JP2013228265A - Temperature detector and abnormality determination method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature detector that can detect ground potential short circuit abnormality of a thermocouple as well as disconnection abnormality of the thermocouple and can perform temperature detection even though the temperature detector has a single power source structure, and further to provide an abnormality determination method for such temperature detector.SOLUTION: In a temperature detector 1, a controller 21 for executing a step S180 determines whether or not disconnection abnormality in a thermocouple 3 is present on the basis of comparison results between a temperature detection signal St and a disconnection abnormality determination value Th3 in a state that a second inputting section 33 and a ground 49 are set to a current-carrying state by a ground potential switching section 17. Further, the controller 21 for executing a step S140 or a step S170 determines whether or not ground potential short circuit abnormality in the thermocouple 3 is present on the basis of comparison results between an input side set potential Vcs and a ground potential short circuit abnormality determination value Th2.

Description

  The present invention relates to a temperature detection device that detects a temperature using a thermocouple and an abnormality determination method for a temperature detection device that detects a temperature using a thermocouple.

Conventionally, a temperature detection device using a thermocouple is known as a temperature detection device in automobiles, home appliances, industrial equipment, medical equipment, and other electrical equipment.
Here, since the electromotive force generated in the thermocouple according to the detection target temperature is weak and the voltage at both ends generated at the two output ends of the thermocouple is small according to the detection target temperature, the thermocouple is used. In a conventional temperature detection device, for example, the voltage across the thermocouple is amplified by an amplifier circuit such as an operational amplifier.

  The temperature detection device using a thermocouple detects the temperature based on the voltage across the two output terminals of the thermocouple. However, if the thermocouple breaks for some reason, the temperature detection is performed appropriately. It may not be possible.

For this reason, some temperature detection devices using thermocouples have a function of determining the presence or absence of a disconnection abnormality of a thermocouple.
As a method for determining the presence or absence of a disconnection abnormality of a thermocouple, for example, a disconnection determination current is supplied to the thermocouple, and whether or not there is a disconnection abnormality is determined based on whether or not the voltage across the thermocouple indicates a normal range. There is a method of determination (Patent Documents 1 and 2).

  Thus, in order to supply the disconnection determination current to the thermocouple, it is necessary to set one of the two output ends of the thermocouple to a specific potential, and thus one of the two output ends of the thermocouple. A configuration is adopted in which is connected to the ground.

  When a disconnection determination current is applied to the thermocouple, the voltage at both ends of the thermocouple fluctuates due to the influence of the disconnection determination current, so that the temperature detection accuracy may be reduced. Therefore, by setting the temperature detection period and the disconnection determination period in different time zones, it is possible to prevent a decrease in temperature detection accuracy.

  By the way, as a temperature detection element (temperature sensor element), in addition to a thermocouple, a thermistor is known. However, a thermocouple generates an electromotive force according to temperature, whereas a thermistor does not generate an electromotive force but has a characteristic that an electric resistance value changes according to temperature. For this reason, the temperature detection apparatus using a thermistor is the structure which detects the electrical resistance value of a thermistor by the electricity supply to a thermistor from the outside, and detects temperature based on the electrical resistance value (patent document 3).

  That is, a temperature detection device using a thermocouple has a different principle regarding temperature detection and a completely different configuration as compared with a temperature detection device using a thermistor.

Japanese Utility Model Publication No. 02-124526 Japanese Patent No. 2516700 JP 2005-009924 A

  However, in the configuration in which one of the two output ends of the thermocouple is connected to the ground, it is possible to determine whether or not the thermocouple is disconnected, but there is a problem that the ground potential short-circuit abnormality of the thermocouple cannot be detected.

  That is, in the configuration in which one of the thermocouple output terminals is connected to the ground, even if a ground potential short circuit abnormality of the thermocouple occurs, the both-end voltages generated at the two output terminals of the thermocouple are Since it is equal to the voltage across the thermocouple, it is difficult to determine whether or not a ground potential short-circuit abnormality has occurred in the thermocouple.

  In addition, when the temperature detection device is configured to be driven by a single power source and one of the two output ends of the thermocouple is connected to the ground, the other end of the thermocouple is lower than the ground potential. Temperature detection is impossible for the temperature range where the potential is reached.

  That is, in a temperature detection device driven by a single power source, a signal amplification unit (such as an operational amplifier) provided therein cannot amplify a potential lower than the ground potential. For this reason, for example, when one end of the thermocouple is connected to the ground and the voltage across the thermocouple becomes a voltage corresponding to a negative temperature, the other end of the thermocouple becomes a potential lower than the ground potential. Under such circumstances, amplification by the signal amplifying unit is impossible, and thus temperature detection cannot be performed in a temperature range in which the voltage across the thermocouple is a voltage corresponding to a negative temperature.

  In order to detect the “voltage corresponding to the negative temperature” of the thermocouple, for example, there is a method of providing a plurality of power supplies. In other words, by providing a plurality of power supplies so that power can be supplied from the power supply even in a potential range lower than the ground potential, signal amplification by the signal amplification unit even when the voltage across the thermocouple becomes a voltage corresponding to a negative temperature Is possible.

However, when a plurality of power supplies are provided, there is a problem that the configuration of the temperature detection device is complicated.
As described above, a temperature detection device using a thermistor instead of a thermocouple is completely different from a temperature detection device using a thermocouple, and is therefore used in a temperature detection device using a thermistor. Various configurations (such as a thermistor abnormality determination configuration) are difficult to apply to a temperature detector using a thermocouple.

  Therefore, the present invention can detect not only the disconnection abnormality of the thermocouple but also at least one of the ground potential short-circuit abnormality and the other-potential short-circuit abnormality of the thermocouple, and the voltage across the thermocouple is negative even in a single power supply configuration. The purpose of the present invention is to provide a temperature detection device that can detect a temperature in a temperature range that corresponds to the temperature, and that can detect not only a thermocouple disconnection abnormality but also a thermocouple ground potential short-circuit abnormality. An object of the present invention is to provide a method for determining an abnormality.

  The present invention is a temperature detection device that detects a temperature based on a potential difference between two output ends of a thermocouple, and includes a first input portion and a second input portion that are electrically connected to the two output ends of the thermocouple. And a signal amplifying unit that amplifies the potential difference generated between the first input unit and the second input unit and outputs the amplified signal as a temperature detection signal.

  The temperature detecting device includes an input reference potential setting unit that sets the potential of the first input unit in the signal input unit to an input reference potential that is higher than the ground potential of the ground, and the electrical connection between the second input unit and the ground. And a ground potential switching unit that switches a normal connection state to an energized state or a disconnected state.

  Further, the temperature detection device compares the temperature detection signal with a predetermined disconnection abnormality determination value in a state where the second input unit and the ground are set to the energized state by the ground potential switching unit, and the comparison result is Based on the result of the comparison, the potential of the first input unit and the input reference potential are compared, and the ground potential short-circuit abnormality and other potential short-circuit in the thermocouple are determined. A short-circuit abnormality determining unit that determines the presence or absence of at least one abnormality.

