Surge protection devices, surge protection systems, and transmitters

Abstract

Detecting the degradation of surge protection measures improves the reliability of the transmitter. [Solution] The surge protection device 1 is mounted on the transmitter. The terminal block screw portions 12 and 13 are connected to a cable that transmits signals from an external device. The connector is detachable from the connector member of the transmitter and outputs input signals from the terminal block screw portions 12 and 13 to the connector member. The surge protection element absorbs surge current when a surge voltage is applied to the connector member from the terminal block screw portions 12 and 13. The terminal connector portion 11 is connected to the terminal block screw portions 12 and 13 via the surge protection element.

Description

Technical Field

[0001] The present invention relates to a surge protection device, a surge protection system, and a transmitter.

Background Art

[0002] Conventionally, in the process control of various plants using oil, petrochemicals, chemicals, gas, etc., field devices such as pressure transmitters are used for the controller to stably control the process. Based on the information obtained by the field devices, the plant control system controls and manages the plant.

[0003] Generally, a field device has a power supply terminal and receives power supply necessary for operation by connecting a power cable to the power supply terminal. Also, in the case of a two-wire transmitter, the power cable also serves as a current output signal cable that varies in the range of 4 - 20 mA.

[0004] A momentary and large abnormal voltage called a surge voltage may be mixed into the power cable due to the influence of lightning strikes or high-voltage equipment. To protect the field device from this surge voltage, a surge protection device (also called a lightning arrester, arrester, surge absorber, transient protection device, etc.) is used.

[0005] The surge protection device may be mounted on the circuit board of the field device or mounted on the field device as a surge protection module. The surge protection device used as a surge protection module has a pair of positive and negative terminals for connecting to the power supply terminal of the field device to be protected, and a surge protection element is connected between those terminals.

[0006] Surge protection elements include metal oxide varistors, avalanche diodes, gas-filled discharge tubes, and surge protection thyristors. Filter functions for noise reduction and other purposes are sometimes incorporated into surge protection devices. Some surge protection devices are soldered to the casing of field equipment, making replacement difficult.

[0007] Furthermore, some lighting fixtures have replaceable surge protection modules. Centrifugal compressors also have a function to detect compressor surges. Additionally, some devices equipped with temperature sensors have replaceable surge protection devices. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] U.S. Patent Application Publication No. 2010 / 0127625 [Patent Document 2] U.S. Patent Application Publication No. 2017 / 0284410 [Patent Document 3] China Utility Model No. 203385492 Specification [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] However, when a surge voltage occurs, the surge protection device blocks the leakage of the surge voltage to the field equipment, but in the process, the surge protection element is damaged and deteriorates. With conventional surge protection devices in field equipment, it was difficult to detect the deterioration of the surge protection element, making it difficult to determine the appropriate replacement time. Similarly, it is difficult to detect the deterioration of the surge protection element in lighting fixtures equipped with surge protection modules, centrifugal compressors with a function to detect compressor surges, and temperature sensors with replaceable surge protection devices. Therefore, it has been difficult to improve the reliability of field equipment such as transmitters.

[0010] Furthermore, in the case of surge protection devices soldered to the casing of field equipment, if the surge protection device deteriorates, the entire casing of the field equipment must be replaced, making replacement difficult and hindering the improvement of the reliability of field equipment such as transmitters. In addition, replacing the entire casing of field equipment increases operating costs. Moreover, since lighting fixtures and centrifugal compressors have different structures from field equipment, it is difficult to directly apply their mechanisms to the surge protection devices of field equipment.

[0011] One aspect of the present invention is to improve the reliability of the transmitter by detecting the deterioration of surge protection measures. [Means for solving the problem]

[0012] A surge protection device relating to one side is mounted on a transmitter and has the following parts: A signal terminal to which a cable transmitting signals from an external device is connected. A connector is detachable from the connector member of the transmitter and outputs the input signal from the signal terminal to the connector member. A surge protection element absorbs surge current when a surge voltage is applied from the signal terminal to the connector member. The terminal connector is connected to the signal terminal via the surge protection element. [Effects of the Invention]

[0013] According to the present invention, it is possible to detect deterioration of surge protection measures and improve the reliability of a transmitter.

Brief Description of the Drawings

[0014] [Figure 1] It is a perspective view of a differential pressure / pressure transmitter. [Figure 2] It is a perspective view of a surge protection device. [Figure 3] It is a front view of the terminal block side of the surge protection device. [Figure 4] It is a front view of the circuit board side of the surge protection device. [Figure 5] It is a figure showing the surge protection device with the circuit board removed. [Figure 6] It is a figure showing a part of the wiring of the surge protection device. [Figure 7] It is a figure showing the measurement principle of a tester. [Figure 8] It is a figure showing a self-diagnosis circuit mounted on the surge protection device according to the second embodiment. [Figure 9] It is a configuration diagram showing an outline of an intercommunication type transmitter according to the fifth embodiment.

Modes for Carrying Out the Invention

[0015] Hereinafter, embodiments of the transmitter will be described with reference to the drawings. In addition, the same reference numerals are assigned to the same elements, and duplicate explanations will be omitted as appropriate. Also, each embodiment can be appropriately combined within a non-contradictory range.

