State detection apparatus

A state detection apparatus includes a communication circuit that transmits information to an external apparatus, a control circuit that operates the communication circuit at a first timing, a battery that supplies electric power to the communication and control circuits, and a first explosion-proof barrier connected between a contact circuit and the control circuit. The control circuit applies a test signal, generated based on voltage from the battery, to the contact circuit at a second timing arriving at shorter intervals than the first timing, acquires a detection signal indicating current flow in the contact circuit due to test signal application, and regardless of the first timing, operates the communication circuit when the detection signal is acquired to transmit to the external apparatus that the state of a device connected to the contact circuit is abnormal.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Japanese Patent Application No. 2021-54212 (filed on Mar. 26, 2021), the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a state detection apparatus.

BACKGROUND

Explosion-proof barriers that limit the voltage and current of the operating power supply of a solenoid-type valve in a contact signal converter that converts an on-off contact signal into a control signal for operating the solenoid-type valve are known. See, for example, patent literature (PTL) 1.

CITATION LIST

Patent Literature

SUMMARY

A state detection apparatus according to an embodiment includes a communication circuit, a control circuit, a battery, and a first explosion-proof barrier. The communication circuit transmits information to an external apparatus. The control circuit operates the communication circuit at a first timing. The battery supplies electric power to the communication circuit and the control circuit. The first explosion-proof barrier is connected between the contact circuit and the control circuit. The control circuit applies a test signal, generated based on a voltage outputted by the battery, to the contact circuit via the first explosion-proof barrier at a second timing that arrives at a shorter interval than the first timing. The control circuit acquires, from the first explosion-proof barrier, a detection signal indicating that a current has flowed in the contact circuit due to application of the test signal to the contact circuit. Regardless of the first timing, the control circuit operates the communication circuit at a timing at which the detection signal is acquired to transmit to the external apparatus that a state of a device connected to the contact circuit is an abnormal state.

DETAILED DESCRIPTION

A contact circuit and a state detection apparatus that detects an abnormal state of the contact circuit may be connected via an explosion-proof barrier. When the state detection apparatus transmits the detection result to other devices upon detecting an abnormal state of the contact circuit, it is required that the time between the detection of the abnormal state and the transmission of the detection result be shortened, and also that the power consumption of the communication circuit be reduced. It would be helpful to provide a state detection apparatus that can both shorten the time between detection of an abnormal state and transmission of the detection result and reduce the power consumption of the communication circuit.

A state detection apparatus according to an embodiment includes a communication circuit, a control circuit, a battery, and a first explosion-proof barrier. The communication circuit transmits information to an external apparatus. The control circuit operates the communication circuit at a first timing. The battery supplies electric power to the communication circuit and the control circuit. The first explosion-proof barrier is connected between the contact circuit and the control circuit. The control circuit applies a test signal, generated based on a voltage outputted by the battery, to the contact circuit via the first explosion-proof barrier at a second timing that arrives at a shorter interval than the first timing. The control circuit acquires, from the first explosion-proof barrier, a detection signal indicating that a current has flowed in the contact circuit due to application of the test signal to the contact circuit. Regardless of the first timing, the control circuit operates the communication circuit at a timing at which the detection signal is acquired to transmit to the external apparatus that a state of a device connected to the contact circuit is an abnormal state. With this configuration, the time taken from when the control circuit detects the abnormal state of the contact circuit until the control circuit transmits the detection of the abnormal state to the external apparatus is reduced, regardless of the timing of the detection of the abnormal state of the contact circuit. Furthermore, the time taken from when the control circuit detects the abnormal state of the contact circuit until the control circuit transmits the detection of the abnormal state to the external apparatus is shortened without shortening the interval of the first timing for operating the communication circuit. By the interval of the first timing for operating the communication circuit not being shortened, the power consumption of the communication circuit is reduced. As a result, both the shortening of the time taken from the detection of the abnormal state of the contact circuit by the control circuit to the transmission of the information indicating detection of the abnormal state and the reduction in power consumption of the communication circuit are achieved.

