by the MCU 20 can be compared with the table to calculate the temperature detection value.

[0042] Here, the analog voltage Va from the thermocouple element 3a is generally very small, so that the detection circuit 18 directly inputs the analog voltage Va to the voltage detection terminals V+, V- of the MCU 20 without dividing it using the voltage divider circuit 38 as in the embodiment described above with reference to Fig. 4. Furthermore, if the analog voltage Va input to the voltage detection terminals V+, V- of the MCU 20 is very small and falls below an allowable range, the analog voltage Va may be amplified by an amplifier circuit (not shown) built into the MCU 20. In this case, the input value calculation unit 26 may calculate the temperature detection value by previously storing a table in a storage means such as a memory, which indicates the relationship between the amplified analog voltage Va and the temperature detection value.

[0043] Furthermore, in this circuit configuration, if a break occurs in the wiring 40 connecting the input terminal 24 and the thermocouple element 3a, a dark current Id1 is supplied from the dark current output terminal ID1 to the positive input terminal 24a so that the temperature measurement value calculated by the input value calculation unit 26 is fixed to the high temperature side (i.e., so that a burn-up operation occurs in the event of a break). Specifically, a sixth resistor R6 is disposed on the path through which the dark current Id1 flows, and if a break occurs in the wiring 40, a predetermined voltage (a voltage obtained by pulling up the power supply voltage of the MCU 20 by the sixth resistor R6) is applied to the positive input terminal 24a. As a result, if a break occurs in the wiring 40, the temperature measurement value calculated by the input value calculation unit 26 is fixed to the high temperature side, thereby making it possible to preferably prevent the control state from becoming unstable.

[0044] FIG. 6 is a modified example of FIG. 5. In the modified example shown in FIG. 6, similar to FIG. 5, the circuit configuration of the detection circuit 18 allows for suitable detection of the analog voltage Va from the thermocouple element 3a. However, if a break occurs in the wiring 40 connecting the input terminal 24 and the thermocouple element 3a, a dark current Id2 is supplied from the dark current output terminal ID2 to the negative input terminal 24b so that the temperature measurement value calculated by the input value calculation unit 26 is fixed to the low temperature side (i.e., so that a burn-down operation occurs in the event of a break). Specifically, a seventh resistor R7 is disposed on the path through which the dark current Id2 flows. If a break occurs in the wiring 40, a predetermined voltage (a voltage obtained by pulling up the power supply voltage of the MCU 20 by the seventh resistor R7) is applied to the negative input terminal 24b. As a result, if a break occurs in the wiring 40, the temperature measurement value calculated by the input value calculation unit 26 is fixed to the low temperature side, thereby preventing the control state from becoming unstable.

[0045] Next, the circuit configuration of the detection circuit 18 of Fig. 2 when the analog voltage Va from the resistance temperature detector 3b included in the controlled object 3 is input as the analog signal Sa will be described with reference to Fig. 7. Fig. 7 is a diagram showing an example of the circuit configuration of the detection circuit 18 of Fig. 2 together with the peripheral configuration when the analog voltage Va from the resistance temperature detector 3b is input as the analog signal Sa.

[0046] In the embodiment shown in Fig. 7, an analog voltage Va from a resistance temperature detector 3b included in a controlled object 3 is input as an analog signal Sa to a detection circuit 18 via input terminals 24 (positive input terminal 24a and negative input terminal 24b). In Fig. 7, the input connector 17 shown in Fig. 1 is omitted for clarity. Note that this resistance temperature detector 3b may be used, for example, for measuring the ambient temperature for cold junction compensation of the temperature detection value of the thermocouple element 3a shown in Figs. 5 and 6.

