Diagnosis of pulse solenoid i / p function

Abstract

Techniques for diagnosing a fault in a digital solenoid I / P converter are provided herein. A controller of the I / P converter can apply a fixed voltage to the I / P converter, thereby causing an armature to move from a closed position to an open position in a normally functioning I / P converter. The controller can receive an indication of whether a jump in a digital logic line has occurred, which indicates that a current of the I / P coil has reached a desired maximum current level, and an indication of a time elapsed since the fixed voltage was applied. The controller can compare an amount of time elapsed since the fixed voltage was applied to an expected amount of time elapsed after which, for a normally functioning I / P coil, a jump in the digital logic line would occur, and diagnose a fault in the I / P converter based on the comparison.

Description

Technical Field

[0001] This disclosure generally relates to converters, and more specifically, to electro-pneumatic converters and related methods. Background Technology

[0002] Control valves (e.g., spool valves, rotary valves, axial flow valves, ball valves, etc.) are commonly used in industrial processes, such as oil and gas pipeline distribution systems and chemical processing plants, to control the flow of process fluids. These control valves are automated using pressure-operated actuators controlled by remotely operated field instruments. The field instruments communicate with a process control computer to command changes in fluid flow within the valve, thereby achieving the desired control strategy through the pressure-operated actuator. Electro-pneumatic (I / P) converters (e.g., current-to-pressure transducers) are typically used in the field instruments to provide the conversion of electrical signals to volumetric flow rate or pressure output (i.e., pneumatic pressure signals) to control the actuators, thereby controlling the control valves.

[0003] An exemplary electro-pneumatic converter (e.g., as discussed in U.S. Patent No. 10,422,438B2, the entire contents of which are incorporated herein by reference) can be fluidly coupled between a supply pressure source that supplies pressurized fluid and a downstream device (e.g., a pneumatic relay) that uses the pressurized fluid to control a process control device (e.g., an actuator). The exemplary electro-pneumatic converter can control the flow of pressurized fluid between the supply pressure source and the downstream device. Specifically, the exemplary electro-pneumatic converter can operate between a closed state (sometimes referred to as closed or unlocked) and an open state (sometimes referred to as open or latched). In the closed state, no pressurized fluid is supplied to the downstream device. In the open state, an electrical signal in the form of current is applied to the electro-pneumatic converter, which allows the flow of pressurized fluid to the downstream device and thus converts the electrical input signal into a pneumatic pressure signal.

[0004] An electro-pneumatic converter utilizes a solenoid with a coil and a movable armature to control the flow of pressurized fluid between a supply port and one or more output ports. In some examples, the electro-pneumatic converter includes an axial passage between the supply port and a discharge port. One or more output ports are fluidly coupled to the axial passage and may be coupled to a downstream device (e.g., a pneumatic relay). The supply port receives pressurized fluid from a pressure supply source. The armature is positioned in the axial passage and is movable between a first position and a second position, the first position preventing pressurized fluid from flowing through the axial passage between the supply port and the output port, and the second position allowing pressurized fluid to flow through the axial passage between the supply port and one or more output ports. When the solenoid is activated, the armature moves from the first position to the second position to allow pressurized fluid to flow to one or more output ports. In the first position, when the supply port is blocked, the discharge port is unlocked, and one or more output ports are fluidly coupled to the discharge port (e.g., vented to the atmosphere). In the second position, when the supply port is unlocked, the armature blocks the discharge port, thereby allowing pressurized fluid to flow from the supply port to one or more output ports. The solenoid can be activated and deactivated to move the armature back and forth between a first position and a second position in the channel, thereby controlling the flow of pressurized fluid to one or more output ports. This geometry allows the armature to move a relatively small distance between a first (closed) position and a second (open) position.

[0005] Specifically, digital solenoid I / P converters typically include an armature that is initially spring-biased to the closed position when no voltage is applied. To actuate the armature, a fixed voltage is applied until a desired maximum current level is reached. Once the maximum current level is reached, a reduced voltage is applied to hold the armature in the pulled-in position (i.e., the open position). When the voltage is removed (or, in some examples, when a small negative voltage is applied), the spring force returns the armature to the closed position.

[0006] The objective is to test the proper functioning of the digital solenoid I / P converter coil and drive circuit, as well as to detect malfunctions in either the coil or the drive circuit. When a malfunction occurs, the goal is to diagnose the cause of the failure so that any problems with the coil or drive circuit can be corrected. Summary of the Invention

[0007] In one aspect, a method is provided for diagnosing a fault in a digital solenoid I / P converter in a process control system, wherein the digital solenoid I / P converter includes an I / P coil and a drive circuit, and wherein the solenoid I / P converter, when actuated, moves an armature from a closed position to an open position, the method comprising: determining that a fixed voltage has been applied to the I / P coil at a first time; and receiving from a current sensor an indication of a current level associated with the I / P coil; performing a first comparison of the indication of the current level associated with the I / P coil and a desired maximum current level; based on the comparison, causing a digital logic line to switch when the current level associated with the I / P coil reaches the desired maximum current level; and receiving from a timer an indication of a current level from the first time to a second time. The system provides an indication of the amount of time that has elapsed, the second time being the time associated with a transition of the digital logic line; performs a second comparison of (i) the amount of time elapsed from the first time to the second time and (ii) the expected amount of time elapsed since the fixed voltage was applied to the I / P coil, after which the digital logic line will transition for a normally functioning I / P coil and the drive circuit; based on the second comparison, determines whether the I / P coil and the drive circuit are functioning normally or whether one or more of the I / P coil or the drive circuit has failed; and based on the determination that one or more of the I / P coil or the drive circuit has failed, causes the controller to take a control action that changes the operation of the process control system.

[0008] On the other hand, a system is provided for diagnosing faults in a digital solenoid I / P converter in a process control system. The system includes: a digital solenoid I / P converter including an I / P coil and drive circuitry, the digital solenoid I / P converter being configured to move an armature from a closed position to an open position when actuated; a controller configured to apply a fixed voltage to the I / P coil at a first instant; a current sensor configured to sense a current quantity associated with the I / P coil; a timer configured to determine an amount of time elapsed since the first instant; and a diagnostic circuit configured to: perform a first comparison of the sensed current quantity associated with the I / P coil with a desired maximum current level; and based on the first comparison, enable data logic... The logic line switches when the sensed current associated with the I / P coil reaches the desired maximum current level; receives from the timer an indication of the amount of time elapsed from the first time to the second time associated with the switching of the digital logic line; performs a second comparison of (i) the amount of time elapsed from the first time to the second time and (ii) the expected amount of time elapsed since the fixed voltage was applied to the I / P coil, after which a digital logic line switching will occur for a normally functioning I / P coil and drive circuit; and, based on the second comparison, determines whether the I / P coil and the drive circuit are functioning normally or whether one or more of the I / P coil or the drive circuit have failed. Attached Figure Description

[0009] Figure 1 It is a cross-sectional view of an exemplary electric-pneumatic converter having an exemplary armature in the first (closed) position.