A state detection apparatus according to an embodiment may further include a latch circuit configured to acquire and hold the detection signal. The control circuit may acquire the detection signal from the latch circuit. With this configuration, the control circuit can acquire the detection signal at a timing determined by the control circuit itself. Consequently, the load on the control circuit can be reduced.

In a state detection apparatus according to an embodiment, the control circuit may acquire the detection signal from the latch circuit at a third timing that arrives at a shorter interval than the first timing. With this configuration, the time taken from when the control circuit detects the abnormal state of the contact circuit until the control circuit transmits the detection of the abnormal state to the external apparatus is shortened without shortening the interval of the first timing for operating the communication circuit. As a result, both the shortening of the time taken from the detection of the abnormal state of the contact circuit by the control circuit to the transmission of the information indicating detection of the abnormal state and the reduction in power consumption of the communication circuit are achieved.

In a state detection apparatus according to an embodiment, the control circuit may operate the communication circuit as an interrupt process upon acquiring the detection signal to transmit to the external apparatus that the state of the device connected to the contact circuit is the abnormal state. With this configuration, the time taken from when the control circuit detects the abnormal state of the contact circuit until the control circuit transmits the detection of the abnormal state to the external apparatus is shortened without shortening the interval of the first timing for operating the communication circuit. As a result, both the shortening of the time taken from the detection of the abnormal state of the contact circuit by the control circuit to the transmission of the information indicating detection of the abnormal state and the reduction in power consumption of the communication circuit are achieved.

In a state detection apparatus according to an embodiment, the battery may be a lithium thionyl chloride primary battery. In this way, the state detection apparatus can operate for an extended period of time with a large amount of electric power supplied from the battery. As a result, the state detection apparatus can be used in the field, such as in processing plants and factories, where stable operation for an extended period of time is required.

In a state detection apparatus according to an embodiment, the control circuit may, at the second timing, cause the battery to output a current equal to or greater than a current value based on specifications of the lithium thionyl chloride primary battery. With this configuration, the signal is outputted to the contact circuit in conjunction with an operation to reduce the internal resistance of the battery.

A state detection apparatus according to an embodiment may further include a step-up circuit connected between the first explosion-proof barrier and the contact circuit, and a second explosion-proof barrier connected between the step-up circuit and the contact circuit. The step-up circuit may step up the voltage outputted by the battery to generate a step-up signal and may apply the step-up signal as the test signal to the contact circuit via the second explosion-proof barrier. With this configuration, even if the power outputted from the battery is limited by the first explosion-proof barrier, the voltage inputted to the contact circuit can be stepped up to a level that sufficiently detects the state of the device connected to the contact circuit. Consequently, the state detection apparatus can detect the state of the device connected to the contact circuit.

According to the state detection apparatus of the present disclosure, both a reduction in the time from detection of an abnormal state to transmission of the detection result and a reduction in the power consumption of the communication circuit can be achieved.

Embodiments of the present disclosure are described while being compared to a comparative example.

Comparative Example

As illustrated inFIG.1, a state detection apparatus90according to a comparative example includes a battery91, a control circuit92, a communication circuit93, a switch94, and an explosion-proof barrier95. The state detection apparatus90is connected to a contact circuit96via the explosion-proof barrier95. The contact circuit96is connected to another device. The device connected to the contact circuit96is also referred to as the connected device. The state detection apparatus90can detect the state of the device connected to the contact circuit96by acquiring a signal corresponding to the state of the device connected to the contact circuit96. When the contact circuit96is in the open state (open), the state of the device connected to the contact circuit96is assumed to be normal. When the contact circuit96is in the closed state (conducting state), the state of the device connected to the contact circuit96is assumed to be abnormal.

The battery91supplies electric power to the control circuit92and the communication circuit93. The battery91is connected between a ground point, represented by GND, and a feed point, represented by VCC, and applies voltage to the feed point. The control circuit92controls the operation of the communication circuit93.