[0016] (First Embodiment) (Overall Configuration) FIG. 1 is a perspective view of a differential pressure / pressure transmitter. The differential pressure / pressure transmitter 100 is an example of a field device (transmitter). The housing 2 of the differential pressure / pressure transmitter 100 has a terminal chamber and a circuit chamber separated by a wall. The terminal chamber is a space opened toward the outside visible in FIG. 1. In the terminal chamber, which is one of the internally partitioned spaces, a surge protection device 1 is arranged in the differential pressure / pressure transmitter 100.

[0017] On the side of the circuit chamber, an internal circuit including resistors and amplifiers for differential pressure and pressure transmission is arranged. On the terminal chamber side of the wall separating the terminal chamber and the circuit chamber of the differential pressure and pressure transmitter 100, a connector member (not shown) for transmitting signals to the internal circuit is provided.

[0018] The differential pressure and pressure transmitter 100 receives the input of a signal transmitted from a higher-level process control device via the surge protection device 1. Then, based on the received signal, the differential pressure and pressure transmitter 100 notifies an external device of a control instruction from the higher-level process control device by transmitting a signal indicating the measurement result generated by the internal circuit to the external device.

[0019] The surge protection device 1 has a shape that fits inside the differential pressure and pressure transmitter 100. And the surge protection device 1 has screws 14 to 16 for fixing the input / output terminals for receiving the input signal to the differential pressure and pressure transmitter 100 and for transmitting the output signal from the differential pressure and pressure transmitter 100 to the screw part. By the screws 14 to 16 and the screw part, for example, wiring extending from a higher-level process control device is connected.

[0020] Also, the surge protection device 1 has a circuit board 20 in the direction toward the internal space of the differential pressure and pressure transmitter 100. On the circuit board 20, a ground terminal 19 is provided at a position separated from the screw part to which the screws 14 to 16 are connected. Also, the connection terminal of the circuit board 20 and the connector member provided on the internal wall of the differential pressure and pressure transmitter 100 are detachable. By connecting the connection terminal of the circuit board 20 and the connector member, the input / output terminals of the surge protection device 1 and the internal circuit of the differential pressure and pressure transmitter 100 are connected.

[0021] The surge protection device 1 receives the input of the power supply supplied from a higher-level process control device and the input of the field communication signal sent from the higher-level process control device at the input / output terminals. Then, the surge protection device 1 transmits the signal from the higher-level process control device to the internal circuit of the differential pressure and pressure transmitter 100 via the connection terminal of the circuit board 20 and the connector member connected to the connection terminal.

[0022] Furthermore, when a surge occurs and the surge protection device 1 receives a surge current input, it absorbs the surge current with a surge protection element and directs the surge current to ground via the ground terminal 19. This prevents the surge current from flowing through the internal wiring of the differential pressure / pressure transmitter 100, thus protecting the circuit of the differential pressure / pressure transmitter 100 from surge current.

[0023] (Details of surge protection device) Figure 2 is a perspective view of the surge protection device. Figure 2 shows the surge protection device 1, which is in the state shown in Figure 1, removed from the partitioned space inside the differential pressure / pressure transmitter 100, and with screws 14-16 removed. Figure 3 is a front view of the terminal block side of the surge protection device.

[0024] As shown in Figures 2 and 3, the surge protection device 1 has a main body case 10. The surge protection device 1 also has removable screws 14-16, an earth terminal 19, and a circuit board 20. The main body case 10 and the circuit board 20 constitute the housing of the surge protection device 1.

[0025] The surge protection device 1 has terminal block screw portions 12 and 13 on the main body case 10. As shown in Figure 2, the terminal block screw portion 13 actually has two screw portions, but here it is referred to collectively as the terminal block screw portion 13. Note that the terminal block screw portion 13 may not be used depending on the type of equipment on which the surge protection device 1 is mounted. Furthermore, the surge protection device 1 has a terminal connector portion 11. In addition, the surge protection device 1 has screw fixing portions 17 and 18 on the main body case 10.

[0026] Screw 14 is screwed into the terminal block screw portion 12, sandwiching the wiring extending from the external device, and is fixed in place. Screws 15 and 16 are screwed into the two screw portions of the terminal block screw portion 13, respectively, sandwiching the wiring extending from the external device, and are fixed in place. Here, screw 16 and the screw 16 side of the terminal block screw portion 13 may not be used depending on the type of equipment on which the surge protection device 1 is mounted. The main body case 10 is fixed to the terminal chamber portion of the housing 2 of the differential pressure / pressure transmitter 100 by screw fixing portions 17 and 18.

[0027] Here, the combination of terminal block screw portion 12 and screw 14, and the combination of terminal block screw portion 13 and screws 15 and 16, each constitute an example of a "signal terminal." Cables that transmit signals from external equipment such as higher-level process equipment are connected to these signal terminals. The combination of terminal block screw portion 12 and screw 14, and the combination of terminal block screw portion 13 and screws 15 and 16, are both arranged on top of the main body case 10 so as to be exposed to the outside. The signal terminals transmit signals from external equipment such as higher-level process equipment to the internal circuit of the differential pressure / pressure transmitter 100 via the connector 23 and the connector member of the differential pressure / pressure transmitter 100.

[0028] Figure 4 is a front view of the surge protection device from the circuit board side. Figure 5 shows the surge protection device with the circuit board removed.

