JP2018054351A - Temperature detector, temperature measurement system, and temperature measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a temperature measurement system in which an increase in wiring costs and a system scale are suppressed while maintaining the accuracy of temperature measurement.SOLUTION: A temperature detector 1 according to the present invention comprising a temperature detection function and other functions other than the temperature detection function includes: a first external terminal P1 and a second external terminal P2 for the temperature detection function; a third external terminal P3 for the other functions; a temperature measurement resistive element Rconnected between the first external terminal and the second external terminal; a voltage generation unit 14, having two terminals which respectively are connected between the second external terminal and the third external terminal, for generating a voltage between the two terminals that corresponds to an inputted current; a switch SW1 connected in series to the voltage generation unit between the second external terminal and the third external terminal; and a control unit 11 for turning the switch off when the voltage Vs of the second external terminal is lower than a threshold Vth and turning the switch SW1 on when the voltage of the second external terminal is higher than the threshold.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a temperature detection device using a resistance temperature detector, and a temperature measurement system that measures temperature using the temperature detection device.

  2. Description of the Related Art Conventionally, in an air conditioning control system in a building such as a building, a temperature / humidity measuring device has been used to measure temperature and humidity in a space to be controlled for air conditioning (see, for example, Patent Document 1). As a temperature / humidity measuring apparatus, one that measures temperature using a resistance temperature detector (Pt100) and measures humidity using a polymer capacitive humidity sensing element is known.

  In temperature measurement using a resistance temperature detector, various measurement methods are known in accordance with the connection method between the resistance temperature detector and the measuring instrument. For example, Patent Document 2 discloses a technique using a two-wire temperature measurement circuit and a technique using a three-wire temperature measurement circuit.

JP 2012-154632 A JP 2012-168105 A

  In general, the two-wire temperature measurement method can reduce the wiring cost as compared with the three-wire temperature measurement method, but an error in the measurement temperature based on the wiring resistance occurs.

  On the other hand, with the 3-wire temperature measurement method, it is possible to measure the temperature with high accuracy without being affected by the above-described wiring resistance, but the number of wires is increased compared to the 2-wire temperature measurement method. This leads to an increase in wiring cost and an increase in system scale (product size) due to an increase in the number of terminals.

  Therefore, in the temperature measurement system using the resistance temperature detector, when the two-wire temperature measurement method is adopted, the temperature measurement accuracy is lowered, and when the three-wire temperature measurement method is adopted, There was a problem that the wiring cost increased and the scale of the system increased.

  The present invention has been made in view of the above problems, and an object of the present invention is to realize a temperature measurement system that suppresses an increase in wiring cost and a system scale while maintaining temperature measurement accuracy. .

A temperature detection device having a temperature detection function and a function other than temperature detection according to the present invention includes a first external terminal (P1) and a second external terminal (P2) for the temperature detection function, and other functions. A third external terminal (P3) for function, a resistance temperature detector (R _T ) connected between the first external terminal and the second external terminal, and two terminals, the second external terminal And a third external terminal are connected to each other, a voltage generator (14, R ₁ ) for generating a voltage corresponding to the input current between the two terminals, a second external terminal and a third external terminal The first switch (SW1) connected in series with the voltage generator between the three external terminals and the first switch is turned off when the voltage (Vs) of the second external terminal is lower than the threshold value (Vth). And a control unit (11) for turning on the first switch when the voltage of the second external terminal is higher than the threshold value. It is characterized in.

The temperature detection device further includes a fourth external terminal (P4) for other functions and a voltage output unit (12) for generating and outputting a voltage (V _OUT4 ) related to the other functions, The voltage output unit allows voltage output by the voltage output unit when the voltage of the second external terminal is lower than the threshold value, and stops voltage output by the voltage output unit when the voltage of the second external terminal is higher than the threshold value. Good.

  The temperature detection device may further include a humidity detection element (13), and the voltage output unit may output a voltage generated based on the humidity detection element to the fourth external terminal (P4).

A temperature measurement system according to the present invention includes the temperature detection device and a measurement device (2) electrically connected to the temperature detection device, and the measurement device has a first external terminal in a wiring resistance measurement mode, A first estimated value (R _{T_1} ) of the resistance value of the resistance temperature detector is calculated by three-wire temperature measurement using the second external terminal and the third external terminal, and the first external terminal and the second external terminal The second estimated value (R _{T_2} ) of the resistance value of the resistance temperature detector is calculated by two-wire temperature measurement using a temperature sensor, and based on the difference between the first estimated value and the second estimated value, The wiring resistance (2r) of the wiring (L1, L2) connecting between the measuring instruments is calculated, and in the temperature measurement mode, the third estimated value (R) of the resistance value of the resistance thermometer element is measured by two-wire temperature measurement. _{T_3)} is calculated, the third estimated value calculated, calculated in wiring resistance measurement mode And calculates the true value of the resistance values of the temperature measuring resistance element is corrected by the wiring resistance (2r).