The control circuit92controls the switch94to be either open or closed. When the switch94is closed, the voltage applied from the battery91to the feed point is outputted to the contact circuit96via the explosion-proof barrier95.

When a voltage is applied to the contact circuit96via the explosion-proof barrier95, a current corresponding to the state of the device connected to the contact circuit96flows in the contact circuit96. The explosion-proof barrier95outputs a signal based on the detection result of the current flowing in the contact circuit96as a detection signal to the control circuit92. Specifically, when the contact circuit96is closed, i.e., when the state of the device connected to the contact circuit96is abnormal, the explosion-proof barrier95detects the flow of current in the contact circuit96. The explosion-proof barrier95outputs a signal indicating that a current has flowed in the contact circuit96as a detection signal. On the other hand, when the contact circuit96is open, i.e., when the state of the device connected to the contact circuit96is normal, the explosion-proof barrier95detects that no current has flowed in the contact circuit96. In the case of detecting that no current has flowed in the contact circuit96, the explosion-proof barrier95does not output a detection signal.

In the case in which the control circuit92acquires a detection signal, which is a signal corresponding to the state of the device connected to the contact circuit96, from the explosion-proof barrier95when the switch94is closed, the control circuit92determines that the state of the device connected to the contact circuit96is abnormal based on the detection signal. In the case in which the control circuit92does not acquire a detection signal, which is a signal corresponding to the state of the device connected to the contact circuit96, from the explosion-proof barrier95when the switch94is closed, the control circuit92determines that the state of the device connected to the contact circuit96is normal based on the non-acquisition of the detection signal.

In the case of determining that the state of the device connected to the contact circuit96is abnormal, the control circuit92uses the communication circuit93to transmit, to an external apparatus, an indication that the state of the device connected to the contact circuit96is abnormal.

Here, to reduce the power consumption of the communication circuit93and delay the draining of the battery91, the control circuit92controls the communication circuit93to be in a non-operating state, such as suspended or asleep, as a general rule and controls the communication circuit93to operate in a first cycle.

For frequent checking of the state of the device connected to the contact circuit96while delaying the draining of the battery91, the control circuit92controls the switch94to be open as a general rule and controls the switch94to be closed in the first cycle and in a second cycle that is shorter than the first cycle.

The operating condition of the communication circuit93and the state of the switch94are illustrated as a timing chart inFIG.2for the case in which the control circuit92controls the communication circuit93and the switch94in the first and second cycles. InFIG.2, the horizontal axis represents the passage of time. In the row for the switch94, two dashed lines corresponding to the state of the switch94being “ON” or “OFF” are depicted. The solid line superimposed on the dashed lines represents which of the two states, “ON” or “OFF”, the state of the switch94changes to as time passes. In the period in which the solid line is superimposed on the dashed line on the “ON” side, the switch94is closed. In the period in which the solid line is superimposed on the dashed line on the “OFF” side, the switch94is open. The second cycle over which the control circuit92controls the state of the switch94to be “ON” is represented by T2.

In the row for the communication circuit93, two dashed lines corresponding to the operating condition of the communication circuit93being “ON” or “OFF” are depicted. The solid line superimposed on the dashed lines represents which of the two operating conditions, “ON” or “OFF”, the operating condition of the communication circuit93changes to as time passes. In the period in which the solid line is superimposed on the dashed line on the “ON” side, the communication circuit93is operating. In the period in which the solid line is superimposed on the dashed line on the “OFF” side, the communication circuit93is not operating. The first cycle over which the control circuit92operates the communication circuit93is represented by T1.

As described above, the control circuit92can acquire a detection signal from the explosion-proof barrier95when a current flows in the contact circuit96due to closing of the switch94. Upon acquiring the detection signal, the control circuit92can confirm that the state of the device connected to the contact circuit96is abnormal. An example of a detection signal is illustrated in the timing chart inFIG.2. In the row for the detection signal, two dashed lines corresponding to the state of the detection signal being “ON” or “OFF” are depicted. The solid line superimposed on the dashed lines represents which of the two states, “ON” or “OFF”, the detection signal changes to as time passes. In the period in which the solid line is superimposed on the dashed line on the “ON” side, the detection signal is being outputted from the explosion-proof barrier95. In the period in which the solid line is superimposed on the dashed line on the “OFF” side, the detection signal is not being outputted from the explosion-proof barrier95.