[0029] As shown in Figure 4, the surge protection device 1 has a positive varistor 21 and a negative varistor 22 on the circuit board 20, a connector 23 which is a connection terminal on the circuit board 20, and positioning holes 24 and 25. The connector 23 is located on the side of the circuit board 20 facing outwards and is exposed to the outside from the main body case 10 which is the housing. The circuit board 20 is attached and fixed to the main body case 10 by tapping screws 26 and 27.

[0030] The positive varistor 21 does not conduct current when the applied voltage is positive and below a predetermined value, and conducts a large current when the applied voltage is greater than the predetermined value in the positive direction. Conversely, the negative varistor 22 has a high resistance when the applied voltage is negative and below a predetermined value in absolute value, and conducts a large current when the absolute value of the voltage is greater than the predetermined value. If a large voltage surge occurs on the positive side, the positive varistor 21 absorbs the surge current. Similarly, if a large voltage surge occurs on the negative side, the negative varistor 22 absorbs the surge current. Both the positive varistor 21 and the negative varistor 22 will degrade if a voltage exceeding the maximum allowable voltage is applied, depending on the duration of the applied voltage.

[0031] Here, the positive varistor 21 and the negative varistor 22 are positioned opposite the differential pressure / pressure transmitter 100 on the circuit board 20, but their placement is not limited to this. For example, the positive varistor 21 and the negative varistor 22 may be positioned on the side of the circuit board 20 facing inward, opposite to the side facing the differential pressure / pressure transmitter 100.

[0032] The positive varistor 21 and negative varistor 22 are examples of a "surge protection element." That is, the surge protection element has a positive varistor 21 that absorbs surge current when a positive surge voltage is applied, and a negative varistor 22 that absorbs surge current when a negative surge voltage is applied. The surge protection element also absorbs surge current when a surge voltage is applied from the signal terminal to the connector member. The positive varistor 21 and negative varistor 22 are arranged inside or on the surface of the main body case 10, which is the housing.

[0033] As shown in Figure 5, the positioning parts 28 and 29 provided inside the main body case 10 are inserted into the positioning holes 24 and 25 of the circuit board 20, thereby positioning the circuit board 20 in a predetermined position relative to the main body case 10. The circuit board 20 is then fixed in place by screwing tapping screws 26 and 27 into the main body case 10.

[0034] When the main case 10 is attached to the housing 2 of the differential pressure transmitter 100, the connector 23 on the circuit board 20 is positioned opposite the connector member located on the wall separating the terminal chamber and the circuit chamber of the differential pressure transmitter 100. Then, when the main case 10 is attached to the housing 2 of the differential pressure transmitter 100, the connector 23 on the circuit board 20 is connected to the connector member of the differential pressure transmitter 100.

[0035] Here, because the connector 23 on the circuit board 20 and the connector member of the differential pressure / pressure transmitter 100 are detachable, the main case 10 to which the circuit board 20 is attached can be detached from the housing 2 of the differential pressure / pressure transmitter 100. In other words, the surge protection device 1 can be easily attached to and detached from the differential pressure / pressure transmitter 100.

[0036] Thus, connector 23 is connected to the internal circuitry built into the differential pressure / pressure transmitter 100. Connector 23 is detachable from the connector component of the differential pressure / pressure transmitter 100 and outputs input signals from the signal terminals to the connector component. Connector 23 is connected to the connector component when the main case 10, which is the housing, is mounted on the differential pressure / pressure transmitter 100, and is disconnected from the connector component when the main case 10, which is the housing, is removed from the differential pressure / pressure transmitter 100.

[0037] The terminal connector section 11 is positioned so as to be exposed to the outside from the main body case 10. The terminal connector section 11 is connected to the signal terminals via surge protection elements, namely the positive side varistor 21 and the negative side varistor 22.

[0038] Figure 6 shows a portion of the wiring of the surge protection device. The terminal block screw portion 12 is connected to the internal circuit of the differential pressure / pressure transmitter 100 via a connector 23 provided on the circuit board 20 and a connector member on the differential pressure / pressure transmitter 100 side connected to the connector 23. The wiring extending from the terminal block screw portion 12 branches off and is connected to one end of the positive side varistor 21. The other end of the positive side varistor 21 is connected to the terminal connector portion 11. An earth terminal 19 is located in the middle of the path connecting the positive side varistor 21 and the terminal connector portion 11.

[0039] Similarly, the terminal block screw portion 13 is connected to the internal circuit of the differential pressure / pressure transmitter 100 via a connector 23 provided on the circuit board 20 and a connector member on the differential pressure / pressure transmitter 100 side connected to the connector 23. The wiring extending from the terminal block screw portion 13 branches off and is connected to one end of the negative side varistor 22. The other end of the negative side varistor 22 is connected to the terminal connector portion 11. An earth terminal 19 is located in the middle of the path connecting the negative side varistor 22 and the terminal connector portion 11.

[0040] In this way, the positive varistor 21 and negative varistor 22, which are signal terminals, and the terminal connector section 11 are connected in such a way that the resistance values ​​of the positive varistor 21 and negative varistor 22 can be measured using a terminal measurement method with a tester. In addition, one end of the positive varistor 21 and negative varistor 22 are connected to the signal terminals, and the other end is connected to ground via the ground terminal 19 mounted on the arrester. Furthermore, the terminal connector section 11 is connected to wiring that is branched off from the wiring that connects the positive varistor 21 and negative varistor 22 to ground.