[0010] Figure 2 yes Figure 1 A cross-sectional view of an exemplary electric-pneumatic converter, wherein the exemplary armature is in the second (open) position.

[0011] Figure 3 It shows the use of Figure 1 An exemplary graph showing the input current applied and the output pressure obtained by an exemplary electric-pneumatic converter.

[0012] Figure 4 Includes several exemplary graphs illustrating the changes in voltage applied by an exemplary, functionally functioning electric-pneumatic converter over time, the changes in current generated over time, and the changes in logic line trips over time.

[0013] Figure 5Includes several exemplary graphs illustrating the changes in applied voltage over time, generated current over time, and logic line transitions over time for an exemplary electro-pneumatic converter with an open circuit in the coil or drive circuit.

[0014] Figure 6 Includes several exemplary graphs illustrating the changes in applied voltage over time, generated current over time, and logic line transitions over time for an exemplary electro-pneumatic converter with a short circuit in the coil or drive circuit.

[0015] Figure 7 Several exemplary graphs are included, illustrating the changes in applied voltage over time, generated current over time, and logic line transitions over time for an exemplary electro-pneumatic converter associated with an armature that is already in the locked position when actuated or never moves from the unlocked position to the locked position.

[0016] Figure 8 Examples are given for diagnosis. Figure 1 An exemplary diagnostic circuit for possible malfunctions of an exemplary electric-pneumatic converter.

[0017] Figure 9 This indicates that diagnostics can be implemented by the controller. Figure 1 A flowchart illustrating an exemplary method for addressing potential failures of an exemplary electric-pneumatic converter. Detailed Implementation

[0018] As described above, a digital solenoid I / P converter typically includes an armature that is initially spring-biased to the closed position when no voltage is applied. To actuate the armature, a fixed voltage is applied until a desired maximum current level is reached. Once the maximum current level is reached, a reduced voltage is applied to hold the armature in the pulled-in position (i.e., the open position). When the voltage is removed (or, in some examples, when a small negative voltage is applied), the spring force returns the armature to the closed position.

[0019] This disclosure provides techniques for detecting whether the digital solenoid I / P converter coil and drive circuit are functioning properly, and whether a fault occurs in the digital solenoid I / P converter coil and / or drive circuit. Furthermore, this disclosure provides techniques for diagnosing possible causes of faults in the digital solenoid I / P converter coil or drive circuit, i.e., enabling the correction of any problems with the digital solenoid I / P converter coil or drive circuit.

[0020] Using this technology, the digital logic lines switch or toggle when the desired maximum current is reached, and reset when an I / P converter armature "unlock" command is sent. The amount of time elapsed between the initial application of voltage and the switching of the digital logic lines can be used to determine whether the I / P converter is functioning correctly, or whether it is malfunctioning in some way (e.g., whether there is an open circuit in the coil, a short circuit in the coil, or the armature not moving).

[0021] For example, using a 650-ohm coil, a 7V drive rail, and a maximum current of 5mA, a normally functioning I / P converter takes approximately 8ms from actuation to reaching the 5mA maximum current. Conversely, when an open circuit exists in the coil or drive circuit, the logic line will never transition because no current is generated. Furthermore, using a shorted coil, a 7V drive rail, and a maximum current of 5mA, the current will rise rapidly when the coil is shorted due to the elimination of coil impedance. Therefore, when the coil is shorted, it takes only approximately 0.1ms from actuation to reaching the 5mA current level. Finally, when the armature is already pulled in or cannot be pulled in at actuation, the time to reach the 5mA current level is reduced because the current does not decrease (because the armature has not moved). Therefore, when the armature has not moved, it will take approximately 4ms from actuation to reaching the 5mA current level.

[0022] Therefore, this technique includes diagnosing faults in the I / P converter coil and drive circuit by determining whether the digital logic line has transitioned, and if so, further determining the amount of time elapsed since the initial application of voltage to the coil. For example, as discussed above, when using a 650-ohm coil, a 7V drive rail, and a maximum current of 5mA, a transition of the digital logic line after approximately 8ms indicates that the I / P converter coil and drive circuit are functioning normally, while a transition after approximately 5ms indicates that the armature has not moved, a transition after approximately 1ms indicates that the coil or drive circuit is short-circuited, and no transition at all indicates an open circuit in the coil or drive circuit.

[0023] Now turn to the attached diagram. Figure 1 This is a cross-sectional view of an exemplary electro-pneumatic (I / P) converter 100 (referred to herein as converter 100) constructed according to one or more principles of this disclosure. The exemplary converter 100 converts an electrical input signal into a pneumatic output signal (e.g., a pressure signal) by controlling the flow of pressurized fluid through the converter 100. In some examples, the pneumatic output signal is used to control a device (e.g., a pneumatic actuator for actuating a valve). In some examples, the pneumatic output signal is amplified to a higher pressure and / or volumetric flow rate via a pneumatic relay and then supplied to the actuator to actuate the valve.

[0024] The converter 100 includes a body 102 defining an axial passage 104 extending between a first opening 105 and a second opening 107. The first opening 105 is defined by a supply port 106 to be fluidly coupled to a supply pressure source (e.g., plant air, process gas, etc.). Two output ports 108 are fluidly coupled to the passage 104. The converter 100 operates to block or allow fluid flow between the supply port 106 and the output ports 108. The output ports 108 can be fluidly coupled to a downstream device receiving pressurized fluid, which is considered a pneumatic output signal.

[0025] To control the flow of fluid between the supply port 106 and the output port 108, an exemplary converter 100 includes a solenoid 110 having a coil 112 and a movable armature 114 (e.g., a plug or plunger). The armature 114 is disposed in and movable within a channel 104 between a first opening 105 and a second opening 107. The armature 114 has a first side 116 (e.g., a top side) facing the supply port 106 and a second side 118 (e.g., a bottom side) facing the solenoid 110. The armature 114 can be in a first position (e.g., ... Figure 1 As shown, this position can be referred to as the closed position, the locked position, or the unlocked position, and the second position (such as...). Figure 2 As shown, this position (which may be referred to as an open position, locked position, or open position) moves between two positions. In a first position, armature 114 prevents pressurized fluid from flowing through channel 104 between supply port 106 and output port 108. In a second position, armature 114 allows pressurized fluid to flow through channel 104 between supply port 106 and output port 108, as disclosed in further detail herein. Controller 120 is electrically coupled to coil 112 via drive circuit 121. Controller 120 can activate solenoid 110 by applying current to coil 112 via drive circuit 121, as disclosed in further detail herein.