[0047] In this case, the circuit switching unit 28 (see FIG. 2) switches the circuit configuration of the detection circuit 18 based on the setting signal Ss from the MPS 4 to a circuit configuration that applies a predetermined sense current Is1 to the resistance temperature detector 3b and detects a potential difference V4 across the resistance temperature detector 3b as a voltage signal. Specifically, the circuit switching unit 28 switches the switches SW3 and SW4 to the ON state and switches SW1, SW2, and SW5 to the OFF state, thereby switching the circuit configuration of the detection circuit 18 so that the sense current Is1 is applied to the resistance temperature detector 3b from the sense current output terminal IS1 and the potential difference V4 across the resistance temperature detector 3b is input to the voltage detection terminals V+ and V− of the MCU 20. The input value calculation unit 26 of the MCU 20 calculates the actual value of the sense current Is1 based on the potential difference (sense current measurement voltage Vs) between the voltage detection terminal V− and ground potential and the fourth resistor R4 using the following equation: Is1=Vs / R4 (3-1) Then, the input value calculation unit 26 uses the potential difference V4 input to the voltage detection terminals V+, V− and the above equation (3-1) to calculate the resistance value RTD of the resistance temperature detector 3b according to the following equation. RTD=V4 / Is1 (3-2)

[0048] The input value calculation unit 26 also stores a table showing the relationship between the resistance value RTD of the resistance temperature detector 3b and the measured temperature in a storage device such as a memory in advance, and calculates the measured temperature of the resistance temperature detector 3b by comparing the actual measured resistance value RTD calculated using the above formula with the table. The measured temperature of the resistance temperature detector 3b calculated in this manner can be used as an ambient temperature value for cold junction compensation of the thermocouple element 3a, as described above. By switching the circuit configuration of the detection circuit 18 as in this embodiment, the analog input module 14 can preferably obtain the measured temperature value of the resistance temperature detector 3b using the so-called two-wire method.

[0049] Next, Fig. 8 is a diagram showing another example of the circuit configuration of the detection circuit 18 of Fig. 2 together with the peripheral configuration when an analog voltage Va from the resistance temperature detector 3b is input as the analog signal Sa. In the configuration example shown in Fig. 8, two channels (a first channel CH1 and a second channel CH2) of the input connector 17 are connected to the resistance temperature detector 3b in a four-wire system, and a predetermined wiring resistance r exists in each of the wires between the input connector 17 and the resistance temperature detector 3b. In this case, the MCU 20 of the first channel CH1 and the MCU 20 of the second channel CH2 cooperate with each other to detect the temperature measurement value of the resistance temperature detector 3b.

[0050] In this circuit configuration, the circuit configuration of the detection circuit 18A corresponding to the first channel CH1 is switched so as to apply a sense current Is2 from the sense current output terminal IS2 to the resistance temperature detector 3b and measure the actual measurement value of the sense current Is2. Specifically, in the detection circuit 18A, the switch SW4 is switched to the ON state and the switches SW1, SW2, SW3, and SW5 are switched to the OFF state, so that the sense current Is2 is supplied from the sense current output terminal IS2 to the resistance temperature detector 3b. The input value calculation unit 26 calculates the actual measurement value of the sense current Is2 using the voltage value (sense current measurement voltage Vs) input to the voltage detection terminal V- and the fourth resistor R4 using the following equation: Is2=Vs / R4 (4-1)

[0051] The circuit configuration of the detection circuit 18B corresponding to the second channel CH2 is switched so as to detect the potential difference V5 across the resistance temperature detector 3b as a voltage signal. Specifically, the circuit switching unit 28 switches the switches SW3 and SW4 to the ON state and switches SW1, SW2, and SW5 to the OFF state so that the potential difference V5 across the resistance temperature detector 3b is input to the voltage detection terminals V+ and V- of the MCU 20.