[0041] With this wiring, when a surge voltage is applied to the terminal block screw portion 12 or 13, the surge current is absorbed by the positive varistor 21 or negative varistor 22 according to its polarity, thereby suppressing the impact on the internal circuitry of the differential pressure / pressure transmitter 100.

[0042] (Degradation detection method) The deterioration of the surge protection device 1 is due to the deterioration of the positive side varistor 21 and the negative side varistor 22. Therefore, in the surge protection device 1 according to this embodiment, the user determines the deterioration of the positive side varistor 21 and the negative side varistor 22 by following the procedure below, and detects the deterioration of the surge protection device 1.

[0043] The user performs the following process using a tester equipped with a constant current power supply and a voltmeter that measures the voltage based on the potential difference generated at the load when current is applied.

[0044] The user connects one end of the tester to the terminal connector section 11 shown in Figure 3 and the other end to the terminal block screw section 12, thereby flowing a constant current between the terminal connector section 11 and the terminal block screw section 12. The user then uses the tester to measure the voltage between the terminal connector section 11 and the terminal block screw section 12.

[0045] Figure 7 illustrates the measurement principle of the tester. Here, we will explain using the case of determining the degradation of the positive side varistor 21 as an example. Resistor R represents the resistance of the positive side varistor 21. Resistors r1 and r2 represent the wiring resistances.

[0046] The user performs a common two-terminal measurement method using a tester. That is, a constant current I generated by the tester's constant current source 101 is passed through a load having the resistance R of the positive varistor 21 and the wiring resistances r1 and r2, as shown in Figure 7. The user then reads the voltage between the terminal connector part 11 and the terminal block screw part 12 using the tester's voltmeter 102. In this case, the load resistance includes the varistor resistance R as well as the wiring resistances r1 and r2, but since the influence of resistances r1 and r2 is small compared to resistance R, the user can determine the deterioration of the positive varistor 21 using this two-terminal measurement method.

[0047] In this embodiment, the explanation was given using a two-terminal measurement method, but it is also possible to perform degradation detection using a four-terminal measurement method. In that case, the influence of wiring resistance can be eliminated, making it possible to perform degradation detection with higher accuracy.

[0048] When the positive varistor 21 fails due to degradation, it enters short-circuit mode, and its resistance decreases. Therefore, the user determines that the positive varistor 21 has degraded if the resistance value obtained from the measured voltage is smaller than a predetermined value. In this way, the user can detect the degradation of the surge protection device 1.

[0049] Furthermore, the user connects one end of the tester to the terminal connector section 11 shown in Figure 3 and the other end to the terminal block screw section 13, thereby flowing a constant current between the terminal connector section 11 and the terminal block screw section 13. The user then uses the tester to measure the voltage between the terminal connector section 11 and the terminal block screw section 13. This allows the user to determine the deterioration of the negative side varistor 22 based on the resistance value obtained from the measured voltage.

[0050] Similarly, when the negative varistor 22 fails due to degradation, it enters short-circuit mode, and its resistance decreases. Therefore, the user determines that the negative varistor 22 is degraded if the resistance value obtained from the measured voltage is smaller than a predetermined value. In this way, the user can detect the degradation of the surge protection device 1.

[0051] Here, a system comprising a differential pressure / pressure transmitter 100, a surge protection device 1, and a user-use tester is an example of a "surge protection system."

[0052] (Exchange method) As described above, the surge protection device 1 can be easily attached to and detached from the differential pressure / pressure transmitter 100. Therefore, if the user detects deterioration of the surge protection device 1, they can loosen the screw fixing parts 17 and 18 and remove the surge protection device 1 from the housing 2 of the differential pressure / pressure transmitter 100. Then, the user can place a new surge protection device 1 in the partitioned space inside the differential pressure / pressure transmitter 100 and fix it to the housing 2 using the screw fixing parts 17 and 18. In this way, the surge protection device 1 can be easily replaced when it deteriorates.

[0053] In the above explanation, a two-wire differential pressure / pressure transmitter 100 was used as an example of a transmission device. However, the surge protection device 1 according to this embodiment is not limited to two-wire differential pressure / pressure transmitters 100. For example, it can also be applied to two-wire field devices such as temperature transmitters, vortex flow meters, and pH meters, or to four-wire field devices powered by commercial power sources such as electromagnetic flow meters, Coriolis flow meters, and ultrasonic flow meters.

[0054] (effect) As described above, the surge protection device 1 according to this embodiment has a terminal connector section 11 for deterioration determination. The user can then use a tester to determine the deterioration of the surge protection device 1 by examining the terminal connector section 11 and the terminal block screw sections 12 and 13.

[0055] Furthermore, the housing 2 of the differential pressure / pressure transmitter 100 has a terminal room and a circuit room separated by a wall. In some conventional field devices, surge protection devices are located in the circuit room. Also, in conventional field devices, it was necessary to connect the terminal room and the circuit room by passing the wiring through the wall of the housing. For this reason, inexpensive soldering was used while considering waterproofing and noise performance. The circuit room is located deep inside the terminal room and is difficult to access directly, and if a surge protection device is located in the circuit room, it is difficult to replace the surge protection device. Even if a surge protection device is located in the terminal room, in many conventional field devices the wiring of the surge protection device is soldered, making it difficult to replace the surge protection device.