[0026] The solenoid 110 includes a core 122 and a sleeve 124, with a coil 112 wound around the core 122. The core 122 and the coil 112 are disposed within the sleeve 124. The core 122 has a first side 126 (e.g., a top side) and a second side 128 (e.g., a bottom side) forming the opposite side of the solenoid 110. The solenoid 110 is disposed in a channel 104, near a second opening 107. The solenoid 110 is disposed in a section of the channel 104 having a larger diameter than a section of the channel 104 near the first opening 105. In some examples, the solenoid 110 is press-fitted into the channel 104 through the second opening 107. A seal 130 is disposed between the solenoid 110 and the inner wall 131 of the channel 104. The seal 130 forms a fluid-tight interface between the solenoid 110 and the body 102, and thus prevents fluid flow around the solenoid 110. A first side 133 of the sleeve 124 (e.g., the top side of the solenoid 110) engages with a wall 132 (e.g., a step) of the body 102, which separates the smaller and larger sections of the channel 104. In other examples, the first side 133 of the sleeve 124 may be separable from the wall 132. For example, the solenoid 110 may be formed with a ridge or lip that engages with a corresponding lip formed on the inner wall 131 of the channel (e.g., near the second opening 107), which may be advantageous during manufacturing and / or assembly. The core 122 of the solenoid 110 includes a discharge channel 134 between a first opening 136 (e.g., a discharge port) in a first side 126 of the core 122 and a second opening 138 in a second side 128 of the core 122, as disclosed in further detail herein.

[0027] A stroke stop 140 is disposed in the channel 104, near the supply port 106. The stroke stop 140 has a stroke stop channel 142 between a first opening 144 and a second opening 146. A seal 148 is disposed between the stroke stop 140 and the inner wall 131 of the channel 104 to prevent leakage caused by the stroke stop 140. Therefore, the flow of pressurized fluid into the channel 104 is controlled by the stroke stop channel 142. As discussed further in detail herein, the stroke stop 140 can be adjusted to different positions in the channel 104 to regulate the flow rate when the converter 100 is open or closed. In some examples, the stroke stop 140 is held in the channel 104 by an interference fit. In other examples, the stroke stop 140 can be screwed into the channel 104 by threads. In this example, the stroke stop 140 can be rotated in one direction or the other to adjust its position in the channel 104. Figure 1 As shown, the side of the travel stop 140 facing the armature 114 is conical. However, in other examples, this side of the travel stop 140 may be shaped differently.

[0028] exist Figure 1 In the closed or shut-off position shown, solenoid 110 is not energized, and armature 114 is biased toward supply port 106 via spring 150. Spring 150 is disposed between armature 114 and solenoid 110. The outer portion (e.g., outer circumference) of spring 150 is caught between sleeve 124 (e.g., a notch in the first side 133 of sleeve 124) and wall 132 of body 102. The inner portion (e.g., inner circumference) of spring 150 is coupled to armature 114 at or near the second side 118 of armature 114. The inner portion of spring 150 engages with flange 151 of armature 114 near the second side 118 of armature 114. Spring 150 biases armature 114 toward travel stop 140. Figure 1 In the example shown, spring 150 is a conical tension spring. However, other types of springs can be implemented in other examples. Furthermore, in other examples, spring 150 can be positioned in other locations.

[0029] exist Figure 1 In the closed or shut-off position, armature 114 prevents the flow of fluid from supply port 106. More specifically, armature 114 engages with travel stop 140 and blocks the second opening 146, thereby preventing the flow of fluid through travel stop passage 142. Thus, armature 114 prevents pressurized fluid from flowing through passage 104 between supply port 106 and output port 108. Furthermore, in the closed or shut-off position, armature 114 is spaced apart from the first side 126 of core 122 (e.g., the top side of solenoid 110). In this position, discharge passage 134 fluidly couples passage 104 to the atmosphere. As a result, the flow path is limited between output port 108 and discharge passage 134 (i.e., output port 108 is vented to the atmosphere). Fluid can flow from output port 108, around armature 114 (between armature 114 and inner wall 131 of channel 104), through spring 150, between second side 118 of armature 114 and first side 126 of core 122, and through discharge channel 134 to the atmosphere. Therefore, when converter 100 is in the closed or shut-off position, any positive pressure at output port 108 (and / or fluid lines coupled to output port 108) is released to the atmosphere.

[0030] In order to supply fluid from supply port 106 to output port 108 (e.g., to generate a pneumatic output signal), solenoid 110 can be turned on or activated by applying current to coil 112. Figure 2An exemplary converter 100 is illustrated when the solenoid 110 is activated. The core 122 may be made of an ferrous material (e.g., iron). The current in the coil 112 induces a magnetic field around the core 122. The armature 114, made of a metallic material (e.g., iron), is attracted to the core 122 and moves toward the first side 126 of the core 122. As a result, the armature 114 moves away from the second opening 146 of the travel stop 140, so that pressurized fluid can flow through the channel 104 from the supply port 106 to the output port 108 (as indicated by the arrow). Furthermore, in the open or closed position, the second side 118 of the armature 114 engages with the first side 126 of the core 122. In this position, the armature 114 closes the first opening 136, thereby blocking the discharge channel 134.

[0031] like Figure 1 and Figure 2 As shown, armature 114 can be positioned along axis 152 of channel 104 at a first position blocking supply port 106. Figure 1 ) and the second position of blocking the discharge channel 134 ( Figure 2 The supply port 106 and the discharge channel 134 are axially aligned with channel 104. This geometry allows the armature 114 to move a relatively small distance to control the flow of fluid through the converter 100. In particular, the armature 114 is in the first position ( Figure 1 ) and second position ( Figure 2 The armature 114 moves a relatively small distance between the two channels. In some examples, the armature 114 moves approximately 0.002 inches (in) (0.0508 millimeters (mm)). In other examples, the converter 100 may be designed such that the armature 114 moves more or less within the channel 104.