[0052] As described above, the sense current Is2 detected in the first channel CH1 and the potential difference V5 detected in the second channel CH2 are shared by the MCUs 20 of the first channel CH1 and the second channel CH2 via the FPGA 36 (see Figure 2), and the resistance value RTD of the resistance temperature detector 3b is calculated by the following equation in the input value calculation unit 26 in at least one of the MCUs 20. RTD=V5 / Is2 (4-2)

[0053] Furthermore, the input value calculation unit 26 in at least one of the MCUs 20 stores a table showing the relationship between the resistance value RTD of the resistance temperature detector 3b and the measured temperature in a storage means such as a memory in advance, and can calculate the measured temperature value of the resistance temperature detector 3b by comparing the actual measured resistance value RTD calculated by the above formula with the table. The detected temperature value of the resistance temperature detector 3b calculated in this way can be used as the ambient temperature value for cold junction compensation of the thermocouple element 3a, as described above.

[0054] In the second channel CH2, a bias current Ib may be supplied to the fourth resistor R4 from the bias current output terminal IB of the MCU 20. Thus, even when the analog voltage Va input to the detection circuit 18 in the second channel CH2 is minute, the bias current Ib may be supplied to the fourth resistor R4 to increase the potential difference V5 input to the voltage detection terminals V+ and V−, thereby improving the detection accuracy by the MCU 20.

[0055] 8, the circuit configuration is such that the sense current Is2 does not flow to the second channel CH2 side, so there is no effect of voltage drop due to the wiring resistance r of each wire. Therefore, even if the wiring connected to the resistance temperature detector 3b is long, the resistance value RTD of the resistance temperature detector 3b can be detected with high accuracy.

[0056] 9 is a diagram showing another example of the circuit configuration of the detection circuit 18 in FIG. 2 together with the peripheral configuration when the analog voltage Va from the resistance temperature detector 3b is input as the analog signal Sa. In the configuration example shown in FIG. 9, two channels (first channel CH1 and second channel CH2) of the input connector 17 are connected to the resistance temperature detector 3b by a three-wire system.

[0057] In this configuration example, the circuit configuration of the detection circuit 18A corresponding to the first channel CH1 is switched so that a sense current Is3 is applied to the resistance temperature detector 3b from the sense current output terminal IS2 and a potential difference V6 (including a voltage drop due to the wiring resistance r between the resistance temperature detector 3b and the positive input terminal 24a and the wiring resistance r between the resistance temperature detector 3b and the negative input terminal 24b) generated across the resistance temperature detector 3b by the sense current Is3 is measured. Specifically, the switches SW3 and SW4 are switched on and the switches SW1, SW2, and SW5 are switched off, so that the sense current Is3 is supplied from the sense current output terminal IS3 to the resistance temperature detector 3b. At this time, the potential difference V6 across the voltage detection terminals V+ and V− of the first channel CH1 is expressed by the following equation using the resistance value RTD of the resistance temperature detector 3b, the wiring resistance r, and the sense current Is3: V6 = (RTD + r + r) × Is3 (5-1)

[0058] The circuit configuration of the detection circuit 18B corresponding to the second channel CH2 is switched so as to measure a potential difference V7 (including a voltage drop due to the wiring resistance r between the resistance temperature detector 3b and the positive input terminal 24a) occurring across the resistance temperature detector 3b. Specifically, the switches SW3 and SW4 are switched to the on state, and the switches SW1, SW2, and SW5 are switched to the off state. At this time, the potential difference V7 across the voltage detection terminals V+ and V- of the second channel CH2 is expressed by the following equation using the resistance value RTD of the resistance temperature detector 3b, the wiring resistance r, and the sense current Is3: V7 = (RTD + r) × Is3 (5 - 2)

[0059] Then, the input value calculation unit 26 cancels the term of the wiring resistance r using the above equations (5-1) and (5-2) as in the following equation. 2V7-V6=RTD×Is3 (5-3) By modifying this equation, the resistance value RTD of the resistance temperature detector 3b can be calculated by the following equation. RTD = (2V2 - V1) / Is3 (5-4)

[0060] In this way, in the embodiment shown in FIG. 9, by eliminating the effect of voltage drop due to wiring resistance caused by the wiring cables of each channel, it is possible to detect the resistance value RTD of the resistance temperature detector with high accuracy using a three-wire system.