Here, in the timing chart ofFIG.2, the control circuit92detects that the state of the detection signal is “ON” at the timing represented as XC by a vertical dashed dotted line, i.e., that the detection signal has been outputted from the explosion-proof barrier95. Based on the state of the detection signal having changed to “ON”, the control circuit92determines that the state of the device connected to the contact circuit96is abnormal. After determining that the state of the device connected to the contact circuit96is abnormal, the control circuit92operates the communication circuit93at the timing that arrives next in the first cycle, represented as RC by a vertical dashed dotted line, and uses the communication circuit93to transmit to an external apparatus an indication that the state of the device connected to the contact circuit96is abnormal.

As a result of the control circuit92operating the communication circuit93in the first cycle, the time taken from when the control circuit92detects the abnormal state of the contact circuit96until the control circuit92transmits the detection of the abnormal state to the external apparatus depends on the timing of the detection of the abnormal state of the contact circuit96. The time taken from the detection to transmission of the abnormal state of the contact circuit96by the control circuit92is also referred to as the delay time and is represented by D inFIG.2.

The control circuit92may shorten the first cycle to shorten the delay time regardless of the timing of the detection of the abnormal state of the device connected to the contact circuit96. However, shortening the first cycle increases the operation frequency of the communication circuit93, which consumes a large amount of power, and causes an increase in the power consumption of the state detection apparatus90as a whole. Consequently, the battery91will be drained faster.

As described above, the state detection apparatus90according to the comparative example is problematic since it is difficult to shorten the delay time from detection to transmission of the abnormal state of the contact circuit96while delaying the draining of the battery91by lengthening the operation cycle of the communication circuit93.

The present disclosure therefore describes a state detection apparatus1(seeFIG.3) that can reduce the delay time from detection to transmission of an abnormal state of a contact circuit30(seeFIG.3) while delaying the draining of a battery11(seeFIG.3). The state detection apparatus1may be applied to edge computer gateways. The state detection apparatus1may also be used in a gateway terminal for the Internet of Things (IoT).

Embodiment of the Present Disclosure

As illustrated inFIG.3, the state detection apparatus1according to an embodiment includes a transmitter10and a signal converter20. The transmitter10incudes a battery11, a control circuit12, a switch14, an explosion-proof barrier15, a communication circuit16, and a latch circuit17. The signal converter20includes a step-up circuit21and an explosion-proof barrier24. The state detection apparatus1is connected to a contact circuit30via the explosion-proof barrier24of the signal converter20. In other words, the explosion-proof barrier24is connected between the signal converter20and the contact circuit30. The explosion-proof barrier15is connected between the control circuit12and the contact circuit30. The explosion-proof barrier15is also referred to as the first explosion-proof barrier. The explosion-proof barrier24is also referred to as the second explosion-proof barrier.

The explosion-proof barrier15or24includes Zener diodes ZD1and ZD2connected in parallel between a signal line L1and a ground line L2, and a resistor R1is connected in series with the signal line L1, as illustrated inFIG.4, for example. The signal line L1connects the battery11and the contact circuit30. The resistor R1is connected in series on the side connected to the contact circuit30. The explosion-proof barrier24further includes a current detection circuit that detects the current flowing in the contact circuit30. The current detection circuit may, for example, include a light emitting diode that emits light when a current flows in the contact circuit30and a light detecting element that detects the emission of the light emitting diode. The light detecting element outputs a signal indicating detection of light emission when a current flows in the contact circuit30. The signal indicating detection of light emission corresponds to a signal indicating that a current has flowed in the contact circuit30.