[0032] like Figure 1 and Figure 2As shown, output port 108 extends from channel 104 in a direction perpendicular to axis 152 of channel 104. In other examples, output port 108 may be oriented at different angles relative to axis 152. Converter 100 includes two output ports 108 disposed on opposite sides of channel 104. In other words, output ports 108 extend from channel 104 in opposite directions. In some examples, by providing two opposing output flow paths, fluid flowing through stroke stop 140 and through armature 114 acts symmetrically on a first side 116 (e.g., top side) of armature 114. In other words, the forces exerted by the fluid flow on the first side 116 of armature 114 are balanced. Otherwise, if only one output port is used, the fluid may bias armature 114 to one side of channel 104, which could cause armature 114 to become misaligned over time. In other examples, converter 100 may include more (e.g., three, four, etc.) or fewer (e.g., one) output ports, and the output ports may be located in other positions and / or oriented in other directions. Figure 1 and Figure 2 In this example, the first side 116 of the armature 114 is relatively flat or planar. As a result, if the armature 114 moves laterally within the channel 104 (towards the inner wall 131), the first side 116 of the armature 114 can still block the second opening 146 of the travel stop 144 when the armature 114 moves back to the first position. In other examples, the first side 116 of the armature can be shaped differently.

[0033] The flow rate of converter 100 can be changed by adjusting the position of travel stop 140 in channel 104. For example, the further travel stop 140 moves toward solenoid 110 into channel 104, the more the armature 114 moves to the second position ( Figure 2 When the travel stop 140 moves away from the solenoid 110 in the channel 104, the space generated between the travel stop 140 and the armature 114 is less. As a result, the flow rate decreases. On the other hand, if the travel stop 140 moves away from the solenoid 110 in the channel 104, when the armature 114 moves to the second position ( Figure 2 When the stroke stop 140 is engaged, more space is created between the stroke stop 140 and the armature 114. As a result, the flow rate increases. Therefore, the exemplary converter 100 can be easily calibrated to achieve the desired flow rate (e.g., corresponding to a pneumatic output signal) by adjusting the position of the stroke stop 140.

[0034] Once the desired pressure is reached at output port 108, controller 120 can deactivate solenoid 110 by stopping the current applied to coil 112, which allows armature 114 to move (e.g., by spring 150) back to the first position. Figure 1This prevents fluid flow to output port 108. Furthermore, discharge passage 134 is opened. As a result, any pressure at output port 108 is discharged to the atmosphere through discharge passage 134. In some examples, controller 120 may apply a reverse current to coil 112, which generates an electromagnetic field in the opposite direction that repels or pushes armature 114 toward travel stop 140. Converter 100 can be activated and deactivated relatively quickly (e.g., via pulses of current) to generate a small pneumatic output signal (e.g., a pulse of air) at output port 108.

[0035] In the closed or closed position ( Figure 1 Armature 114 essentially prevents the flow of pressurized fluid into channel 104. In some cases, only a relatively small amount of fluid leaks into channel 104. In some examples, converter 100 achieves an air consumption of less than 0.1 cubic feet per hour (SCFH) at 20 pounds per square inch (PSI).

[0036] The converter 100 includes a seal 154 (e.g., an O-ring) disposed around the body 102 near the output port 108. The seal 154 can be used to fluidly seal the converter 100 in a hole or channel of the controller.

[0037] In some examples, controller 120 initially applies a higher current to coil 112 to move armature 114 to a second position. Figure 2 The controller 120 then reduces the current to a lower level. Once the armature 114 moves closer to the core 122, less magnetic force is needed to hold the armature 114 in the second position. Therefore, less current is needed to generate a magnetic field sufficient to hold the armature 114 in place. Thus, once the armature 114 has moved to the second position, the controller 120 reduces the current, thereby reducing the total power consumed by the converter 100.

[0038] Figure 3 An exemplary figure 300 is illustrated, showing the applied current (top figure) and corresponding pneumatic output (bottom figure) generated by the exemplary converter 100. As shown, when the converter 100 is turned on, the controller 120 applies a higher current to the coil 112 to move the armature 114 toward the solenoid 110, thereby overcoming the bias of the spring 150. Once the armature 114 moves to the second position ( Figure 2The flow path between supply port 106 and output port 108 is opened, generating a stable pneumatic output pressure. The applied current can then be reduced. As described above, once armature 114 approaches core 122, the attraction between core 122 and armature 114 becomes stronger, thus allowing a lower magnetic field to hold armature 114 in place. In some examples, the higher current is applied only for a short period until armature 114 is located at or near core 122, at which point the current can be reduced. By reducing the current, less energy is used to operate the exemplary converter 100. In particular, the output pressure remains constant even as the current decreases. Therefore, the exemplary converter 100 is more energy-efficient than known converters that apply the same high current throughout activation. In some examples, the high current signal is approximately 3 mA, while the low current signal is approximately 1 mA. The current can then be stopped, causing converter 100 to close and stop generating pneumatic output pressure. Thus, converter 100 operates between three power states (off, high current, and low current) to produce two pneumatic output states (on or off).

[0039] like Figure 2 As shown, when armature 114 is in the second position, the second side 118 of armature 114 engages with the first side 126 of the core. In this position, a pressure differential is formed that biases armature 114 toward solenoid 110 (into the second position). Specifically, the pressure of the fluid in channel 104 acts on the first side 116 (e.g., the top side) and the lateral side of armature 114, thereby forcing armature 114 toward solenoid 110, and the pressure (e.g., atmospheric pressure) in discharge channel 134 acts on a relatively small area on the second side 118 (e.g., the bottom side) of armature 114, thereby forcing armature 114 in the opposite direction. In some cases, if spring 150 does not generate sufficient reaction force on armature 114 to overcome the pressure of the fluid in channel 104 acting on armature 114, armature 114 may remain in the second position even after solenoid 110 is deactivated. In other words, when solenoid 110 is deactivated and armature 104 is in the second position ( Figure 2 When the pressure difference is greater than the combined force of the spring 150 and the pressure in the discharge channel 134 acting on the first side 116 and the lateral side of the armature 104, the armature 114 can be held in the second position by resisting the bias of the spring 150. Therefore, in some examples, a pressure relief mode can be used to allow the higher-pressure air in the channel 104 to act on the second side 118 of the armature 114, so that the pressure acting on all sides of the armature 114 is approximately balanced. This allows the use of a relatively small and lighter spring 150.