[0061] In addition, within the scope of the present disclosure, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described embodiments may be combined as appropriate.

[0062] The contents described in each of the above embodiments can be understood, for example, as follows.

[0063] (1) An analog input module according to one aspect includes: An analog input module having a plurality of channels for detecting an analog signal input from a controlled object, Each of the plurality of channels comprises: an input terminal to which the analog signal can be input; a detection circuit for detecting the analog signal input to the input terminal as a voltage signal; an input value calculation unit for calculating an input value of the analog signal based on the voltage signal detected by the detection circuit; a circuit switching unit for switching the circuit configuration of the detection circuit based on the type of the analog signal; Equipped with The circuit switching unit switches the circuit configuration based on a setting signal received from a calculation device that performs calculation processing using the input values ​​calculated by the input value calculation units of the plurality of channels.

[0064] According to the above aspect (1), in each of the multiple channels of the analog input / output module, the circuit configuration of the detection circuit is switched based on the type of analog signal input to the input terminal, so that the analog signal input to the input terminal is detected as a voltage signal. The voltage signal detected by the detection circuit is converted into an input value of the analog signal. By switching the circuit configuration of the detection circuit in this way, it is possible to realize an analog input module that can detect input values ​​of different types of analog signals using a common module configuration. Furthermore, the circuit configuration of the detection circuit in each channel is switched based on a setting signal received from a calculation device that performs arithmetic processing using the input values ​​calculated by the input / output calculation unit of each channel. That is, the circuit configuration of the detection circuit is switched to correspond to the type of analog signal specified by a higher-level calculation device that performs arithmetic processing using the input values ​​of the analog signal detected in each channel of the analog input module. This makes it possible to switch the circuit configuration suitable for detecting the input values ​​of the analog signal required for arithmetic processing performed by the calculation device.

[0065] (2) In another embodiment, in the above embodiment (1), The plurality of channels each include a plurality of the detection circuits capable of detecting the analog signals independently of one another.

[0066] According to the above aspect (2), the detection circuits of each channel of the analog input module can detect the input values ​​of the analog signals independently of each other by switching the circuit configuration in accordance with the analog signals input to each channel.

[0067] (3) In another aspect, in the above aspect (1) or (2), When the analog signal is an analog current, the circuit switching unit switches the circuit configuration so that the analog current is detected as the voltage signal.

[0068] According to the above aspect (3), by switching the circuit configuration of the detection circuit so that the analog current input to the input terminal is detected as a voltage signal, the input value of the analog current input to the input terminal can be suitably detected.

[0069] (4) In another embodiment, in any one of the above (1) to (3), When the analog signal is an analog voltage, the circuit switching unit switches the circuit configuration to include a voltage dividing circuit for dividing the analog voltage so that the voltage signal is equal to or lower than an allowable voltage of the circuit configuration.

[0070] According to the above aspect (4), by switching the circuit configuration of the detection circuit so that the analog voltage input to the input terminal is detected as a voltage signal divided by the voltage divider circuit to a voltage equal to or lower than the allowable voltage, the input value of the analog voltage input to the input terminal can be suitably detected.

[0071] (5) In another embodiment, in any one of the above (1) to (4), When the analog signal is an analog voltage from a thermocouple element, the circuit switching unit switches the circuit configuration so that an amplifier circuit for amplifying the analog voltage into the voltage signal is included.

[0072] According to the above aspect (5), even if the analog voltage from the thermocouple element input to the input terminal is small, the analog voltage is detected as a voltage signal amplified by the amplifier circuit, so that the input value of the temperature measured by the thermocouple element can be suitably detected based on the analog voltage input to the input terminal.

[0073] (6) In another embodiment, in the above embodiment (5), The circuit switching unit switches the circuit configuration so that the voltage signal is fixedly set to a predetermined voltage when a break occurs in the wiring between the thermocouple element and the thermocouple.