The Zener diodes ZD1, ZD2limit the voltage applied to the signal line L1. The Zener diode ZD1or ZD2may be configured by a plurality of Zener diodes connected in series. The signal propagates from the battery11towards the contact circuit30. As a result of the resistor R1being connected downstream in the signal propagation direction of the signal line L1, the voltage outputted by the explosion-proof barrier15or24is limited by the maximum voltage applied to the Zener diodes ZD1, ZD2.

The resistor R1limits the current outputted from the explosion-proof barrier15or24. The resistance of the resistor R1is determined based on the upper limit of the voltage determined by the Zener diodes ZD1, ZD2and the upper limit of the current to be determined by the resistor R1.

The state detection apparatus1outputs a test signal, generated based on the voltage outputted by the battery11, to the contact circuit30from the battery11of the transmitter10via the switch14, the explosion-proof barrier15, the step-up circuit21, and the explosion-proof barrier24. The contact circuit30is connected to another device. The device connected to the contact circuit30is also referred to as the connected device. When the test signal is applied to the contact circuit30from the state detection apparatus1, a current flows in the contact circuit30according to the state of the device connected to the contact circuit30. When the contact circuit30is in the open state (open), the state of the device connected to the contact circuit30is assumed to be normal. When the contact circuit30is in the closed state (conducting state), the state of the device connected to the contact circuit30is assumed to be abnormal. When detecting that a current has flowed in the contact circuit30, the explosion-proof barrier24of the signal converter20outputs a signal indicating that a current has flowed in the contact circuit30. The signal indicating that a current has flowed in the contact circuit30is also referred to as a detection signal. The transmitter10of the state detection apparatus1acquires the detection signal from the explosion-proof barrier24and can thereby detect that the state of the device connected to the contact circuit30is abnormal.

The battery11supplies electric power to the control circuit12and the communication circuit16. The battery11is connected between a ground point, represented by GND, and a feed point, represented by VCC, and applies voltage to the feed point. The control circuit12controls the operation of the communication circuit16.

The control circuit12controls the switch14to be either open or closed. When the switch14is closed, the voltage applied from the battery11to the feed point is outputted to the signal converter20via the explosion-proof barrier15.

The step-up circuit21of the signal converter20outputs a step-up signal, yielded by stepping up the voltage applied from the battery11via the switch14and the explosion-proof barrier15, as a test signal to the contact circuit30via the explosion-proof barrier24. The step-up circuit21may be configured as a chopper circuit that includes a capacitor, inductor, or the like, to step up the voltage outputted by the battery11. Although the power inputted to the step-up circuit21from the transmitter10is limited by the explosion-proof barrier15, the voltage inputted to the contact circuit30can be stepped up enough to detect the state of the device connected to the contact circuit30by a large-capacity capacitor or inductor being mounted in the step-up circuit21.

When a step-up signal is inputted to the contact circuit30from the explosion-proof barrier24of the signal converter20, a current corresponding to the state of the device connected to the contact circuit30flows in the contact circuit30. The explosion-proof barrier24outputs a detection signal based on the detection result of the current flowing in the contact circuit30to the transmitter10. Specifically, when the contact circuit30is closed, i.e., when the state of the device connected to the contact circuit30is abnormal, the explosion-proof barrier24detects the flow of current in the contact circuit30. The explosion-proof barrier24outputs a detection signal to the transmitter10indicating that a current has flowed in the contact circuit30. The voltage of the detection signal may be the same as or lower than the voltage of the step-up signal. In other words, the voltage of the detection signal may be equal to or less than the voltage of the step-up signal. On the other hand, when the contact circuit30is open, i.e., when the state of the device connected to the contact circuit30is normal, the explosion-proof barrier24detects that no current has flowed in the contact circuit30. In the case of detecting that no current has flowed in the contact circuit30, the explosion-proof barrier24does not output a detection signal to the transmitter10.