[0040] Figure 4 Exemplary graphs 402, 404, and 406 illustrate the changes in voltage applied over time (402), current generated over time (404), and logic line switching over time (406) of an exemplary properly functioning I / P converter. For example, graphs 402 and 404 illustrate the application of a fixed voltage, as shown in graph 402, to a properly functioning I / P converter until a desired maximum current level is reached, as shown in graph 404. The decrease in current shown in graph 404 is initiated by the movement of the armature as the armature's state changes from the closed position to the open position. Then, once the desired maximum current level is reached, the digital logic line switches (as shown in graph 406) and applies a reduced voltage (as shown in graph 402) to hold the armature in the open position. The fact that the logic line switches and the amount of time elapsed from the start of actuation to the logic line switch can be used to diagnose the I / P converter as properly functioning. For example, using a 650-ohm coil, a 7V drive rail, and a maximum current of 5mA, for a normally functioning I / P converter, it will take approximately 8ms from the start of actuation until the maximum current of 5mA is reached.

[0041] Therefore, for I / P converters with these parameters, normal operation can be determined based on the 8ms transition of the digital logic line from the start of actuation. Of course, for I / P converters with different parameters, the amount of time elapsed from actuation to reaching the desired maximum current level can be different. In any case, for I / P converters with known parameters, whether the I / P converter is functioning correctly can be determined based on the amount of time elapsed from the start of actuation when the digital logic line transitions.

[0042] Figure 5 Exemplary graphs 502, 504, and 506 illustrate the variations of applied voltage over time (502), generated current over time (504), and logic line transitions over time (506) for an exemplary I / P converter with an open circuit in the coil or drive circuit. For example, graph 502 illustrates an exemplary I / P converter with an open circuit in the coil or drive circuit where a fixed voltage is applied without limitation, because, as shown in graph 504, the desired maximum current level is never reached. That is, no current is generated due to the open circuit in the coil or drive circuit. Therefore, as shown in graph 506, the logic line never transitions. Thus, an I / P converter can be diagnosed as having an open circuit in the coil or drive circuit based on the fact that the logic line never transitions after a fixed voltage is applied.

[0043] Figure 6Exemplary graphs 602, 604, and 606 illustrate the variation of applied voltage over time (602), generated current over time (604), and logic line transition over time (606) for an exemplary I / P converter with an open circuit in the coil or drive circuit. Due to the elimination of coil impedance, after an initial fixed voltage is applied, the current rises rapidly to reach the desired maximum current, as shown in graph 602, as shown in graph 604. Then, once the desired maximum current level is reached, the digital logic line transitions, as shown in graph 606, and a reduced voltage is applied, as shown in graph 602. The fact that the logic line transition occurs and the amount of time elapsed from the start of actuation to the logic line transition can be used to diagnose the I / P converter as short-circuited. For example, using a shorted coil, a 7V drive rail, and a maximum current of 5mA, approximately 0.1ms will elapse from the start of actuation until the maximum current of 5mA is reached.

[0044] Therefore, for I / P converters with these parameters, a short circuit can be diagnosed based on a digital logic line transition that occurs only 0.1 ms after actuation. Of course, for short-circuit I / P converters with different parameters, the amount of time elapsed from actuation until the desired maximum current level is reached can be different. In any case, for I / P converters with known parameters, a short circuit can be determined based on the amount of time elapsed from the initial applied voltage when the digital logic line transitions. Typically, this amount of time is much shorter than the amount of time it takes for the digital logic line to transition after actuation (which would indicate that the I / P converter is functioning correctly), because the lack of impedance causes the current to reach the desired maximum much faster.

[0045] Figure 7Exemplary graphs 702, 704, and 706 illustrate the variations in applied voltage over time (702), generated current over time (704), and logic line transitions over time (706) for an exemplary I / P converter associated with an armature that is already in the latched (or open) position at actuation or never moves from the unlocked (or closed) position to the latched position. After a fixed voltage is applied, as shown in graph 702, the generated current will reach the desired maximum current level, as shown in graph 704, and the logic line will transition, as shown in graph 706, which transitions faster than a normally functioning I / P converter because there is no drop in current due to armature movement. The I / P converter can be diagnosed as being in the latched position or not moving from the unlocked position to the latched position based on the amount of time elapsed from the start of actuation when the digital logic line transitions. For example, using a 650-ohm coil, a 7V drive rail, and a maximum current of 5mA, in an I / P converter with an armature that is already in the latched position or never moves from the unlocked position to the latched position, it will take approximately 4ms from the start of actuation until the maximum current of 5mA is reached.

[0046] Therefore, for I / P converters with these parameters, it can be determined whether the armature was already in the latched position at the time of actuation, or never moved from the latched position, even after a fixed voltage was applied, based on a 4ms transition of the digital logic line from the start of actuation. Of course, for I / P converters with different parameters and armatures that are either already in the latched position or never moved from the latched position, the amount of time elapsed from the start of actuation until the desired maximum current level is reached can be different. In any case, for I / P converters with known parameters, there exists a timeframe for the digital logic line to transition after actuation begins that indicates whether the I / P converter was in the latched position when a fixed voltage was applied, or whether the I / P converter never moved from the unlocked position to the latched position when a fixed voltage was applied. This timeframe is typically slightly shorter than another timeframe for the digital logic line to transition after actuation begins, which indicates that the I / P converter is functioning normally, since there is no current drop compared to a normally functioning I / P converter (because the armature never actually moves).

[0047] Figure 8 Examples are given for diagnosis. Figure 1 An exemplary logic circuit 800 for a possible failure of an exemplary electric-pneumatic converter. In some examples, the logic shown in circuit 800 may be implemented by a processor of controller 120 (e.g., as a control module), while in other examples, the logic shown in circuit 800 may be implemented by hardware circuit elements of I / P converter 100.

[0048] The timer (T) 802 of logic circuit 800 can determine a fixed voltage (V). 施加 The fixed voltage has been applied to the I / P coil 112 at the first moment. For example, in some examples, when the logic circuit 800 is implemented by the processor of the controller 120, the logic circuit can determine that the fixed voltage has been applied to the I / P coil 112 at the first moment based on the controller 120 causing the fixed voltage to be applied to the I / P coil 112 at the first moment (e.g., via drive circuitry). In other examples, when the logic circuit 800 is implemented by the hardware circuitry elements of the I / P converter 100, the timer 802 can determine that the fixed voltage has been applied to the I / P coil at the first moment based on an indication received from a voltage sensor (not shown) associated with the I / P coil 112, indicating that the fixed voltage has been applied to the I / P coil 112.

[0049] The logic circuit 800 can receive the sensed current level (I0) of the I / P coil 112 from the current sensor 804 associated with the I / P coil 112. 感测 The first comparator (C1) 806 of the logic circuit 800 can compare the sensed current with the expected maximum current level (I) of the I / P coil 112. 最大 The comparison can be made, and the digital logic line 808 can be switched based on the sensed current reaching the desired maximum current level.