[0056] In contrast, the surge protection device 1 according to this embodiment is located on the terminal chamber side of the differential pressure / pressure transmitter 100, and its connection to the internal circuit is detachable via a connector 23, making it easy to replace if it deteriorates.

[0057] Thus, by using the surge protection device 1 according to this embodiment, users can easily determine the replacement timing, which was previously difficult to ascertain, and replace the surge protection device 1 at the appropriate time. In other words, users can replace the surge protection device 1 before it is completely damaged, thereby improving the reliability of the transmitter. Furthermore, it becomes possible to reduce the overall operating costs of the transmitter.

[0058] (Second Embodiment) Next, a second embodiment will be described. The surge protection device 1 according to this embodiment automatically measures the impedance of the circuit including the terminal block screw portion 13 and the terminal connector portion 11, and self-diagnoses deterioration by detecting the leakage current. In the following description, the functions of each part, which are the same as in the first embodiment, will be omitted.

[0059] Figure 8 shows a self-diagnostic circuit mounted on a surge protection device according to the second embodiment. As shown in Figure 8, the surge protection device 1 according to this embodiment has an AD (Analog Digital) converter 31 and an MCU (Micro Controller Unit) 32.

[0060] The AD converter 31 is connected, for example, to both ends of the resistor between the terminal block screw portion 12 and the terminal connector portion 11. More specifically, the AD converter 31 is connected to both ends of the positive side varistor 21 in Figure 6.

[0061] The AD converter 31 can obtain the voltage across the resistor between the terminal block screw portion 12 and the terminal connector portion 11 in Figure 8 by detecting the leakage current flowing from the resistor. The AD converter 31 converts the voltage across the resistor between the terminal block screw portion 13 and the terminal connector portion 11 into a digital signal and outputs it to the MCU 32.

[0062] The MCU32 is connected to the AD converter 31. The MCU32 receives the input voltage across the resistor between the terminal block screw portion 12 and the terminal connector portion 11, which has been converted to a digital signal, from the AD converter 31. Next, the MCU32 measures the impedance of the resistor between the terminal block screw portion 12 and the terminal connector portion 11 to determine the leakage current. Then, the MCU32 measures the resistance value between the terminal block screw portion 12 and the terminal connector portion 11 from the leakage current and impedance.

[0063] The MCU32 determines the degradation of the positive varistor 21 based on the measured resistance value. The MCU32 detects the degradation of the surge protection device 1 based on the positive varistor 21 and the degradation determination result. If degradation of the surge protection device 1 is detected, the MCU32 notifies the user of the degradation detection. For example, the MCU32 may notify the user of the degradation detection by illuminating a warning light (not shown) provided on the surge protection device 1, or it may send a message indicating the degradation detection to the user's terminal device.

[0064] In this embodiment, the resistance between the terminal block screw portion 12 and the terminal connector portion 11, i.e., the resistance of the positive side varistor 21, was described as an example, but the same applies to the resistance between the terminal block screw portion 13 and the terminal connector portion 11, i.e., the resistance of the negative side varistor 22.

[0065] This MCU32 is an example of a control unit. The MCU32 measures the resistance value of the surge protection element from the leakage current between the signal terminal and the terminal connector 11, and detects the deterioration of the surge protection element from the measured resistance value of the surge protection element.

[0066] (effect) As described above, the surge protection device 1 according to this embodiment can automatically detect its own deterioration using the leakage current between the terminal block screw portion 13 and the terminal connector portion 11. This allows users to quickly determine when replacement is needed and replace the surge protection device 1 at the appropriate time. Therefore, it is possible to improve the reliability of field equipment.

[0067] (Third embodiment) Next, a third embodiment will be described. In this embodiment, the surge protection device 1 uses the MCU 32 from the second embodiment to estimate the remaining number of cycles of operation from the resistance values ​​of the positive varistor 21 and the negative varistor 22. The remaining number of cycles of operation indicates how many more times it is possible to absorb surge current and protect the differential pressure / pressure transmitter 100. In the following description, the functions of each part, which are the same as in the second embodiment, will be omitted. In the following description, the positive varistor 21 will be used as an example.

[0068] The MCU32 has pre-existing information about how much the positive varistor 21 resistance value changes during a single surge. In practice, the amount of change during a single surge depends on the surge energy, but in this embodiment, it is determined, for example, from the typical voltage and current required by the standard.

[0069] The MCU32 determines the resistance of the positive varistor 21 from the resistance between the terminal block screw portion 12 and the terminal connector portion 11. Then, based on the current resistance of the positive varistor 21 and information on how much it changes during one lightning surge, the MCU32 estimates how many more surges the positive varistor 21 can withstand, i.e., the remaining number of surges it can withstand. After that, the MCU32 notifies the user of the remaining number of surges the positive varistor 21 can withstand.

[0070] In this embodiment, the positive varistor 21 was used as an example, but the MCU 32 can similarly estimate the remaining number of cycles for the negative varistor 22. Thus, the control unit, the MCU 32, has prior information on the change in the resistance value of the surge protection element due to a single surge, and estimates the remaining number of cycles for the surge protection element based on the measured resistance value and change in the surge protection element.