When the explosion-proof barrier24of the signal converter20outputs the detection signal to the transmitter10, the detection signal is inputted to the latch circuit17via the explosion-proof barrier15of the transmitter10. The latch circuit17holds the inputted detection signal. The control circuit12acquires the detection signal held in the latch circuit17. The control circuit12may accept the input of the detection signal from the latch circuit17when the latch circuit17holds the detection signal. The control circuit12may acquire the detection signal from the latch circuit17at a timing determined by the control circuit12itself after the latch circuit17holds the detection signal. The control circuit12may, for example, acquire the detection signal from the latch circuit17at the next timing for controlling the switch14to be closed.

In a case in which the detection signal is acquired, the control circuit12can determine that the state of the device connected to the contact circuit30is abnormal. In a case in which the detection signal is not acquired, the control circuit12can determine that the state of the device connected to the contact circuit30is normal. In other words, the control circuit12can determine that the state of the device connected to the contact circuit30is abnormal in the case in which the detection signal, which is a signal corresponding to the state of the device connected to the contact circuit30, is acquired when the switch14is closed.

In the case of determining that the state of the device connected to the contact circuit30is abnormal, the control circuit12uses the communication circuit16to transmit, to an external apparatus, an indication that the state of the device connected to the contact circuit30is abnormal.

Here, to reduce the power consumption of the communication circuit16and delay the draining of the battery11, the control circuit12controls the communication circuit16to be in a non-operating state, such as suspended or asleep, as a general rule and controls the communication circuit16to operate at a first timing. The first timing may be a timing that arrives periodically or at irregular intervals. In the present embodiment, the first timing arrives in a first cycle.

For frequent checking of the state of the device connected to the contact circuit30while delaying the draining of the battery11, the control circuit12controls the switch14to be open as a general rule and controls the switch14to be closed at a second timing that arrives at shorter intervals than the first timing. In the present embodiment, the second timing arrives in a second cycle shorter than the first cycle.

The operating condition of the communication circuit16and the state of the switch14are illustrated as a timing chart inFIG.5for the case in which the control circuit12controls the communication circuit16and the switch14at the first and second timings. InFIG.5, the horizontal axis represents the passage of time. In the row for the switch14, two dashed lines corresponding to the state of the switch14being “ON” or “OFF” are depicted. The solid line superimposed on the dashed lines represents which of the two states, “ON” or “OFF”, the state of the switch14changes to as time passes. In the period in which the solid line is superimposed on the dashed line on the “ON” side, the switch14is closed. In the period in which the solid line is superimposed on the dashed line on the “OFF” side, the switch14is open. The second cycle over which the control circuit12controls the state of the switch14to be “ON” is represented by T2.

In the row for the communication circuit16, two dashed lines corresponding to the operating condition of the communication circuit16being “ON” or “OFF” are depicted. The solid line superimposed on the dashed lines represents which of the two operating conditions, “ON” or “OFF”, the operating condition of the communication circuit16changes to as time passes. In the period in which the solid line is superimposed on the dashed line on the “ON” side, the communication circuit16is operating. In the period in which the solid line is superimposed on the dashed line on the “OFF” side, the communication circuit16is not operating. The first cycle over which the control circuit12operates the communication circuit16is represented by T1.

As described above, the control circuit12inputs the test signal, generated by the voltage outputted by the battery11due to the switch14being closed, to the signal converter20. The signal converter20applies the voltage of the test signal to the contact circuit30via the explosion-proof barrier24. When the state of the device connected to the contact circuit30is abnormal, the application of the test signal to the contact circuit30causes a current to flow in the contact circuit30. In the case of detecting that a current has flowed in the contact circuit30, the explosion-proof barrier24outputs a detection signal. The control circuit12acquires the detection signal from the explosion-proof barrier24of the signal converter20. The control circuit12can check the state of the device connected to the contact circuit30based on the acquired detection signal. An example of a detection signal is illustrated in the timing chart inFIG.5. In the row for the detection signal, two dashed lines corresponding to the state of the detection signal being “ON” or “OFF” are depicted. The solid line superimposed on the dashed lines represents which of the two states, “ON” or “OFF”, the detection signal changes to as time passes. In the period in which the solid line is superimposed on the dashed line on the “ON” side, the explosion-proof barrier24is outputting the detection signal. In the period in which the solid line is superimposed on the dashed line on the “OFF” side, the explosion-proof barrier24is not outputting the detection signal.