[0074] According to the above aspect (6), the circuit configuration of the detection circuit is switched so that the voltage signal is fixed to a predetermined voltage when a break occurs in the wiring between the thermocouple element. This makes it possible to preferably prevent the control state from becoming unstable even when a break occurs in the external wiring and the temperature measured by the thermocouple element cannot be detected.

[0075] (7) In another embodiment, in any one of the above (1) to (6), The circuit switching unit switches the circuit configuration so that when a sense current is applied to the resistance thermometer via the input terminal, the potential difference between both ends of the resistor through which the sense current flows and the potential difference between both ends of the resistance thermometer are input as the analog signal.

[0076] According to the above aspect (7), the resistance value of the resistance thermometer detector connected to the input terminal can be detected using a two-wire method. Specifically, by switching the circuit configuration of the detection circuit, when a sense current is applied to the resistance thermometer detector via the input terminal, the potential difference between both ends of the resistor through which the sense current flows and the potential difference generated between both ends of the resistance thermometer detector are detected. This makes it possible to suitably detect the resistance value of the resistance thermometer detector based on the sense current, which can be calculated from the potential difference between both ends of the resistor, and the potential difference between both ends of the resistance thermometer.

[0077] (8) In another embodiment, in any one of the above (1) to (7), the plurality of channels include the detection circuits corresponding to first and second channels, each capable of detecting the analog signal independently of the other; The circuit switching unit In the detection circuit corresponding to the first channel, the circuit configuration is switched so as to detect a potential difference between both ends of a resistor through which a sense current flows when a sense current is applied to a resistance temperature detector connected to the input terminal; In the detection circuit corresponding to the second channel, the circuit configuration is switched so as to detect a potential difference between both ends of the resistance temperature detector; The input value calculation unit calculates the resistance value of the resistance temperature detector based on the sense current calculated based on the potential difference between both ends of the resistor and the potential difference between both ends of the resistance temperature detector.

[0078] According to the above aspect (8), a detection circuit corresponding to the first channel applies a sense current to the resistance thermometer detector, and a detection circuit corresponding to the second channel detects the potential difference between both ends of the resistor through which the sense current flows and the potential difference between both ends of the resistance thermometer detector. This makes it possible to suitably calculate the resistance value of the resistance thermometer detector in a four-wire system based on the sense current calculated from the potential difference between both ends of the resistor and the potential difference between both ends of the resistance thermometer detector.

[0079] (9) In another embodiment, in any one of the above (1) to (8), the plurality of channels include the detection circuits corresponding to first and second channels, each capable of detecting the analog signal independently of the other; The circuit switching unit In the detection circuit corresponding to the first channel, the circuit configuration is switched so as to detect a potential difference between both ends of a resistor through which a sense current flows when the sense current is applied to the resistance temperature detector connected to the input terminal, and a first potential difference between both ends of the resistance temperature detector; switching the circuit configuration in the detection circuit corresponding to the second channel so as to detect a second potential difference between both ends of the resistance temperature detector; The input value calculation unit calculates the resistance value of the resistance temperature detector based on the sense current, the first potential difference, and the second potential difference, which are calculated based on the potential difference between both ends of the resistor.

[0080] According to the above aspect (9), the detection circuit corresponding to the first channel applies a sense current to the resistance temperature detector and detects a first potential difference, and the detection circuit corresponding to the second channel detects a second potential difference across the resistance temperature detector, thereby making it possible to suitably calculate the resistance value of the resistance temperature detector in a three-wire system based on the sense current, the first potential difference, and the second potential difference.

[0081] (10) A control system according to one aspect includes: An analog input module according to any one of the above aspects (1) to (9); the arithmetic unit; Equipped with.