[0071] (effect) As described above, the surge protection device 1 according to this embodiment can automatically detect the remaining number of cycles of the positive varistor 21 and the negative varistor 22 using the leakage current between the terminal block screw portion 13 and the terminal connector portion 11. This allows the user to quickly determine when replacement is needed and replace the surge protection device 1 at the appropriate time. Therefore, it is possible to improve the reliability of field equipment.

[0072] (Fourth Embodiment) Next, a fourth embodiment will be described. The surge protection device 1 according to this embodiment uses the MCU 32 from the third embodiment to predict the future degradation period and automatically determine when to purchase spare parts for replacement. The following description will use the positive side varistor 21 as an example. In the following description, the functions of each part, as in the third embodiment, will be omitted. The following description will use the positive side varistor 21 as an example.

[0073] The MCU32 has pre-programmed information on how much the resistance value of the positive varistor 21 changes during a single surge, as well as the operating time of the surge protection device 1. The MCU32 also counts the number of surges that have flowed through the positive varistor 21 and maintains the current surge experience count of the positive varistor 21.

[0074] The MCU32 estimates the remaining number of surges the positive varistor 21 has left, based on its current resistance value and how much it changes during a single surge. Next, the MCU32 determines the surge frequency based on the operating time of the surge protection device 1 and the current number of surges experienced by the positive varistor 21.

[0075] Next, the MCU32 calculates the timing of degradation of the positive side varistor 21 using the surge frequency and the remaining number of cycles of the positive side varistor 21. Then, based on the calculated degradation timing, the MCU32 determines when to purchase a spare positive side varistor 21 for replacement. Finally, the MCU32 notifies the user of the timing of the purchase of the spare positive side varistor 21. Alternatively, the MCU32 may be connected to a server of the component supplier via a network, and the MCU32 may automatically purchase the spare positive side varistor 21 from the supplier when the time comes.

[0076] In this way, the control unit MCU32 counts the number of surge occurrences and predicts the degradation time of the surge protection element based on the number of occurrences, operating time, and remaining lifespan. The MCU32 also determines when to purchase a spare surge protection element based on the predicted degradation time.

[0077] (effect) As described above, the surge protection device 1 according to this embodiment can predict when deterioration will occur and determine when to purchase spare parts. This allows users to procure spare parts in advance and replace the surge protection device 1 at the appropriate time. Therefore, it is possible to improve the reliability of field equipment.

[0078] (Fifth embodiment) Next, a fifth embodiment will be described. Figure 9 is a schematic diagram showing the configuration of the intercommunication type transmitter according to the fifth embodiment. The surge protection device 1 according to this embodiment is mounted on the intercommunication transmitter 200.

[0079] As shown in Figure 9, the intercommunication transmitter 200 has a primary transmitter 100A and a secondary transmitter 100B. The intercommunication transmitter 200 can handle various physical quantities of the object being measured. For example, the intercommunication transmitter 200 is a differential pressure transmitter. The intercommunication transmitter 200 will be described below using a differential pressure transmitter as an example.

[0080] The primary transmitter 100A and the secondary transmitter 100B are connected by a communication cable. The primary transmitter 100A and the secondary transmitter 100B can send and receive data from each other via the communication cable. The primary transmitter 100A is positioned on the high-pressure side of the pressure generated by the object being measured. The secondary transmitter 100B is positioned on the low-pressure side of the pressure generated by the object being measured.

[0081] The primary transmitter 100A acquires the pressure measured by the secondary transmitter 100B and outputs a signal corresponding to the pressure difference between the pressure measured by the primary transmitter 100A and the pressure measured by the secondary transmitter 100B.

[0082] The primary transmitter 100A is equipped with a surge protection device 1A. The surge protection device 1A is provided with terminal block screw portions 12 and 13, and a terminal connector portion 11, similar to the surge protection device 1 described above.

[0083] The user connects one end of the tester to the terminal connector 11 of the surge protection device 1A and the other end to the terminal block screw 12. The user then performs a two-terminal measurement using the tester and reads the voltage between the terminal connector 11 and the terminal block screw 12. The user determines the degradation of the positive side varistor 21 based on the read voltage.

[0084] Furthermore, the user connects one end of the tester to the terminal connector 11 of the surge protection device 1A and the other end to the terminal block screw portion 13. The user then performs a two-terminal measurement method using the tester and reads the voltage between the terminal connector 11 and the terminal block screw portion 13. Based on the read voltage, the user determines the deterioration of the negative side varistor 22.

[0085] Alternatively, the user may calculate the number of surge occurrences from the deterioration status of the positive varistor 21 and the negative varistor 22 of the surge protection device 1A, and then determine the deterioration status of the surge protection device 1A from the calculated number of surge occurrences.

[0086] Furthermore, even in this configuration of the intercommunication transmitter 200, it is possible to equip the surge protection device 1A with the AD converter 31 and MCU 32 shown in Figure 8 to automatically determine degradation. In that case, the MCU 32 can be used to estimate the remaining number of cycles, predict future degradation timing, and automatically determine when to purchase spare parts for replacement.

[0087] Here, the primary transmitter 100A is an example of a "first transmitter," and the secondary transmitter 100B is an example of a "second transmitter." Also, the surge protection device 1A is an example of a "surge protection device."