Here, in the timing chart ofFIG.5, the control circuit12detects that the state of the detection signal is “ON”, i.e., that the detection signal has been outputted from the explosion-proof barrier24, at the timing represented as X by a vertical dashed dotted line. Based on the state of the detection signal having changed to “ON”, the control circuit12determines that the state of the device connected to the contact circuit30is abnormal. After determining that the state of the device connected to the contact circuit30is abnormal, the control circuit12operates the communication circuit16at a special timing represented as Y by a vertical dashed dotted line, without waiting until the arrival of the next first timing represented as R by a vertical dashed dotted line, to transmit to the external apparatus, using the communication circuit16, an indication that the state of the device connected to the contact circuit30is abnormal.

As a result of the control circuit12operating the communication circuit16at the special timing (Y) after acquiring the detection signal, the time taken from when the control circuit12detects the abnormal state of the contact circuit30until the control circuit12transmits the detection of the abnormal state to the external apparatus is shortened, regardless of the timing of the detection of the abnormal state of the contact circuit30.

As described above, in the state detection apparatus1of the present embodiment, the control circuit12operates the communication circuit16at the first timing and operates the communication circuit16at a special timing when a detection signal is acquired. With this configuration, the time taken from when the control circuit12detects the abnormal state of the contact circuit30until the control circuit12transmits the detection of the abnormal state to the external apparatus is shortened, regardless of the timing of the detection of the abnormal state of the contact circuit30. Furthermore, the time taken from when the control circuit12detects the abnormal state of the contact circuit30until the control circuit12transmits the detection of the abnormal state to the external apparatus is shortened without shortening the interval of the first timing for operating the communication circuit16. By the interval of the first timing for operating the communication circuit16not being shortened, the power consumption of the communication circuit16is reduced. As a result, both the shortening of the time taken from the detection of the abnormal state of the contact circuit30by the control circuit12to the transmission of the information indicating detection of the abnormal state and the reduction in power consumption of the communication circuit16are achieved.

In addition, by including the explosion-proof barrier15or24, the state detection apparatus1can be used as equipment with an intrinsically safe explosion-proof structure to monitor the state of the device connected to the contact circuit30.

The state detection apparatus1also includes the explosion-proof barrier24between the signal converter20, which includes the step-up circuit21, and the contact circuit30. The step-up signal is therefore not inputted to the transmitter10even when the voltage of the detection signal is lower than the voltage of the step-up signal.

The state detection apparatus1also includes the step-up circuit21in the signal converter20, so that even if the power outputted from the transmitter10is limited by the explosion-proof barrier15, the voltage inputted to the contact circuit30can be sufficiently stepped up to detect the state of the device connected to the contact circuit30.

OTHER EMBODIMENTS

The transmitter10of the state detection apparatus1need not include the latch circuit17. In this case, the control circuit12acquires the detection signal from the explosion-proof barrier24of the signal converter20when the detection signal is inputted. The control circuit12may operate the communication circuit16upon acquiring the detection signal. By the transmitter10not including the latch circuit17, a reduction in the size or cost of the circuitry for the transmitter10can be achieved. Upon acquiring the detection signal, the control circuit12may execute a process to operate the communication circuit16as an interrupt process and transmit the detection of an abnormal state of the contact circuit30to the external apparatus.

As a result of the state detection apparatus1including the latch circuit17on the line that inputs the detection signal from the signal converter20to the control circuit12, the control circuit12can acquire the detection signal at a timing determined by the control circuit12itself. The control circuit12may set a third timing, which arrives at a shorter interval than the first timing, as the timing for acquiring the detection signal from the latch circuit17. In the case in which the control circuit12operates the communication circuit16when the detection signal is inputted to the control circuit12, the control circuit12needs to implement an interrupt process in response to input of the detection signal. The interrupt process may place a heavy load on the control circuit12and increase the circuit size of the control circuit12. Therefore, the load on the control circuit12can be reduced by enabling the control circuit12to acquire the detection signal at a timing determined by the control circuit12itself.