  In the temperature measurement system, the measuring instrument calculates a difference between the first estimated value and the second estimated value a plurality of times in the wiring resistance measurement mode, and calculates a wiring resistance based on an average value of the plurality of the differences. Also good.

In the temperature measurement system, the measuring instrument includes a fifth external terminal (P5) electrically connected to the first external terminal, a sixth external terminal (P6) electrically connected to the second external terminal, A seventh external terminal (P7) electrically connected to the third external terminal and connected to the ground potential of the measuring instrument, and a second connected between the sixth external terminal and the ground potential of the measuring instrument. The data processing control unit includes a switch (SW2) and a data processing control unit (21). In the wiring resistance measurement mode, the data processing control unit has the fifth external terminal and the sixth external terminal in a state where the second switch of the measuring instrument is turned off. _Are supplied with currents (I _OUT1 , I _OUT2 ), respectively, and a first estimated value (R _{T_1} ) is calculated based on the voltage and current of the fifth external terminal and the voltage and current of the sixth external terminal at that time, Second switch (SW2) turned on In 5 supplies current to the external terminal, calculates a second estimated value based on the voltage and current of the fifth external terminal at that time (R _{T_2),} in the temperature measuring mode, it turns on the second switch of the instrument In this state, a current is supplied to the fifth external terminal, a third estimated value (R _{T —} 3) is calculated based on the voltage and current of the fifth external terminal at that time, and the third estimated value and the wiring resistance value are calculated. This difference may be the true value of the resistance value of the resistance temperature detector.

The temperature measurement system further includes an eighth external terminal (P8) electrically connected to the fourth external terminal, and the data processing control unit includes the seventh external terminal and the eighth external terminal in the temperature measurement mode. Humidity may be calculated based on the voltage between (V _OUT4 ).

  The temperature measurement method according to the present invention includes a temperature measurement system having the temperature detection device and a measuring instrument having fifth to eighth external terminals, wherein the first to fourth external terminals are connected to the fifth to eighth external terminals. A temperature measurement method for measuring temperature in a state where each of the terminals is connected to each other by a signal line, the voltage and current of the fifth external terminal when the measuring device outputs current from the fifth external terminal and the sixth external terminal, The first step (S14) for calculating the first estimated value of the resistance value of the resistance temperature detector from the voltage and current of the sixth external terminal, and the measuring instrument connected the sixth external terminal to the ground potential of the measuring instrument A second step (S18) for calculating a second estimated value of the resistance value of the resistance temperature detector based on the voltage and current of the fifth external terminal when current is output from the fifth external terminal in a state; Is calculated in the first step Based on the difference between the first estimated value and the second estimated value calculated in the second step, a third step (S19) for calculating the wiring resistance (2r) of the signal line connecting the temperature detecting device and the measuring instrument. ) And the temperature measurement based on the voltage and current of the fifth external terminal when the current is output from the fifth external terminal with the sixth external terminal connected to the ground potential (GND2) of the measurement instrument. Obtained by subtracting the wiring resistance calculated in the third step from the third estimated value calculated in the fourth step (S24) for calculating the third estimated value of the resistance value of the resistance element. And a fifth step (S25) for calculating the temperature from the true value of the resistance value of the obtained resistance thermometer element.

  In the above description, as an example, reference numerals on the drawings corresponding to the constituent elements of the invention are shown in parentheses.

  As described above, according to the present invention, it is possible to realize a temperature measurement system that increases the wiring cost and suppresses the scale of the system while maintaining the temperature measurement accuracy.

It is a figure which shows the structure of the temperature measurement system provided with the temperature detection apparatus which concerns on one embodiment of this invention. It is a flowchart which shows the flow of the process which concerns on the measurement of the temperature and humidity by a temperature measurement system. It is a flowchart which shows the flow of the process in wiring resistance measurement mode. It is a figure which shows the connection relation of the temperature detection apparatus and measuring instrument in wiring resistance measurement mode. It is a figure which shows the structure of a 3-wire type temperature measurement circuit. It is another figure which shows the connection relation of the temperature detection apparatus and measuring instrument in wiring resistance measurement mode. It is a figure which shows the structure of a 2-wire type temperature measurement circuit. It is a flowchart which shows the flow of the process in normal measurement mode. It is a figure which shows the connection relation of the temperature detection apparatus and measuring instrument in normal measurement mode.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same reference numerals are given to components common to the respective embodiments, and repeated description is omitted.