[0088] In this embodiment, the explanation was given assuming that the secondary transmitter 100B is not equipped with a surge protection device, but the secondary transmitter 100B may be equipped with a surge protection device. Even in that case, it is not necessary to provide a mechanism for detecting degradation in the surge protection device installed in the secondary transmitter 100B. In that case, the degradation of the surge protection device 1A and the degradation of the surge protection device 1B installed in the secondary transmitter 100B can be considered equivalent. Therefore, the user detects the degradation of the surge protection device 1A and the surge protection device 1B from the degradation determination results of the positive side varistor 21 and the degradation determination results of the negative side varistor 22.

[0089] The surge protection device 1A, which is the first surge protection device, is equipped with signal terminals that consist of a combination of a terminal block screw portion 12 and a screw 14 to which a cable transmitting signals from an external device is connected, and a combination of a terminal block screw portion 13 and screws 15 and 16. The surge protection device 1A is also equipped with a connector 23 that is detachable from the connector member of the primary transmitter 100A, which is the first transmitter, and outputs input signals from the signal terminals to the connector member. The surge protection device 1A is also equipped with a positive varistor 21 and a negative varistor 22, which are surge protection elements that absorb surge current when a surge voltage is applied from the signal terminals to the connector member. The surge protection device 1A is also equipped with a terminal connector portion 11 that is connected to the signal terminals via the surge protection elements.

[0090] (effect) As explained above, even a mutual communication transmitter 200 having a primary transmitter 100A and a secondary transmitter 100B can be equipped with a surge protection device 1A. Furthermore, even with a surge protection device 1A installed in a mutual communication transmitter 200, it is possible to estimate the timing of degradation and determine when to purchase spare parts. This allows users to procure spare parts in advance and replace the surge protection device 1A installed in the mutual communication transmitter 200 at the appropriate time. Therefore, it is possible to improve the reliability of the primary transmitter 100A.

[0091] (system) Unless otherwise specified, the processing procedures, control procedures, specific names, and various data and parameters shown in the above documents and drawings may be changed at will.

[0092] Furthermore, the components of each illustrated device are functionally conceptual and do not necessarily need to be physically configured as shown. In other words, the specific forms of distribution and integration of each device are not limited to those shown. That is, all or part of them can be functionally or physically distributed and integrated in any unit according to various loads and usage conditions.

[0093] Some examples of the combinations of technical features that will be disclosed are listed below.

[0094] (1) A surge protection device mounted on a transmitter, A signal terminal to which a cable transmitting signals from an external device is connected, A connector that is detachable from the connector member of the transmitter and outputs the input signal from the signal terminal to the connector member, A surge protection element that absorbs surge current when a surge voltage is applied from the signal terminal to the connector member, A terminal connector portion connected to the signal terminal via the surge protection element. A surge protection device characterized by being equipped with the following features. (2) The transmitter has a housing that can be detachably mounted on it, The signal terminal, the connector, and the terminal connector portion are arranged so as to be exposed to the outside from the housing. The surge protection element is disposed inside or on the surface of the housing. The surge protection device according to (1), characterized in that (3) The surge protection device according to (2), characterized in that the connector is connected to the connector member when the housing is mounted on the transmitter, and is disconnected from the connector member when the housing is removed from the transmitter. (4) The surge protection device according to any one of (1) to (3), characterized in that the signal terminal and the terminal connector are connected in such a way that the resistance value of the surge protection element can be measured by a terminal measurement method using a tester. (5) The connector member is connected to an internal circuit built into the transmitter. The signal terminal transmits signals from the external device to the internal circuit via the connector and the connector member. A surge protection device according to any one of (1) to (4), characterized by the above. (6) The surge protection element has one end connected to the signal terminal and the other end connected to ground. The terminal connector is connected to a wiring branched from the wiring connecting the surge protection element and the ground. A surge protection device according to any one of (1) to (5), characterized by the above. (7) The surge protection element is, A positive varistor absorbs the surge current when a positive surge voltage is applied, A negative varistor absorbs the surge current when a negative surge voltage is applied. A surge protection device according to any one of (1) to (6), characterized by comprising the following: (8) A surge protection device according to any one of (1) to (7), further comprising a control unit that measures the resistance value of the surge protection element from the leakage current between the signal terminal and the terminal connector portion, and detects the deterioration of the surge protection element from the measured resistance value of the surge protection element. (9) The surge protection device according to (8), characterized in that the control unit has prior information on the amount of change in the resistance value of the surge protection element due to a single surge, and estimates the remaining number of times the surge protection element can withstand based on the measured resistance value of the surge protection element and the amount of change. (10) The surge protection device according to (9), characterized in that the control unit counts the number of surge occurrences and predicts the deterioration time of the surge protection element based on the number of occurrences, operating time, and remaining durability cycles. (11) The surge protection device according to (10), characterized in that the control unit determines the timing for purchasing a spare part of the surge protection element according to the predicted deterioration time. (12) A surge protection system comprising a transmitter, a surge protection device, and a tester, The transmitter is equipped with the surge protection device. The surge protection device is A signal terminal to which a cable transmitting signals from an external device is connected, A connector that is detachable from the connector member of the transmitter and outputs the input signal from the signal terminal to the connector member, A surge protection element that absorbs surge current when a surge voltage is applied from the signal terminal to the connector member, The system includes a terminal connector portion connected to the signal terminal via the surge protection element, The aforementioned tester, A first terminal connected to the aforementioned signal terminal, A second terminal connected to the aforementioned terminal connector, A constant current circuit that flows a constant current between the first terminal and the second terminal, The system includes a measuring circuit for measuring the resistance between the first terminal and the second terminal when the constant current is flowing through the constant current circuit. A surge protection system characterized by the following features. (13) A transmitter having a first transmitter equipped with a surge protection device and a second transmitter equipped with a second surge protection device, The surge protection device is A signal terminal to which a cable transmitting signals from an external device is connected, A connector which is detachable from the connector member of the first transmitter and outputs the input signal from the signal terminal to the connector member, A surge protection element that absorbs surge current when a surge voltage is applied from the signal terminal to the connector member, It comprises a terminal connector portion connected to the signal terminal via the surge protection element. A transmitter characterized by the following features. [Explanation of Symbols]