[0082] According to the above aspect (10), a control system capable of suitably controlling a controlled object can be realized by performing arithmetic processing using the input value of the analog signal detected by the analog input module. [Explanation of symbols]

[0083] 1. Control System 2 Input / Output Modules 3. Control Objects 3a Thermocouple element 12. Communication Networks 14 Analog Input Modules 16 Input / Output Adapters 17 Input Connector 18 Detection circuit 20 MCU 24 input terminals 24a Positive input terminal 24b Negative input terminal 26 Input value calculation section 28 Circuit switching unit 30 Isolated power supply 32 DC / DC power supply 34 SPI communication isolation section 38 Voltage divider circuit

Claims

1. An analog input module having a plurality of channels for detecting an analog signal input from a controlled object, Each of the plurality of channels comprises: an input terminal to which the analog signal can be input; a detection circuit for detecting the analog signal input to the input terminal as a voltage signal; an input value calculation unit for calculating an input value of the analog signal based on the voltage signal detected by the detection circuit; a circuit switching unit for switching the circuit configuration of the detection circuit based on the type of the analog signal; Equipped with The circuit switching unit switches the circuit configuration based on a setting signal received from a calculation device that performs calculation processing using the input values ​​calculated by the input value calculation units of the multiple channels.

2. 2. The analog input module according to claim 1, wherein the plurality of channels each include a plurality of the detection circuits capable of detecting the analog signal independently of one another.

3. 3. The analog input module according to claim 1, wherein, when the analog signal is an analog current, the circuit switching section switches the circuit configuration so that the analog current is detected as the voltage signal.

4. 3. The analog input module according to claim 1, wherein, when the analog signal is an analog voltage, the circuit switching unit switches the circuit configuration to include a voltage divider circuit that divides the analog voltage so that the voltage signal is equal to or lower than a tolerable voltage of the circuit configuration.

5. 3. The analog input module according to claim 1, wherein the circuit switching unit switches the circuit configuration so that an amplifier circuit for amplifying the analog voltage into the voltage signal is included when the analog signal is an analog voltage from a thermocouple element.

6. 6. The analog input module according to claim 5, wherein the circuit switching section switches the circuit configuration so that the voltage signal is fixedly set to a predetermined voltage when a break occurs in a wiring between the thermocouple element and the circuit switching section.

7. 3. The analog input module according to claim 1, wherein the circuit switching unit switches the circuit configuration so that when a sense current is applied to the resistance temperature detector via the input terminal, a potential difference between both ends of a resistor through which the sense current flows and a potential difference between both ends of the resistance temperature detector are input as the analog signal.

8. the plurality of channels include the detection circuits corresponding to first and second channels, each capable of detecting the analog signal independently of the other; The circuit switching unit In the detection circuit corresponding to the first channel, the circuit configuration is switched so as to detect a potential difference between both ends of a resistor through which a sense current flows when a sense current is applied to a resistance temperature detector connected to the input terminal; In the detection circuit corresponding to the second channel, the circuit configuration is switched so as to detect a potential difference between both ends of the resistance temperature detector; 3. The analog input module according to claim 1, wherein the input value calculation unit calculates the resistance value of the resistance temperature detector based on the sense current calculated based on the potential difference between both ends of the resistor and the potential difference between both ends of the resistance temperature detector.

9. the plurality of channels include the detection circuits corresponding to first and second channels, each capable of detecting the analog signal independently of the other; The circuit switching unit In the detection circuit corresponding to the first channel, the circuit configuration is switched so as to detect a potential difference between both ends of a resistor through which a sense current flows when the sense current is applied to the resistance temperature detector connected to the input terminal, and a first potential difference between both ends of the resistance temperature detector; switching the circuit configuration in the detection circuit corresponding to the second channel so as to detect a second potential difference between both ends of the resistance temperature detector; 3. The analog input module according to claim 1, wherein the input value calculation unit calculates the resistance value of the resistance temperature detector based on the sense current, the first potential difference, and the second potential difference, which are calculated based on a potential difference between both ends of the resistor.

10. an analog input module according to claim 1 or 2; the arithmetic unit; A control system comprising:

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