  In the temperature detection device having such a configuration, the input reference potential setting unit sets the potential of the first input unit to the input reference potential, so that the “reference potential of the voltage across the thermocouple” in the signal amplification unit is the ground potential. Higher potential (input reference potential).

  As a result, even if the voltage across the thermocouple is a voltage corresponding to the negative temperature, each potential at the “two output terminals of the thermocouple” input to the signal amplifier is within the ground potential. In, the signal amplifier can amplify the voltage across the thermocouple (the voltage corresponding to the negative temperature). That is, by providing the input reference potential setting unit, even in a single power supply configuration, temperature detection in a temperature range in which the voltage across the thermocouple becomes a voltage corresponding to a negative temperature is possible.

  In addition, by providing the ground potential switching unit, the electrical connection state between the second input unit and the ground can be switched to the energized state or the cut-off state. For this reason, when determining the presence or absence of a disconnection abnormality in the thermocouple, the ground potential switching unit sets the second input unit and the ground to the energized state and does not determine the presence or absence of a disconnection abnormality (in other words, the temperature In the case of detection), the ground potential switching unit can set the second input unit and the ground to a cut-off state.

  Therefore, a disconnection abnormality determination value for determining whether there is a disconnection abnormality is determined in advance, and the temperature detection signal and the disconnection abnormality are set in a state where the second input unit and the ground are set to the energized state by the ground potential switching unit. By comparing with the determination value, it is possible to determine whether there is a disconnection abnormality. Therefore, the disconnection abnormality determination unit compares the temperature detection signal with the disconnection abnormality determination value in a state where the second input unit and the ground are set to the energized state by the ground potential switching unit, and based on the comparison result. The presence or absence of disconnection abnormality in the thermocouple can be determined.

  On the other hand, since the electromotive force of the thermocouple is weak, when the ground potential short-circuit abnormality or other-potential short-circuit abnormality (such as short-circuit to the power supply positive electrode potential) occurs in the thermocouple, the first input unit and the second input unit These potentials are substantially equal to the ground potential or other potentials, and it becomes difficult for the input reference potential setting unit to set the potential of the first input unit to the input reference potential. That is, when a ground potential short-circuit abnormality or other-potential short-circuit abnormality occurs in the thermocouple, the potential of the first input unit is affected by the potential of the short-circuit destination, and thus shows a value different from the input reference potential.

  Therefore, by comparing the potential of the first input unit with the input reference potential, it is possible to determine whether there is a short circuit abnormality based on the comparison result. That is, by providing the short circuit abnormality determination unit, it is possible to determine the presence or absence of at least one of the ground potential short circuit abnormality and the other potential short circuit abnormality in the thermocouple based on the comparison result between the potential of the first input unit and the input reference potential.

  Therefore, according to the temperature detection device of the present invention, not only the disconnection abnormality of the thermocouple but also the ground potential short-circuit abnormality of the thermocouple can be detected, and the voltage across the thermocouple becomes negative temperature even in a single power supply configuration. It can detect the temperature in the temperature range that makes the corresponding voltage.

  In the above-described temperature detection device, the signal amplifying unit may be configured to include a plurality of operational amplifiers from the input side connected to the signal input unit to the output side that outputs the temperature detection signal. In addition, the temperature detection apparatus includes an output reference potential setting unit that sets an operation reference potential of an operational amplifier provided on the output side among a plurality of operational amplifiers to an output reference potential higher than a ground potential. Can be taken.

  In the temperature detection device having such a configuration, the output reference potential setting unit is provided on the output side by setting the operation reference potential of the operational amplifier provided on the output side to an output reference potential higher than the ground potential. The voltage range that the operational amplifier can output is determined based on the output reference potential, not the ground potential.

  That is, by providing the output reference potential setting unit, the voltage range that can be output by the signal amplifying unit is not a fixed range set based on the ground potential, but a range set based on the output reference potential. For this reason, even in a single power supply configuration, it is possible to arbitrarily set the voltage range that can be output by the signal amplifier by arbitrarily selecting the output reference potential.

  Therefore, according to the present invention, even in a single power supply configuration, the voltage range that can be output by the signal amplifying unit can be arbitrarily set, so the range of temperature detection signals that can be output is arbitrarily set according to the application. Therefore, a temperature detection device that can be used for a wide range of applications can be realized.

  In the above-described temperature detection device, the ground potential switching unit sets the second input unit and the ground to the energized state in the predetermined disconnection determination period, and the second potential in the predetermined temperature detection period. It is possible to adopt a configuration in which the input unit and the ground are set in a cutoff state.

  In this way, in the disconnection determination period, the ground potential switching unit sets the second input unit and the ground to the energized state, so that it is possible to determine whether there is a disconnection abnormality by the disconnection abnormality determination unit. In the temperature detection period, the second input unit and the ground are set in a cut-off state, thereby suppressing a decrease in temperature detection accuracy due to the second input unit and the ground being energized. it can.

  That is, in this temperature detection device, by clearly distinguishing the temperature detection period and the disconnection determination period, it is possible to reduce the possibility that the temperature detection signal fluctuates due to the influence of the ground potential switching unit during the temperature detection period.

Therefore, according to the present invention, it is possible to determine the disconnection of the thermocouple while reducing the possibility that the temperature detection accuracy is lowered.
In the above-described temperature detection device, a configuration in which the signal amplification unit includes an instrumentation amplifier can be employed.

Since the instrumentation amplifier has a feature that the common-mode rejection ratio is high, it is possible to reduce the influence of noise when detecting a minute voltage output from the thermocouple.
Therefore, according to this invention, the influence of the noise at the time of detecting the output of a thermocouple can be reduced, and the fall of temperature detection accuracy can be suppressed.

  Next, the method of the present invention is an abnormality determination method for a temperature detection device that detects a temperature based on a potential difference between two output ends of a thermocouple, and the temperature detection device is electrically connected to two output ends of a thermocouple. A signal input unit having a first input unit and a second input unit connected to each other, a signal amplifying unit for amplifying a potential difference generated between the first input unit and the second input unit and outputting as a temperature detection signal; The input reference potential setting unit for setting the potential of the first input unit of the input units to an input reference potential higher than the ground potential, and the electrical connection state between the second input unit and the ground potential are energized or cut off. A ground potential switching unit for switching to a state.

  The method according to the present invention includes a ground potential setting step of setting the second input unit and the ground to the energized state by the ground potential switching unit, and a temperature detection in a state where the second input unit and the ground are set to the energized state. The signal is compared with a predetermined disconnection abnormality determination threshold, and the disconnection abnormality determination step for determining the presence or absence of the disconnection abnormality in the thermocouple based on the comparison result is compared with the potential of the first input unit and the input reference potential. And a short circuit abnormality determination step for determining whether or not at least one of a ground potential short circuit abnormality and another potential short circuit abnormality in the thermocouple is based on the comparison result.