The latch circuit17may be included in the control circuit12. For example, the control circuit12may include a memory, such as a non-volatile memory, that holds the detection signal. In this way, a reduction in the size or cost of circuitry can be achieved.

The battery11may be a lithium thionyl chloride primary battery.

Lithium thionyl chloride primary batteries are characterized by high power capacity and low self-discharge, allowing these batteries to be used for an extended period of time. Therefore, lithium thionyl chloride primary batteries are sometimes incorporated into wireless measurement apparatuses used in the field, such as process plants and factories, where stable operation over an extended period of time is required.

During the use of a lithium thionyl chloride primary battery, a rise in internal resistance due to the formation of a chloride film inside the lithium thionyl chloride primary battery may become problematic when the load current flowing in the lithium thionyl chloride primary battery is small. Specifically, once the internal resistance of the lithium thionyl chloride primary battery has increased due to a prolonged period of low load current, an apparatus that operates on power from the lithium thionyl chloride primary battery may suddenly transition to high load operation. In this case, the current flowing in the lithium thionyl chloride primary battery suddenly increases. The increase in current in a state of increased internal resistance causes a sudden drop in output voltage. The drop in output voltage may cause the apparatus to stop or cause abnormal operation of the apparatus.

Therefore, an apparatus using a lithium thionyl chloride primary battery monitors the internal resistance of the lithium thionyl chloride primary battery, and in a case in which the internal resistance reaches a predetermined value or greater, the apparatus executes an operation to reduce the internal resistance. Specifically, in a case in which the internal resistance reaches a predetermined value or greater, the internal resistance is reduced by application of a current equal to or greater than a predetermined current to the lithium thionyl chloride primary battery. The predetermined current may be a current value determined based on the specifications of the lithium thionyl chloride primary battery.

In the case in which the battery11is a lithium thionyl chloride primary battery in the state detection apparatus1of the present embodiment, the control circuit12can reduce the internal resistance of the battery11by applying a current equal to or greater than the predetermined current. The transmitter10further includes a load circuit13, as illustrated inFIG.3, although this component is not essential. The load circuit13is configured to include a load such as electrical resistance. In the case in which the transmitter10includes the load circuit13, the control circuit12may apply current to the load circuit13so as to apply a current equal to or greater than the predetermined current to the battery11.

The control circuit12may output a signal to the contact circuit30in conjunction with performing the operation to reduce the internal resistance of the lithium thionyl chloride primary battery. In this case, the control circuit12may control the switch14to be closed so that a portion of the current flowing to the battery11flows to the signal converter20. In other words, the first timing may be the timing at which the internal resistance of the battery11becomes a predetermined value or greater.

The signal converter20of the state detection apparatus1need not include the step-up circuit21. In this case, the signal converter20inputs a voltage signal having the voltage outputted by the battery11as a test signal to the contact circuit30.

The state detection apparatus1according to the present embodiment can be applied to devices that operate with small power consumption in a normal state and operate with greater power consumption than normal in an abnormal state.

In a case in which the state detection apparatus1does not include the signal converter20, a test signal may be applied from the explosion-proof barrier15to the contact circuit30. In this case, the explosion-proof barrier15includes a current detection circuit that detects the current flowing in the contact circuit30. The explosion-proof barrier15detects the current flowing in the contact circuit30and outputs a detection signal to the control circuit12indicating that a current has flowed in the contact circuit30. The current detection circuit of the explosion-proof barrier15may have a configuration that is the same as or similar to the configuration described for the current detection circuit of the explosion-proof barrier24.

Although embodiments of the present disclosure have been described through drawings and examples, it is to be noted that various changes and modifications will be apparent to those skilled in the art on the basis of the present disclosure. Therefore, such changes and modifications are to be understood as included within the scope of the present disclosure. For example, the functions or the like included in the various components or steps may be reordered in any logically consistent way. Furthermore, components or steps may be combined into one or divided.