[0050] Timer 802 can determine the elapsed time (T) from a first time (when a fixed voltage is applied to I / P coil 112) to a second time associated with a transition of digital logic line 808. 经过 ).

[0051] The second comparator (C2) 810 of the logic circuit 800 can receive the elapsed time from the timer 802 and compare the elapsed time with the expected elapsed time for a normally functioning I / P converter 100 from the time a fixed voltage is applied to the I / P coil 112 to reach the desired maximum current level, in order to determine whether the I / P coil 112 and / or the drive circuit 121 are functioning correctly. Furthermore, if the I / P coil 112 and / or the drive circuit 121 are not functioning correctly, the second comparator 810 can diagnose the possible cause of the fault (diagnostic result).

[0052] For example, if the elapsed time is approximately equal to the expected elapsed time, the second comparator 810 can determine that the I / P converter 100 is functioning normally. If the elapsed time is greater than the expected elapsed time (or if the digital logic line 808 never switches), the second comparator 810 can determine that an open circuit exists in one or more of the I / P coil 112 or the drive circuit 121. If the elapsed time is more than a threshold time less than the expected elapsed time, the second comparator 810 can determine that a short circuit exists in one or more of the I / P coil 112 or the drive circuit 121. Furthermore, if the elapsed time is less than a threshold time less than the expected elapsed time, the second comparator 810 can determine that the armature of the I / P converter 100 was already in the on position when a fixed voltage was applied, or never moved from the off position to the on position.

[0053] In an example where logic circuitry 800 is not implemented as part of controller 120, logic circuitry 800 can send diagnostic results to controller 120. In an example where logic circuitry 800 is implemented as part of controller 120, the controller can directly receive diagnostic results from logic circuitry 800. Controller 120 can then take control actions to change the operation of the process control system based on the diagnostic results. For example, controller 120 can change the control strategy to mitigate the fact that I / P converter 100 is not functioning properly. For example, controller 120 can switch the process control system to a redundant field device based on the fact that I / P converter 100 for a specific field device is not functioning properly. As another example, controller 120 can generate alarms based on diagnostic results, or otherwise transmit diagnostic results to the operator of the process control system.

[0054] Figure 9 This indicates that it can be implemented by controller 120 for diagnosis. Figure 1 A flowchart 900 illustrates an exemplary method for a possible failure of an exemplary electric-pneumatic converter 100.

[0055] At block 902, controller 120 can determine that a fixed voltage has been applied to I / P coil 112 of I / P converter 100 at a first moment (e.g., based on controller 120 applying a fixed voltage to I / P coil 112 via drive circuit 121, and / or based on an indication received from a voltage sensor associated with I / P coil 112 that a fixed voltage has been applied to I / P coil 112).

[0056] At block 904, controller 120 may receive an indication of the sensed current level associated with I / P coil 112, for example, via a current sensor associated with I / P coil 112. At block 906, controller 120 may perform a first comparison, comparing the sensed current level with a desired maximum current level of I / P coil 112. At block 908, when the sensed current level reaches the desired maximum current level of I / P coil 112, controller 120 may cause a digital logic line to switch based on this comparison. At block 910, controller 120 may receive an indication of the time elapsed from a first time to a second time associated with the digital logic line switching. At block 912, controller 120 may perform a second comparison, comparing the time elapsed from the first time to the second time with an expected elapsed time, in which, in a normally functioning I / P converter 100, the digital logic line will switch after a fixed voltage is applied at the expected elapsed time.

[0057] At block 914, controller 120 can determine, based on a second comparison, whether the I / P converter 100 is functioning correctly or whether one or more of the I / P coil 112 or drive circuit 120 has failed. For example, using a 650-ohm coil, a 7V drive rail, and a maximum current of 5mA, approximately 8ms will elapse from actuation until a properly functioning I / P converter reaches its maximum current of 5mA. In this example, controller 120 can compare the time elapsed from the first time to the second time with the expected elapsed time of 8ms. In some examples, controller 120 can determine that the I / P coil and drive circuit are functioning correctly based on the fact that the time elapsed from the first time to the second time is approximately equal to the expected elapsed time. That is, in the example above, if a logic line transition occurs approximately 8ms after a fixed voltage is applied to the I / P coil, controller 120 can determine that the I / P coil and drive circuit are functioning correctly.

[0058] Furthermore, in some examples, the controller 120 can determine that the I / P coil or drive circuit has failed due to an open circuit based on the absence of a logic line transition after a anticipated amount of time has elapsed since the fixed voltage was applied to the I / P coil. That is, when an open circuit exists in the coil or drive circuit, the logic line will never transition because no current is generated. Therefore, if no digital logic line transition occurs before the fixed voltage to the I / P coil is removed, it can be determined that the I / P coil or drive circuit has failed due to an open circuit in the I / P coil or driver.

[0059] Furthermore, in some examples, the controller 120 may determine that one or more of the I / P coil 112 or drive circuit 121 has failed due to a short circuit in one or more of the I / P coil 112 or drive circuit 121 based on the fact that the elapsed time from the first time to the second time is more than a threshold time amount smaller than the expected elapsed time. For example, the threshold time amount may be a specific percentage or fraction of the expected elapsed time (e.g., half of the expected elapsed time, three-quarters of the expected elapsed time, etc.). For example, using a shorted coil, a 7V drive rail, and a maximum current of 5mA, when the coil is short-circuited, the current will rise rapidly because the coil's impedance is eliminated. Therefore, in this example, when the coil is short-circuited, only about 0.1ms elapses from the start of actuation until the 5mA current level is reached, which is much smaller than the expected elapsed time of 8ms for a normally functioning I / P.

[0060] Additionally, in some examples, controller 120 may determine that one or more of the I / P coil 112 or drive circuit 121 have malfunctioned because the armature is already in the on position or because the armature has failed to move from the off position to the on position, based on the fact that the elapsed time from the first time to the second time is less than a threshold time amount that is expected to elapse. For example, as discussed above, the threshold time amount may be a specific percentage or fraction of the expected elapsed time (e.g., half of the expected elapsed time, three-quarters of the expected elapsed time, etc.). That is, in the example above, using a 650-ohm coil, a 7V drive rail, and a maximum current of 5mA, the time to reach the 5mA current level will be reduced when the armature is pulled in or fails to be pulled in at actuation, because the current will not drop (because the armature has not moved). Therefore, in this example, when the armature has not moved, approximately 4ms will elapse from the start of actuation until the 5mA current level is reached, which is approximately half of the expected elapsed time (8ms) for a normally functioning I / P converter 100.