  First, the temperature detection apparatus to which the method of the present invention is applied can switch the electrical connection state between the second input unit and the ground to the energized state or the cut-off state by including the ground potential switching unit. For this reason, when determining the presence or absence of a disconnection abnormality in the thermocouple, the ground potential switching unit sets the second input unit and the ground to the energized state and does not determine the presence or absence of a disconnection abnormality (in other words, the temperature In the case of detection), the ground potential switching unit can set the second input unit and the ground to a cut-off state.

  For this reason, a disconnection abnormality determination value for determining whether or not there is a disconnection abnormality is determined in advance, the ground potential setting step is executed, and the disconnection abnormality is performed in a state where the second input unit and the ground are set to the energized state. By executing the determination step and comparing the temperature detection signal with the disconnection abnormality determination value, it is possible to determine whether there is a disconnection abnormality. Thus, in the disconnection abnormality determination step, the second input unit and the ground are set in the energized state, and the temperature detection signal is compared with the disconnection abnormality determination value, so that the disconnection in the thermocouple is performed based on the comparison result. The presence or absence of abnormality can be determined.

  By the way, since the electromotive force of the thermocouple is weak, when the ground potential short circuit abnormality or other potential short circuit abnormality (short circuit to the power supply positive electrode potential) occurs in the thermocouple, the first input unit and the second input unit These potentials are substantially equal to the ground potential or other potentials, and it becomes difficult for the input reference potential setting unit to set the potential of the first input unit to the input reference potential. That is, when a ground potential short-circuit abnormality or another potential short-circuit abnormality occurs in the thermocouple, the potential of the first input unit shows a value different from the input reference potential.

  Therefore, by comparing the potential of the first input unit with the input reference potential, it is possible to determine whether there is a short circuit abnormality based on the comparison result. That is, by performing the short circuit abnormality determination step, it is possible to determine the presence or absence of at least one of the ground potential short circuit abnormality and the other potential short circuit abnormality in the thermocouple based on the comparison result between the potential of the first input unit and the input reference potential.

  Therefore, according to the method of the present invention, not only the disconnection abnormality of the thermocouple but also the ground potential short-circuit abnormality of the thermocouple can be detected.

It is a block diagram of the temperature detection apparatus of embodiment. It is a flowchart showing the processing content of the control processing performed in a control part. It is a timing chart which shows the state of each part of the temperature detection apparatus when the power supply positive electrode potential short circuit abnormality and the ground potential short circuit abnormality of the thermocouple occur. It is a timing chart which shows the state of each part of a temperature detection apparatus when the disconnection abnormality of a thermocouple occurs. It is a block diagram of a 2nd temperature detection apparatus provided with a 2nd signal amplification part. It is a block diagram of a 3rd temperature detection apparatus provided with a 3rd signal amplification part. It is a block diagram of a 4th temperature detection apparatus provided with a mechanical type ground potential switching part.

Embodiments to which the present invention is applied will be described below with reference to the drawings.
In the embodiment described below, a temperature detection device that performs temperature detection using a thermocouple will be described as an example.

[1. First Embodiment]
[1-1. overall structure]
The overall configuration of the temperature detection device of the present embodiment will be described with reference to FIG. FIG. 1 is a configuration diagram of a temperature detection device 1 that performs temperature detection using a thermocouple 3.

  As shown in FIG. 1, the temperature detection device 1 of the present embodiment includes a signal input unit 11, a signal amplification unit 13, an input reference potential setting unit 15, a ground potential switching unit 17, and an output reference potential setting unit 19. And a control unit 21.

  The signal input unit 11 includes a first input unit 31 connected to the positive terminal S + of the thermocouple 3 and a second input unit 33 connected to the negative terminal S− of the thermocouple 3. The first input unit 31 is electrically connected to the AD input terminal ADC (analog-digital conversion input terminal ADC) of the control unit 21.

  The signal amplifying unit 13 includes a so-called instrumentation amplifier (instrumentation amplifier). The input side is electrically connected to the thermocouple 3 via the signal input unit 11, and the output side is the control unit 21. It is electrically connected to the AD input terminal ADC. The signal amplifying unit 13 is connected to the input-side first operational amplifier 35 connected to the first input unit 31, the input-side second operational amplifier 37 connected to the second input unit 33, and the AD input terminal ADC of the control unit 21. Output-side operational amplifier 39, and a plurality of resistance elements R1, R2, R3, R4, R5, R6 connected to each operational amplifier.

  The output potential Vo of the signal amplifying unit 13 is set so that each of the resistance elements R1, R2, R3, R4, R5, and R6 is obtained when the potential of the first input unit 31 is Vi1 and the potential of the second input unit 33 is Vi2. And is expressed by the mathematical formula shown in [Formula 1].

The instrumentation amplifier is an amplifier designed to amplify a weak electric signal, and has a feature that the common mode signal rejection ratio (CMRR) is large.
In other words, the signal amplifying unit 13 amplifies the potential difference generated between the first input unit 31 and the second input unit 33 of the signal input unit 11 (in other words, the voltage across the thermocouple 3 (= Vi1−Vi2)). Then, the amplified signal (Vo) is output to the control unit 21 as the temperature detection signal St.

  The input reference potential setting unit 15 resistance-divides the drive voltage Vref (for example, 5 [V]) to generate two input voltage-dividing resistance elements Ra and Rb for generating the input reference potential Vcm (for example, 2 [V]). An operational amplifier 41 to which the input reference potential Vcm is input to the non-inverting input terminal (+), a resistance element Rc connected between the inverting input terminal (−) of the operational amplifier 41 and the first input unit 31, and an operational amplifier And a resistance element Rd connected between the output terminal 41 and the first input unit 31.

  The operational amplifier 41 outputs a potential (input side set potential Vcs) corresponding to the comparison result between the potential Vi1 of the first input unit 31 and the input reference potential Vcm from the output terminal. As a result, the operational amplifier 41 outputs the input side set potential Vcs from the output terminal so that the potential Vi1 of the first input unit 31 approaches the input reference potential Vcm.

  In this way, the input reference potential setting unit 15 sets the potential Vi1 of the first input unit 31 to a potential (specifically, the input reference potential Vcm) higher than the potential of the ground 49 (ground potential Vg).

  In addition, since the electromotive force of the thermocouple 3 is weak, when the ground potential short circuit abnormality or the power supply positive electrode short circuit abnormality occurs in the thermocouple 3, each potential Vi1 of the first input unit 31 and the second input unit 33 is detected. , Vi2 are substantially equal to the ground potential Vg or the power supply positive electrode potential, and it becomes difficult for the input reference potential setting unit 15 to set the potential Vi1 of the first input unit 31 to the input reference potential Vcm. That is, when a ground potential short circuit abnormality or other potential short circuit abnormality (such as a short circuit to the power supply positive electrode potential) occurs in the thermocouple 3, the potential Vi1 of the first input unit 31 is affected by the potential of the short circuit destination. And a value different from the input reference potential Vcm.