[0095] 1,1A,1B Surge Protection Device 2 cabinets 11 Terminal connector section 12,13 Terminal block screw section 14, 15, 16 Screw 17,18 Screw fixing part 19. Ground terminal 20 Circuit boards 21. Positive side varistor 22 Negative side varistor 23 Connectors 24,25 Positioning holes 26, 27 Tapping screws 28,29 Positioning section 31 AD Converters 32 MCU 100 Differential Pressure / Pressure Transmitter 100A Primary Transmitter 100B Secondary Transmitter 200 Intercommunication Transmitters

Claims

1. A surge protection device mounted on a transmitter, A signal terminal to which a cable transmitting signals from an external device is connected, A connector that is detachable from the connector member of the transmitter and outputs the input signal from the signal terminal to the connector member, A surge protection element that absorbs surge current when a surge voltage is applied from the signal terminal to the connector member, A terminal connector portion connected to the signal terminal via the surge protection element. A surge protection device characterized by being equipped with the following features.

2. The transmitter has a housing that can be detachably mounted on it, The signal terminal, the connector, and the terminal connector portion are arranged so as to be exposed to the outside from the housing. The surge protection element is disposed inside or on the surface of the housing. The surge protection device according to feature 1.

3. The surge protection device according to claim 2, characterized in that the connector is connected to the connector member when the housing is mounted on the transmitter, and is disconnected from the connector member when the housing is removed from the transmitter.

4. The surge protection device according to claim 1, characterized in that the signal terminal and the terminal connector are connected in such a way that the resistance value of the surge protection element can be measured by a terminal measurement method using a tester.

5. The connector member is connected to an internal circuit built into the transmitter. The signal terminal transmits signals from the external device to the internal circuit via the connector and the connector member. The surge protection device according to feature 1.

6. The surge protection element has one end connected to the signal terminal and the other end connected to ground. The terminal connector is connected to a wiring branched from the wiring connecting the surge protection element and the ground. The surge protection device according to feature 1.

7. The surge protection element is, A positive varistor absorbs the surge current when a positive surge voltage is applied, A negative varistor absorbs the surge current when a negative surge voltage is applied. The surge protection device according to claim 1, characterized by comprising the above.

8. The surge protection device according to claim 1, further comprising a control unit that measures the resistance value of the surge protection element from the leakage current between the signal terminal and the terminal connector portion, and detects the deterioration of the surge protection element from the measured resistance value of the surge protection element.

9. The surge protection device according to claim 8, characterized in that the control unit has prior information on the amount of change in the resistance value of the surge protection element due to a single surge, and estimates the remaining number of times the surge protection element can withstand based on the measured resistance value of the surge protection element and the amount of change.

10. The surge protection device according to claim 9, characterized in that the control unit counts the number of surge occurrences and predicts the deterioration time of the surge protection element based on the number of occurrences, operating time, and remaining durability cycles.

11. The surge protection device according to claim 10, characterized in that the control unit determines the timing for purchasing a spare part of the surge protection element according to the predicted deterioration time.

12. A surge protection system comprising a transmitter, a surge protection device, and a tester, The transmitter is equipped with the surge protection device. The surge protection device is A signal terminal to which a cable transmitting signals from an external device is connected, A connector that is detachable from the connector member of the transmitter and outputs the input signal from the signal terminal to the connector member, A surge protection element that absorbs surge current when a surge voltage is applied from the signal terminal to the connector member, The system includes a terminal connector portion connected to the signal terminal via the surge protection element, The aforementioned tester, A first terminal connected to the aforementioned signal terminal, A second terminal connected to the aforementioned terminal connector, A constant current circuit that flows a constant current between the first terminal and the second terminal, The system includes a measuring circuit for measuring the resistance between the first terminal and the second terminal when the constant current is flowing through the constant current circuit. A surge protection system characterized by the following features.

13. A transmitter having a first transmitter equipped with a surge protection device and a second transmitter equipped with a second surge protection device, The surge protection device is A signal terminal to which a cable transmitting signals from an external device is connected, A connector which is detachable from the connector member of the first transmitter and outputs the input signal from the signal terminal to the connector member, A surge protection element that absorbs surge current when a surge voltage is applied from the signal terminal to the connector member, It comprises a terminal connector portion connected to the signal terminal via the surge protection element. A transmitter characterized by the following features.

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