[0061] At block 916, controller 120 can take control actions to alter the operation of the process control system, where I / P converter 100 operates, based on the determination that one or more of I / P coil 112 and / or drive circuit 121 have failed. For example, controller 120 can modify the control strategy to mitigate the fact that I / P converter 100 is not functioning properly. For example, controller 120 can switch the process control system to a redundant field device based on the fact that I / P converter 100 for a specific field device is not functioning properly.

[0062] In addition, in some examples, method 800 may include controller 120 generating an alarm based on determining that one or more of the I / P coils or drive circuits have failed.

[0063] aspect

[0064] Embodiments of the technology described in this disclosure may include any number of the following aspects, individually or in combination:

[0065] 1. A method for diagnosing a fault in a digital solenoid I / P converter in a process control system, wherein the digital solenoid I / P converter includes an I / P coil and a drive circuit, and wherein the digital solenoid I / P converter, when actuated, moves an armature from a closed position to an open position, the method comprising: determining that a fixed voltage has been applied to the I / P coil at a first moment; receiving from a current sensor an indication of a current level associated with the I / P coil; performing a first comparison of the indication of the current level associated with the I / P coil and a desired maximum current level; and, based on the comparison, causing a digital logic line to reach the desired current level associated with the I / P coil. The digital logic line will switch at the maximum current level; receive an indication from the timer of the amount of time elapsed from the first time to the second time, the second time being the time associated with the switching of the digital logic line; perform a second comparison of (i) the amount of time elapsed from the first time to the second time and (ii) the expected amount of time elapsed since the fixed voltage was applied to the I / P coil, after which the digital logic line will switch for a normally functioning I / P coil and drive circuit; and, based on the second comparison, determine whether the I / P coil and the drive circuit are functioning normally or whether one or more of the I / P coil or the drive circuit have failed.

[0066] 2. The method according to aspect 1 further includes: based on determining that one or more of the I / P coil or the drive circuit have failed, causing the controller to take a control action that changes the operation of the process control system.

[0067] 3. The method according to any one of aspect 1 or 2, wherein determining whether the I / P coil and the drive circuit are functioning normally or whether one or more of the I / P coil or the drive circuit have failed further comprises: determining that the I / P coil and the drive circuit are functioning normally based on the amount of time elapsed from the first time to the second time being substantially equal to the expected amount of time elapsed.

[0068] 4. The method according to any one of aspects 1-3, wherein determining whether the I / P coil and the drive circuit are functioning properly or whether one or more of the I / P coil or the drive circuit have failed further comprises: determining that the I / P coil or the drive circuit has failed due to an open circuit in the I / P coil or the drive circuit based on the fact that the digital logic line has not changed after the expected amount of time elapsed from the first time.

[0069] 5. The method according to any one of aspects 1-4, wherein determining whether the I / P coil and the drive circuit are functioning properly or whether one or more of the I / P coil or the drive circuit have failed further comprises: determining that one or more of the I / P coil or the drive circuit has failed due to a short circuit in one or more of the I / P coil or the drive circuit based on the fact that the amount of time elapsed from the first time to the second time is less than the expected amount of time elapsed by more than a threshold time.

[0070] 6. The method according to any one of aspects 1-5, wherein determining whether the I / P coil and the drive circuit are functioning properly or whether one or more of the I / P coil or the drive circuit have failed further comprises: determining that one or more of the I / P coil or the drive circuit have failed because the armature is already in the open position or because the armature has failed to move from the closed position to the open position, based on the amount of time elapsed from the first time to the second time being less than the expected amount of time elapsed by a threshold time amount.

[0071] 7. The method according to any one of aspects 1-6 further includes: generating an alarm based on determining that one or more of the I / P coils or the drive circuits have failed.

[0072] 8. The method according to any one of aspects 1-7, further comprising: removing the fixed voltage applied to the I / P coil after a threshold time period has elapsed since the time the fixed voltage was applied to the I / P coil.

[0073] 9. A system for diagnosing a fault in a digital solenoid I / P converter in a process control system, the system comprising: a digital solenoid I / P converter including an I / P coil and drive circuitry, the digital solenoid I / P converter being configured to move an armature from a closed position to an open position when actuated; a controller configured to apply a fixed voltage to the I / P coil at a first time; a current sensor configured to sense a current quantity associated with the I / P coil; a timer configured to determine an amount of time elapsed from the first time; and a diagnostic circuitry configured to: perform a first comparison of the sensed current quantity associated with the I / P coil with a maximum desired current level; and based on the first comparison, cause a data logic line to... A transition occurs when the sensed current associated with the I / P coil reaches the maximum desired current level; an indication is received from the timer of the amount of time elapsed from the first time to the second time associated with the transition of the digital logic line; a second comparison is performed on (i) the amount of time elapsed from the first time to the second time and (ii) the expected amount of time elapsed since the application of the fixed voltage to the I / P coil, after which a digital logic line transition will occur for a normally functioning I / P coil and drive circuit; and based on the second comparison, it is determined whether the I / P coil and the drive circuit are functioning normally or whether one or more of the I / P coil or the drive circuit have failed.

[0074] 10. The system according to aspect 9, wherein the controller is further configured to: determine, based on a diagnostic circuit, that one or more of the I / P coil or the drive circuit has failed, and take a control action to change the operation of the process control system.

[0075] 11. The system according to any one of aspects 9 or 10, wherein the diagnostic circuit is configured to determine that the I / P coil and the drive circuit are functioning normally based on the amount of time elapsed from the first time to the second time being substantially equal to the expected elapsed time from the application of the fixed voltage to the I / P coil.

[0076] 12. The system according to any one of aspects 9-11, wherein the diagnostic circuit is configured to determine, based on the absence of a logic line transition after the expected elapsed amount of time since the fixed voltage was applied to the I / P coil, that the I / P coil or the drive circuit has failed due to an open circuit in the I / P coil or the drive circuit.

[0077] 13. The system according to any one of aspects 9-12, wherein the diagnostic circuit is configured to determine, based on the fact that the amount of time elapsed from the first time to the second time is more than a threshold amount of time less than the expected amount of time elapsed, that one or more of the I / P coil or the drive circuit has failed due to a short circuit in one or more of the I / P coil or the drive circuit.

[0078] 14. The system according to any one of aspects 9-13, wherein the diagnostic circuit is configured to determine, based on the fact that the amount of time elapsed from the first time to the second time is less than a threshold amount of time than the expected amount of time elapsed, that one or more of the I / P coil or the drive circuit has failed because the armature is already in the open position or because the armature has failed to move from the closed position to the open position.