  The ground potential switching unit 17 includes a transistor 43 whose emitter is connected to the ground 49. The transistor 43 has a collector connected to the second input unit 33 via the resistance element Rh, an emitter connected to the base via the resistance element Ri, and a base output of the signal from the control unit 21 via the resistance element Rj. Connected to the terminal (Out-put Port).

  The second input unit 33 is connected to the output terminal of the operational amplifier 41 via the resistance element Re. When the transistor 43 is turned on (energized state), the resistance element Re, A current flows in the order of the resistance element Rh, the transistor 43, and the ground 49. Further, a current also flows from the output terminal of the operational amplifier 41 in the order of the resistance element Rd, the thermocouple 3, the resistance element Rh, the transistor 43, and the ground 49.

  The ground potential switching unit 17 is configured such that the transistor 43 is switched to an ON state (energized state) or an OFF state (cut-off state) in accordance with a drive control signal Sg from the control unit 21.

  When the transistor 43 is turned on, the ground potential switching unit 17 electrically connects the second input unit 33 and the ground 49 (energized state), and electrically connects the second input unit 33 to the ground 49. Connecting.

  Further, the ground potential switching unit 17 electrically insulates the second input unit 33 and the ground 49 (shut off state) by turning off the transistor 43, and the potential Vi2 of the second input unit 33 is arbitrary. It is possible to take a potential of. That is, when the transistor 43 is turned off, the potential Vi2 of the second input unit 33 is not forcibly set to a specific potential by the ground potential switching unit 17, but the potential Vi1 of the first input unit 31 and the thermoelectrics. The potential is determined based on the voltage across the pair 3.

  That is, the ground potential switching unit 17 switches the electrical connection state between the second input unit 33 and the ground 49 to the energized state or the cut-off state according to the drive control signal Sg from the control unit 21. In other words, the ground potential switching unit 17 determines whether or not to set the potential Vi2 of the second input unit 33 in the signal input unit 11 to the ground potential Vg in response to the drive control signal Sg from the control unit 21. Switch.

  The output reference potential setting unit 19 resistance-divides the drive voltage Vref to generate an output reference potential Vco (for example, 2 [V]), and the output reference potential Vco The operational amplifier 45 is input to the inverting input terminal (+), and the resistance element Rn is connected between the inverting input terminal (−) of the operational amplifier 45 and the output terminal. The output terminal of the operational amplifier 45 is connected to the non-inverting input terminal (+) of the output-side operational amplifier 39 of the signal amplifying unit 13 via the resistance element R2 and to the AD input terminal ADC of the control unit 21.

  The operational amplifier 45 outputs the output side set potential Vcr so that the potential of the terminal 47 of the signal amplifying unit 13 (the terminal 47 connected to the output reference potential setting unit 19 of the signal amplifying unit 13) is close to the output reference potential Vco. Output from the terminal.

  In this way, the output reference potential setting unit 19 sets the operation reference potential of the output side operational amplifier 39 in the signal amplification unit 13 to a potential (specifically, the output reference potential Vco) higher than the potential of the ground 49 (ground potential Vg). ).

  The control unit 21 is configured by a so-called microcomputer, and although not shown in detail, has a known configuration, a microprocessor that performs calculation, a RAM that temporarily stores programs and data, a ROM that stores programs and data, An A / D conversion circuit that converts an analog signal into a digital signal is included. The A / D conversion circuit converts an analog signal input from the AD input terminal ADC into a digital signal that can be used by a microprocessor or the like.

  The control unit 21 includes a temperature detection signal St output from the signal amplifying unit 13, an input side set potential Vcs output from the input reference potential setting unit 15, and an output side set potential output from the output reference potential setting unit 19. Vcr is received by the AD input terminal ADC. Further, the control unit 21 includes a signal output terminal (Out-put Port) that outputs a drive control signal Sg to the ground potential switching unit 17.

[1-2. Control processing in control unit 21]
Here, the control process executed in the control unit 21 will be described with reference to the flowchart shown in FIG.

Note that the control process is started when the temperature detection apparatus 1 is activated and continues until the temperature detection apparatus 1 is stopped.
When the control process is started, first, in S110 (S represents a step), an initial setting process including initialization of a RAM operation and the like is performed.

  The initial setting process in S110 includes a process for starting a time counter update process that is separately executed in parallel, a process for setting various parameter values to initial values, and the like. The time counter update process is a process of updating a time counter used for determination processing in S150 and S190 described later according to the elapsed time.

In the next S120, the drive control signal Sg is set to a low level, and the transistor 43 of the ground potential switching unit 17 is controlled to be in an OFF state (cut-off state).
When the transistor 43 is turned off, the second input unit 33 and the ground 49 are electrically insulated (shut off state), and the potential Vi2 of the second input unit 33 is forced by the ground potential switching unit 17. Instead of being set to a specific potential, the potential is determined based on the potential Vi1 of the first input unit 31 and the voltage across the thermocouple 3.

In the next S130, a temperature detection process for detecting the temperature in the temperature sensing part of the thermocouple 3 based on the temperature detection signal St is performed.
Specifically, the voltage across the thermocouple 3 is detected from the temperature detection signal St, and the detected voltage across the thermocouple 3 is determined using a map or a calculation formula showing the correlation between the voltage across the thermocouple 3 and the temperature. Performs processing to calculate temperature.

In the next S140, a short circuit abnormality determination process is performed to determine whether or not there is a ground potential short circuit abnormality or a power supply positive electrode potential short circuit abnormality in the thermocouple 3.
First, regarding the power supply positive electrode potential short-circuit abnormality determination, the input side set potential Vcs is compared with a predetermined positive electrode potential short-circuit abnormality determination value Th1, and the presence or absence of the power supply positive electrode potential short-circuit abnormality in the thermocouple 3 is determined based on the comparison result. Determination is made (see FIG. 3 described later). At this time, if the input side set potential Vcs is smaller than the positive electrode potential short circuit abnormality determination value Th1, it is determined that “positive electrode short circuit abnormality exists”, and the input side set potential Vcs is equal to or greater than the positive electrode potential short circuit abnormality determination value Th1. In this case, it is determined that “the positive electrode potential short-circuit abnormality is not present”.

  Further, regarding the ground potential short circuit abnormality determination, the input side set potential Vcs is compared with a predetermined ground potential short circuit abnormality determination value Th2, and the presence or absence of the ground potential short circuit abnormality in the thermocouple 3 is determined based on the comparison result. (See FIG. 3 described later). At this time, if the input side set potential Vcs is larger than the ground potential short circuit abnormality determination value Th2, it is determined that “the ground potential short circuit abnormality exists”, and the input side set potential Vcs is equal to or smaller than the ground potential short circuit abnormality determination value Th2. In this case, it is determined that “no ground potential short-circuit abnormality”.

  The input side set potential Vcs varies according to the comparison result between the potential Vi1 of the first input unit 31 and the input reference potential Vcm. Therefore, in S140, the potential Vi1 of the first input unit 31 is compared with the input reference potential Vcm, and the presence or absence of the ground potential short circuit abnormality or the power supply positive electrode potential short circuit abnormality in the thermocouple 3 is determined based on the comparison result. Yes.

  In the next S150, it is determined whether or not the temperature detection period has elapsed based on the value of the time counter. If the determination is affirmative, the process proceeds to S160. If the determination is negative, the process proceeds to S130 again. It waits until it affirmation determinates by S150 by repeatedly performing each step of S130-S150.

  When an affirmative determination is made in S150 and the process proceeds to S160, in S160, the drive control signal Sg is set to a high level, and the transistor 43 of the ground potential switching unit 17 is controlled to be in an ON state (energized state). When the transistor 43 is turned on, the second input unit 33 and the ground 49 are electrically connected (energized state), and the second input unit 33 is electrically connected to the ground 49.

  In the next S170, as in S140, a short circuit abnormality determination process is performed to determine whether there is a ground potential short circuit abnormality or a power supply positive electrode potential short circuit abnormality in the thermocouple 3. These processing contents are as described above, and are omitted here.

In the next S180, a disconnection abnormality determination process for determining whether there is a disconnection abnormality in the thermocouple 3 based on the temperature detection signal St is performed.
About the presence or absence of a disconnection abnormality, the temperature detection signal St is compared with a predetermined disconnection abnormality determination value Th3, and the presence or absence of a disconnection abnormality in the thermocouple 3 is determined based on the comparison result (see FIG. 4 described later). At this time, if the temperature detection signal St is larger than the disconnection abnormality determination value Th3, it is determined that “disconnection abnormality exists”, and if the temperature detection signal St is equal to or smaller than the disconnection abnormality determination value Th3, “no disconnection abnormality”. Is determined.

  In the next S190, it is determined whether or not the disconnection abnormality determination period has passed based on the value of the time counter. If an affirmative determination is made, the process proceeds to S170 again, and if a negative determination is made, the same step is repeated. Wait until affirmative determination is made by execution.

  When an affirmative determination is made in S190 and the process proceeds to S200, a process of resetting the time counter is executed in S200. Thereby, the value of the time counter is reset to the initial value (zero), and the time counter counting process by the time counter updating process is continued.

When the process of S200 ends, the process proceeds to S120 again.
As described above, the processing from S120 to S200 is repeatedly executed, so that the temperature detection period and the disconnection abnormality determination period are alternately repeated.

As described above, the temperature detection apparatus 1 repeatedly executes the processing from S120 to S200, thereby alternately performing temperature detection using the thermocouple 3 and disconnection abnormality determination of the thermocouple 3.
[1-3. Timing chart showing the state of each part of temperature detector 1]
Here, FIG. 3 shows a timing chart showing the state of each part of the temperature detection device 1 when the power supply positive potential short circuit abnormality and the ground potential short circuit abnormality of the thermocouple 3 occur.

  In FIG. 3, periods T1, T3, and T5 are temperature detection periods, and periods T2 and T4 are disconnection abnormality determination periods. In FIG. 3, an abnormality occurs in which the thermocouple 3 comes into contact with the power supply positive electrode potential at the time indicated by the arrow “Power supply positive potential short circuit abnormality”, and the thermocouple 3 is generated at the time indicated by the arrow “Ground potential short circuit abnormality”. Represents the state of each part when an abnormality occurs in contact with the ground 49.

  As shown in FIG. 3, when the “power supply positive potential short circuit abnormality” occurs during the period T1, the potential Vi1 of the first input unit 31 rises to the “power supply positive potential”, and the potential of the output terminal of the operational amplifier 41 (input side) The set potential Vcs) decreases and falls below the positive electrode potential short-circuit abnormality determination value Th1. At this time, it is determined that “positive electrode potential short-circuit abnormality exists” by the determination process in S140 described above.

  Further, as shown in FIG. 3, when the “ground potential short-circuit abnormality” occurs during the period T3, the potential Vi1 of the first input unit 31 decreases to the “ground potential Vg”, and the potential of the output terminal of the operational amplifier 41 (input) Side set potential Vcs) rises and exceeds the ground potential short-circuit abnormality determination value Th2. At this time, it is determined that “ground potential short-circuit abnormality exists” by the determination processing in S140 described above.

Next, FIG. 4 shows a timing chart showing the state of each part of the temperature detection device 1 when a disconnection abnormality of the thermocouple occurs.
In FIG. 4, periods T1, T3, and T5 are temperature detection periods, and periods T2 and T4 are disconnection abnormality determination periods. FIG. 4 is a timing chart when a disconnection abnormality of the thermocouple 3 occurs at the time indicated by the arrow of “thermocouple disconnection”.

  When the “disconnection abnormality” does not occur as in the period T1 to the period T2 in FIG. 4, the temperature detection signal St is a value smaller than the disconnection abnormality determination value Th3 even in the disconnection abnormality determination period (period T2). In S180, it is determined that “no disconnection abnormality”.

  On the other hand, when the “disconnection abnormality” occurs in the middle of the period T3 in FIG. 4, the temperature detection signal St indicates a value larger than the disconnection abnormality determination value Th3 in the disconnection abnormality determination period (period T4). It is determined that there is a disconnection abnormality.

[1-4. effect]
As described above, in the temperature detection device 1 of the present embodiment, the input reference potential setting unit 15 sets the potential Vi1 of the first input unit 31 to the input reference potential Vcm, so that the “thermoelectric” in the signal amplification unit 13 is set. The “reference potential of the voltage across the pair 3” (the potential Vi1 of the first input unit 31) is higher than the ground potential Vg (input reference potential Vcm).

  As a result, even when the voltage across the thermocouple 3 becomes a voltage corresponding to the negative temperature, the “two output terminals of the thermocouple 3 (positive terminal S +, negative terminal S−)” input to the signal amplifier 13 In a range where each potential (in other words, each potential Vi1, Vi2 of the first input unit 31 and the second input unit 33) is equal to or higher than the ground potential Vg, the signal amplifying unit 13 Can be amplified. In other words, the provision of the input reference potential setting unit 15 enables temperature detection in a temperature range in which the voltage across the thermocouple 3 is a voltage corresponding to a negative temperature even in a single power supply configuration.

  In addition, by providing the ground potential switching unit 17, the electrical connection state between the second input unit 33 and the ground 49 can be switched between an energized state and a cutoff state. For this reason, when determining the presence or absence of disconnection abnormality in the thermocouple 3, the ground potential switching unit 17 sets the second input unit 33 and the ground 49 to the energized state and does not determine the presence or absence of disconnection abnormality (in other words, In this case, when the temperature is detected, the ground potential switching unit 17 can set the second input unit and the ground 49 to the cutoff state.