[0079] 15. The system according to any one of aspects 9-14, wherein the controller is further configured to: generate an alarm based on the diagnostic circuitry determining that one or more of the I / P coils or the drive circuitry have failed.

[0080] 16. The system according to any one of aspects 9-15, wherein the controller is further configured to: remove the fixed voltage applied to the I / P coil after a threshold time period has elapsed since the time the fixed voltage was applied to the I / P coil.

Claims

1. A method for diagnosing faults in digital solenoid I / P converters of field devices in a process control system, wherein, The digital solenoid I / P converter includes an I / P coil and a drive circuit, wherein, when actuated, the digital solenoid I / P converter moves the armature from a closed position to an open position, the method comprising: It is determined that a fixed voltage has been applied to the I / P coil at the first moment; Receive an indication of the current level associated with the I / P coil from the current sensor; Perform a first comparison between the indication of the current level associated with the I / P coil and the expected maximum current level; Based on the first comparison, the digital logic line is made to switch when the current level associated with the I / P coil reaches the desired maximum current level; Receive an indication from the timer of the amount of time that has elapsed from the first time to the second time, the second time being associated with the transition of the digital logic line; A second comparison is performed on (i) the amount of time elapsed from the first time to the second time and (ii) the expected amount of time elapsed from the application of the fixed voltage to the I / P coil. After the expected amount of time elapsed, the digital logic line will switch for a normally functioning I / P coil and drive circuit. Based on the second comparison, it is determined whether the I / P coil and the drive circuit are functioning normally, or whether one or more of the I / P coil or the drive circuit have failed; and Based on the determination that one or more of the I / P coils or the drive circuits have failed, the controller takes a control action to change the operation of the process control system, wherein the control action includes switching from using the field devices in the process control system to using redundant field devices in the process control system.

2. The method according to claim 1, wherein, Determining whether the I / P coil and the drive circuit are functioning properly, or whether one or more of the I / P coil or the drive circuit have failed, also includes: Based on the fact that the amount of time elapsed from the first time to the second time is substantially equal to the expected amount of time elapsed, it is determined that the I / P coil and the drive circuit are functioning normally.

3. The method according to claim 1, wherein, Determining whether the I / P coil and the drive circuit are functioning properly, or whether one or more of the I / P coil or the drive circuit have failed, also includes: Based on the fact that the digital logic line does not jump after the expected amount of time elapsed from the first time, it is determined that the I / P coil or the drive circuit has failed due to an open circuit in the I / P coil or the drive circuit.

4. The method according to claim 1, wherein, Determining whether the I / P coil and the drive circuit are functioning properly, or whether one or more of the I / P coil or the drive circuit have failed, also includes: Based on the fact that the amount of time elapsed from the first time to the second time is more than a threshold amount of time smaller than the expected amount of time elapsed, it is determined that one or more of the I / P coil or the drive circuit has failed due to a short circuit in one or more of the I / P coil or the drive circuit.

5. The method according to claim 1, wherein, Determining whether the I / P coil and the drive circuit are functioning properly, or whether one or more of the I / P coil or the drive circuit have failed, also includes: Based on the fact that the amount of time elapsed from the first time to the second time is less than a threshold amount of time than the expected amount of time elapsed, it is determined that one or more of the I / P coil or the drive circuit have failed because the armature is already in the open position or because the armature has failed to move from the closed position to the open position.

6. The method according to claim 1, further comprising: An alarm is generated based on the determination that one or more of the I / P coils or the drive circuits have failed.

7. The method according to claim 1, further comprising: After a threshold time period has elapsed since the fixed voltage was applied to the I / P coil, the fixed voltage applied to the I / P coil is removed.

8. A system for diagnosing faults in digital solenoid I / P converters in process control systems, the system comprising: The digital solenoid I / P converter of the field device in the process control system includes an I / P coil and a drive circuit. The digital solenoid I / P converter is configured to move the armature from the closed position to the open position when actuated. A controller configured to apply a fixed voltage to the I / P coil at the first moment; A current sensor is configured to sense the amount of current associated with the I / P coil; A timer configured to determine the amount of time that has elapsed since the first time; as well as The diagnostic circuit is configured as follows: Perform a first comparison between the sensed current quantity associated with the I / P coil and the maximum desired current level; Based on the first comparison, the digital logic line is made to switch when the sensed current associated with the I / P coil reaches the maximum desired current level. Receive from the timer an indication of the amount of time elapsed from the first time to the second time associated with the transition of the digital logic line; A second comparison is performed on (i) the amount of time elapsed from the first time to the second time and (ii) the expected amount of time elapsed from the application of the fixed voltage to the I / P coil, after which a digital logic line transition will occur for the normally functioning I / P coil and drive circuit. Based on the second comparison, it is determined whether the I / P coil and the drive circuit are functioning normally or whether one or more of the I / P coil or the drive circuit have failed. as well as Based on the determination that one or more of the I / P coils or the drive circuits have failed, the controller takes a control action to change the operation of the process control system, wherein the control action includes switching from using the field devices in the process control system to using redundant field devices in the process control system.

9. The system according to claim 8, wherein, The diagnostic circuit is configured to determine that the I / P coil and the drive circuit are functioning normally, based on the fact that the amount of time elapsed from the first time to the second time is substantially equal to the expected amount of time elapsed since the fixed voltage was applied to the I / P coil.

10. The system according to claim 8, wherein, The diagnostic circuit is configured to determine, based on the absence of a logic line transition after the expected elapsed amount of time since the fixed voltage was applied to the I / P coil, that the I / P coil or the drive circuit has failed due to an open circuit in the I / P coil or the drive circuit.

11. The system according to claim 8, wherein, The diagnostic circuit is configured to determine, based on the fact that the amount of time elapsed from the first time to the second time is more than a threshold amount of time less than the expected amount of time elapsed, that one or more of the I / P coil or the drive circuit has failed due to a short circuit in one or more of the I / P coil or the drive circuit.

12. The system according to claim 8, wherein, The diagnostic circuit is configured to determine, based on the fact that the amount of time elapsed from the first time to the second time is less than a threshold amount of time than the expected amount of time elapsed, that one or more of the I / P coil or the drive circuit has malfunctioned because the armature is already in the open position or because the armature has failed to move from the closed position to the open position.

13. The system according to claim 8, wherein, The controller is also configured to generate an alarm based on the diagnostic circuitry determining that one or more of the I / P coils or the drive circuitry have failed.

14. The system according to claim 8, wherein, The controller is also configured to remove the fixed voltage applied to the I / P coil after a threshold time period has elapsed since the fixed voltage was applied to the I / P coil.

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