  Therefore, a disconnection abnormality determination value Th3 for determining whether or not there is a disconnection abnormality is determined in advance, and the temperature detection is performed in a state where the second input unit 33 and the ground 49 are set to the energized state by the ground potential switching unit 17. By comparing the signal St with the disconnection abnormality determination value Th3, it is possible to determine whether there is a disconnection abnormality. Therefore, the control unit 21 that executes S180 compares the temperature detection signal St with the disconnection abnormality determination value Th3 in a state where the second input unit 33 and the ground 49 are set in the energized state by the ground potential switching unit 17. Thus, it is possible to determine the presence or absence of a disconnection abnormality in the thermocouple 3 based on the comparison result.

  As described above, when the ground potential short-circuit abnormality or the power supply positive electrode potential short-circuit abnormality occurs in the thermocouple 3, the potential Vi1 of the first input unit 31 is affected by the potential of the short-circuit destination, and therefore the input reference potential Vcm. Different values are shown. Therefore, at least the ground potential short-circuit abnormality and the power supply positive electrode potential short-circuit abnormality in the thermocouple 3 are based on the input side set potential Vcs that is a potential corresponding to the comparison result between the potential Vi1 of the first input unit 31 and the input reference potential Vcm. The presence or absence of one can be determined.

  In this embodiment, the control unit 21 that executes S140 or S170 determines whether or not there is a power supply positive electrode potential short-circuit abnormality in the thermocouple 3 based on the comparison result between the input side set potential Vcs and the positive electrode potential short-circuit abnormality determination value Th1. judge. Moreover, the control part 21 which performs S140 or S170 determines the presence or absence of the ground potential short circuit abnormality in the thermocouple 3 based on the comparison result of the input side setting potential Vcs and the ground potential short circuit abnormality determination value Th2.

  Therefore, according to the temperature detection device 1 of the present embodiment, not only the disconnection abnormality of the thermocouple 3 but also the ground potential short-circuit abnormality of the thermocouple 3 can be detected, and both ends of the thermocouple 3 can be detected even in a single power supply configuration. Temperature detection in a temperature range in which the voltage becomes a voltage corresponding to the negative temperature can be performed.

  Next, in the temperature detection device 1, the signal amplification unit 13 includes a plurality of operational amplifiers (input side first operational amplifier 35, input side) from the input side connected to the signal input unit 11 to the output side that outputs the temperature detection signal St. A second operational amplifier 37 and an output side operational amplifier 39) are provided. In addition, the temperature detection device 1 includes an output reference potential setting unit 19 that sets an operation reference potential of an output-side operational amplifier 39 provided on the output side among a plurality of operational amplifiers to an output reference potential Vco that is higher than the ground potential Vg. Prepare. As a result, the voltage range that can be output by the output-side operational amplifier 39 provided on the output side of the signal amplification unit 13 is determined based on the output reference potential Vco instead of the ground potential Vg.

  That is, by providing the output reference potential setting unit 19, the voltage range that can be output by the signal amplification unit 13 is not a fixed range that is set based on the ground potential Vg, but a range that is set based on the output reference potential Vco. . For this reason, even in the single power supply configuration, it is possible to arbitrarily set the voltage range that can be output by the signal amplifying unit 13 by arbitrarily selecting the output reference potential Vco.

  Therefore, according to the temperature detection device 1 of the present embodiment, the voltage range that can be output by the signal amplifying unit 13 can be arbitrarily set, so that the range of the temperature detection signal St that can be output is arbitrarily set according to the application. Temperature detector that can be used for a wide range of purposes.

  In the temperature detection device 1, the ground potential switching unit 17 driven and controlled by the control unit 21 includes the second input unit 33 and the ground 49 in the disconnection determination period (periods T <b> 2 and T <b> 4 in FIGS. 3 and 4). Is set to the energized state, and the second input unit 33 and the ground 49 are set to the cut-off state during the temperature detection period (periods T1, T3, and T5 in FIGS. 3 and 4). The disconnection determination period corresponds to a period in which the processes from S120 to S150 are executed in the control process, and the temperature detection period corresponds to a period in which the processes from S160 to S190 are executed in the control process. Yes.

  Thus, in the disconnection determination period, the ground potential switching unit 17 sets the second input unit 33 and the ground 49 to the energized state, so that the control unit 21 that executes S180 can determine whether there is a disconnection abnormality. It becomes. Further, during the temperature detection period, the second input unit 33 and the ground 49 are set in a cut-off state, so that the temperature can be detected by the control unit 21 that executes S130. At this time, the second input unit 33 and the ground 49 are detected. It is possible to suppress a decrease in temperature detection accuracy due to the energized state.

  That is, in this temperature detection device 1, by clearly distinguishing the temperature detection period and the disconnection determination period, the possibility that the temperature detection signal fluctuates due to the influence of the ground potential switching unit 17 during the temperature detection period can be reduced.

Therefore, according to the temperature detection device 1 of the present embodiment, it is possible to determine the disconnection of the thermocouple 3 while reducing the possibility that the temperature detection accuracy is lowered.
Moreover, in the temperature detection apparatus 1, the signal amplification unit 13 includes an instrumentation amplifier. Since the instrumentation amplifier has a characteristic that the common mode rejection ratio is high, the temperature detection device 1 can reduce the influence of noise when detecting a minute voltage output from the thermocouple 3.

  As for the abnormality detection method in the temperature detection device 1, the control unit 21 executes S160, and the control unit 21 executes S180 in a state where the second input unit 33 and the ground 49 are set to the energized state. And the method of determining the presence or absence of disconnection abnormality in the thermocouple 3 by comparing the temperature detection signal St and the disconnection abnormality determination value Th3 is adopted.

  Thereby, in the state which the 2nd input part 33 and the ground 49 were set to the energized state, the presence or absence of the disconnection abnormality in the thermocouple 3 is determined based on the comparison result of the temperature detection signal St and the disconnection abnormality determination value Th3. be able to.

  Further, regarding the abnormality detection method in the temperature detection device 1, the control unit 21 executes S140 or S170, so that the thermocouple 3 is based on the comparison result between the input side set potential Vcs and the positive electrode potential short circuit abnormality determination value Th1. Whether or not there is a power supply positive electrode potential short circuit abnormality is determined, and whether or not there is a ground potential short circuit abnormality in the thermocouple 3 is determined based on a comparison result between the input side set potential Vcs and the ground potential short circuit abnormality determination value Th2. More specifically, the potential Vi1 of the first input unit 31 is compared with the input reference potential Vcm, and the presence or absence of the ground potential short circuit abnormality or the power supply positive electrode potential short circuit abnormality in the thermocouple 3 is determined based on the comparison result. Yes.

  Thus, by executing S140 or S170 in the control unit 21, the ground potential short-circuit abnormality and the other potential short-circuit abnormality in the thermocouple 3 based on the comparison result between the potential Vi1 of the first input unit 31 and the input reference potential Vcm. The presence or absence of at least one of can be determined.

[1-5. Correspondence with Claims]
Here, the correspondence of the words in the claims and the present embodiment will be described.
The control unit 21 that executes S180 corresponds to an example of a disconnection abnormality determination unit, and the control unit 21 that executes S140 or S170 corresponds to an example of a short circuit abnormality determination unit.

  S160 executed by the control unit 21 corresponds to an example of a ground potential setting step, S180 executed by the control unit 21 corresponds to an example of a disconnection abnormality determination step, and S140 or S170 executed by the control unit 21 corresponds to a short circuit abnormality determination step. It corresponds to an example.

[2. Second Embodiment]
In the above embodiment (hereinafter also referred to as the first embodiment), the configuration including the signal amplifying unit 13 having an instrumentation amplifier as the signal amplifying unit that amplifies the voltage across the thermocouple has been described. A signal amplifying unit having a capacitor and a switch may be used.

Therefore, as a second embodiment, a second temperature detection device 5 including a second signal amplification unit 51 having a capacitor and a switch will be described.
In the following description, the same configurations as those of the first embodiment among the configurations of the second embodiment are the same as those of the first embodiment and the description thereof is omitted, and the configurations of the second embodiment are omitted. A description will be given centering on differences from the first embodiment.

In FIG. 5, the block diagram of the 2nd temperature detection apparatus 5 provided with the 2nd signal amplification part 51 is shown.
The second signal amplifying unit 51 has an input side electrically connected to the thermocouple 3 via the signal input unit 11 and an output side electrically connected to the AD input terminal ADC of the control unit 21.

  The second signal amplification unit 51 includes a first capacitor C1 connected to the first input unit 31 and the second input unit 33, a second capacitor C2 connected to the first capacitor C1 through the second switch S2, The output side operational amplifier 39 connected to AD input terminal ADC of the control part 21, resistance element R7, R8, R9, R10, two 1st switches S1, and two 2nd switches S2 are provided.

  Among these, the first capacitor C1 is connected to the first input unit 31 via the resistance element R7 and the first switch S1, and is connected to the second input unit 33 via the resistance element R8 and the first switch S1. The

  In the second signal amplifying unit 51, the two first switches S1 are turned on (closed state), and the two second switches S2 are turned off (open state). The charge moves to one capacitor C1. Thereafter, when the two first switches S1 are turned off (open), the voltage across the first capacitor C1 becomes a value corresponding to the voltage across the thermocouple 3 (= Vi1-Vi2).

  Thereafter, the two first switches S1 are turned off (open state), and the two second switches S2 are turned on (closed state), so that charge is transferred from the first capacitor C1 to the second capacitor. Moving. Thereafter, when the two second switches S2 are turned off (opened), the voltage across the second capacitor C2 becomes a value corresponding to the voltage across the first capacitor C1.

  Thus, the opening / closing operation of the first switch S1 and the second switch S2 is repeated, so that the voltage across the second capacitor C2 varies according to the change in the voltage across the thermocouple 3. And while the OFF state (open state) of two 2nd switch S2 is continued, the both-ends voltage of the 2nd capacitor | condenser C2 is maintained at a constant value, and the output side operational amplifier 39 becomes the both-ends voltage of the 2nd capacitor | condenser C2. A corresponding temperature detection signal St is output.

  That is, the second signal amplifying unit 51 has a potential difference generated between the first input unit 31 and the second input unit 33 of the signal input unit 11 (in other words, the voltage across the thermocouple 3 (= Vi1−Vi2)). And the amplified signal (Vo) is output to the control unit 21 as the temperature detection signal St.

The opening / closing operation of the first switch S1 and the second switch S2 is controlled by a control device (not shown).
Similar to the temperature detection device 1 of the first embodiment, the second temperature detection device 5 including the second signal amplification unit 51 has not only the disconnection abnormality of the thermocouple 3 but also the ground potential short-circuit abnormality of the thermocouple 3. Even in a single power supply configuration, temperature detection can be performed in a temperature range in which the voltage across the thermocouple 3 is a voltage corresponding to a negative temperature.

  In addition, the second temperature detection device 5 of the second embodiment includes the output reference potential setting unit 19 as in the temperature detection device 1 of the first embodiment, so that the voltage that can be output by the second signal amplification unit 51 is provided. The range is not a fixed range set based on the ground potential Vg, but a range set based on the output reference potential Vco.

  Therefore, according to the second temperature detection device 5 of the second embodiment, the voltage range that can be output by the second signal amplifying unit 51 can be arbitrarily set as in the temperature detection device 1 of the first embodiment. Accordingly, the range of the temperature detection signal St that can be output can be arbitrarily set, and a temperature detection device that can be used for a wide range of applications can be realized.

Here, the correspondence relationship between the words in the claims and the present embodiment will be described. The second signal amplification unit 51 corresponds to an example of the signal amplification unit.
[3. Third Embodiment]
In the first embodiment, the configuration including the signal amplifying unit 13 having the instrumentation amplifier as the signal amplifying unit for amplifying the voltage across the thermocouple has been described, but the signal amplifying unit having one operational amplifier instead of the signal amplifying unit 13 is described. May be used.

Therefore, as a third embodiment, a third temperature detection device 7 including a third signal amplification unit 53 having one operational amplifier will be described.
In the following description, the same configurations as those of the first embodiment among the configurations of the third embodiment are the same as those of the first embodiment, and the description thereof is omitted, and the configurations of the third embodiment are omitted. A description will be given centering on differences from the first embodiment.

In FIG. 6, the block diagram of the 3rd temperature detection apparatus 7 provided with the 3rd signal amplification part 53 is shown.
The third signal amplifying unit 53 includes an output side operational amplifier 39 whose input side is electrically connected to the thermocouple 3 via the signal input unit 11 and whose output side is connected to the AD input terminal ADC of the control unit 21. Resistance elements R11, R12, and R13 are provided.

  The non-inverting input terminal (+) of the output side operational amplifier 39 is connected to the first input unit 31 of the signal input unit 11 via the resistance element R11, and the inverting input terminal (−) of the output side operational amplifier 39 is connected to the resistance element R12. To the second input unit 33 of the signal input unit 11. Further, the resistance element R13 is connected between the inverting input terminal (−) of the output side operational amplifier 39 and the output terminal.

  The third signal amplifying unit 53 having such a configuration is configured such that the potential difference generated between the first input unit 31 and the second input unit 33 of the signal input unit 11 (in other words, the voltage across the thermocouple 3 (= Vi1− Vi2)) is amplified, and the amplified signal (Vo) is output to the control unit 21 as the temperature detection signal St.

  The third temperature detection device 7 including the third signal amplifying unit 53 as described above not only detects the disconnection abnormality of the thermocouple 3 but also the ground potential short-circuit abnormality of the thermocouple 3 in the same manner as the temperature detection device 1 of the first embodiment. Even in a single power supply configuration, temperature detection can be performed in a temperature range in which the voltage across the thermocouple 3 is a voltage corresponding to a negative temperature.

Here, a description will be given of the correspondence relationship between the claims and the present embodiment. The third signal amplifying unit 53 corresponds to an example of the signal amplifying unit.
[4. Fourth Embodiment]
In the first embodiment, the temperature detection device 1 including the ground potential switching unit 17 having a transistor has been described. However, as the ground potential switching unit that switches the electrical connection state between the second input unit 33 and the ground 49, a machine is used. A type switch may be used.

Therefore, as a fourth embodiment, a fourth temperature detection device 9 including a mechanical ground potential switching unit configured by a mechanical switch will be described.
In the following description, the same configurations as those of the first embodiment among the configurations of the fourth embodiment are the same as those of the first embodiment, and the description thereof is omitted, and the configurations of the fourth embodiment are omitted. A description will be given centering on differences from the first embodiment.

In FIG. 7, the block diagram of the 4th temperature detection apparatus 9 provided with the mechanical ground electric potential switching part 55 comprised with the mechanical switch is shown.
The mechanical ground potential switching unit 55 is a mechanical switch connected between the second input unit 33 and the ground 49, and is opened (shut off) or closed according to the drive control signal Sg from the control unit 21. Switch to either state (energized state).

  That is, the mechanical ground potential switching unit 55 sets the electrical connection state between the second input unit 33 and the ground 49 (ground potential Vg) in accordance with the drive control signal Sg from the control unit 21. Switch to state. In other words, whether or not the mechanical ground potential switching unit 55 sets the potential Vi2 of the second input unit 33 in the signal input unit 11 to the ground potential Vg according to the drive control signal Sg from the control unit 21. Switch between.

  The third temperature detection device 7 including such a mechanical ground potential switching unit 55 is not only a disconnection abnormality of the thermocouple 3 but also a ground potential short-circuit abnormality of the thermocouple 3 as in the temperature detection device 1 of the first embodiment. Even in a single power supply configuration, temperature detection in a temperature range in which the voltage across the thermocouple 3 becomes a voltage corresponding to a negative temperature can be performed.

Here, the correspondence relationship between the words in the claims and the present embodiment will be described. The mechanical ground potential switching unit 55 corresponds to an example of the ground potential switching unit.
[5. Other Embodiments]
As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it is possible to implement in various aspects.

  For example, the drive voltage Vref is not limited to 5 [V] and can take any numerical value. Further, the numerical values of the input reference potential Vcm and the output reference potential Vco are not limited to 2 [V], and temperature detection is performed by setting appropriate numerical values according to various conditions such as the temperature detection application and environment. Accuracy can be improved.

  DESCRIPTION OF SYMBOLS 1 ... Temperature detection apparatus, 3 ... Thermocouple, 5 ... 2nd temperature detection apparatus, 7 ... 3rd temperature detection apparatus, 9 ... 4th temperature detection apparatus, 11 ... Signal input part, 13 ... Signal amplification part, 15 ... Input Reference potential setting unit, 17 ... ground potential switching unit, 19 ... output reference potential setting unit, 21 ... control unit, 31 ... first input unit, 33 ... second input unit, 39 ... output side operational amplifier, 49 ... ground, 51 ... 2nd signal amplification part, 53 ... 3rd signal amplification part, 55 ... Mechanical ground potential switching part, Sg ... Drive control signal, St ... Temperature detection signal, Th1 ... Positive electrode potential short circuit abnormality judgment value, Th2 ... Ground potential short circuit Abnormality determination value, Th3: disconnection abnormality determination value, Vcm: input reference potential, Vco: output reference potential, Vcr: output side set potential, Vcs: input side set potential, Vg: ground potential.

Claims (5)

A temperature detection device that detects a temperature based on a potential difference between two output ends of a thermocouple,
A signal input unit having a first input unit and a second input unit electrically connected to two output ends of the thermocouple;
A signal amplifying unit that amplifies a potential difference generated between the first input unit and the second input unit and outputs a temperature detection signal;
An input reference potential setting unit for setting the potential of the first input unit among the signal input units to an input reference potential higher than a ground potential of ground;
A ground potential switching unit that switches an electrical connection state between the second input unit and the ground to an energized state or a disconnected state;
The temperature detection signal is compared with a predetermined disconnection abnormality determination value in a state where the second input unit and the ground are set in an energized state by the ground potential switching unit, and the thermoelectric power is based on the comparison result. A disconnection abnormality determination unit for determining the presence or absence of a disconnection abnormality in the pair;
A short circuit abnormality determination unit that compares the potential of the first input unit with the input reference potential, and determines the presence or absence of at least one of a ground potential short circuit abnormality and another potential short circuit abnormality in the thermocouple based on the comparison result;
A temperature sensing device comprising: The signal amplification unit includes a plurality of operational amplifiers from an input side connected to the signal input unit to an output side that outputs the temperature detection signal,
An output reference potential setting unit that sets an operation reference potential of an operational amplifier provided on an output side of the plurality of operational amplifiers to an output reference potential higher than the ground potential;
The temperature detection device according to claim 1. The ground potential switching unit sets the second input unit and the ground to an energized state during a predetermined disconnection determination period, and the second input unit and the ground during a predetermined temperature detection period. Set the ground and shut-off state,
The temperature detection device according to claim 1 or 2. The signal amplification unit includes an instrumentation amplifier.
The temperature detection device according to any one of claims 1 to 3. An abnormality determination method for a temperature detection device that detects a temperature based on a potential difference between two output ends of a thermocouple,
The temperature detector is
A signal input unit having a first input unit and a second input unit electrically connected to two output ends of the thermocouple;
A signal amplifying unit that amplifies a potential difference generated between the first input unit and the second input unit and outputs a temperature detection signal;
An input reference potential setting unit for setting the potential of the first input unit among the signal input units to an input reference potential higher than a ground potential of ground;
A ground potential switching unit that switches an electrical connection state between the second input unit and the ground to an energized state or a disconnected state;
With
A ground potential setting step of setting the second input unit and the ground to an energized state by the ground potential switching unit;
In a state where the second input unit and the ground are set in an energized state, the temperature detection signal is compared with a predetermined disconnection abnormality determination threshold value, and based on the comparison result, the presence or absence of disconnection abnormality in the thermocouple Disconnection abnormality determination step for determining
A short circuit abnormality determination step of comparing the potential of the first input unit with the input reference potential, and determining the presence or absence of at least one of a ground potential short circuit abnormality and another potential short circuit abnormality in the thermocouple based on the comparison result;
An abnormality determination method for a temperature detecting device having

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