FIG. 1 is a diagram illustrating a configuration of a temperature measurement system including a temperature detection device according to an embodiment of the present invention.
A temperature measurement system 100 shown in FIG. 1 measures the temperature of the space based on a temperature detection device 1 that detects the temperature of the installed space and an electrical signal corresponding to the temperature detected by the temperature detection device 1. The measuring instrument 2 is provided.

  In the present embodiment, a case where temperature measurement system 100 is a part of an air conditioning control system will be described as an example. Specifically, the temperature detection device 1 is a temperature / humidity detection device that is installed in a space subject to air conditioning control and detects the temperature and humidity of the space, and the measuring instrument 2 is based on a signal from the temperature detection device 1. The controller has a function of calculating temperature and humidity and a function of controlling the air conditioner 3 such as a fan coil unit based on the measured temperature and humidity.

  As shown in FIG. 1, the temperature detection device 1 and the measuring instrument 2 are electrically connected by a plurality of wires L1 to L4, and voltage and current can be input and output between the temperature detection device 1 and the measuring instrument 2. It has become.

  Specifically, the temperature detection device 1 has, as external terminals, terminals P1 and P2 for the temperature detection function and other functions other than the temperature detection function, that is, terminals P3 and P4 for the humidity detection function. ing. Further, the measuring instrument 2 has, as external terminals, terminals P5 and P6 for the temperature measuring function and other functions other than the temperature measuring function, that is, terminals P7 and P8 for the humidity measuring function.

  As shown in FIG. 1, the terminal P1 and the terminal P5 are connected by the wiring L1, the terminal P2 and the terminal P6 are connected by the wiring L2, the terminal P3 and the terminal P7 are connected by the wiring L3, and the terminal P4 is connected. The terminal P8 is connected by a wiring L4.

  Here, the wiring resistances of the wirings L1 to L4 are expressed as “r1 to r4”, respectively. In this embodiment, as an example, “r1 = r2 = r3 = r4 = r” will be described. However, at least the wiring resistance r1 and the wiring resistance r2 may have the same resistance value, and the wiring resistances r1 and r2 and the wiring resistance The resistors r3 and r4 do not necessarily have the same resistance value.

Specifically, the temperature detection device 1 includes a resistance temperature detector R _T , a switch SW 1, a control unit 11, a voltage output unit 12, a humidity detection element 13, and a voltage generation unit 14.

The resistance temperature detector _RT is a resistance composed of a resistance temperature detector (for example, Pt100), and has one end connected to the terminal P1 and the other end connected to the terminal P2.

The voltage generation unit 14 is a functional unit that has two terminals connected between the terminal P2 and the terminal P3, and generates a voltage corresponding to the input current between the two terminals. In the present embodiment, the voltage generation unit 14 is described as being the resistor R ₁ , but the present invention is not limited to this.

  The switch SW1 is connected in series with the voltage generator 14 between the terminal P2 and the terminal P3, and opening / closing (ON / OFF) is controlled by the controller 11 described later. Here, the terminal P3 to which one end of the switch SW1 is connected is connected to the internal ground potential GND1 of the temperature detection device 1 inside the temperature detection device 1.

  The humidity detection element 13 is an element whose capacitance changes according to humidity, and is, for example, a polymer capacitive humidity detection element.

  The voltage output unit 12 is a functional unit that generates a voltage (humidity detection signal) corresponding to the capacitance at both ends of the humidity detection element 13 (change in capacitance of the polymer capacitive humidity detection element) and outputs the voltage to the terminal P4. is there.

The control unit 11 is a functional unit that controls opening and closing of the switch SW1 and voltage output by the voltage output unit 12 based on the voltage Vs of the terminal P2. Specifically, when the voltage Vs at the terminal P2 is lower than the threshold value Vth, the control unit 11 turns off the switch SW1, permits the output of the humidity detection signal by the voltage output unit 12, and outputs the temperature detection signal from the terminal P4. As a result, a voltage V _OUT4 is output. On the other hand, when the voltage Vs at the terminal P2 is higher than the threshold value Vth, the control unit 11 turns on the switch SW1 and stops the output of the humidity detection signal by the voltage output unit 12. At this time, the terminal P4 has, for example, high impedance.

  The measuring instrument 2 has, as operation modes, a “wiring resistance measurement mode” for measuring the resistance (wiring resistance) of the wirings L1 and L2 that electrically connect the temperature sensing device 1 and the measuring instrument 2, and the temperature sensing device 1 And a “normal measurement mode” for measuring temperature and humidity based on the above signal.

In the wiring resistance measurement mode, the measuring instrument 2 is based on a three-wire temperature measurement method using the terminals P1 to P3 of the temperature detection device 1, and the first estimated value R _{T_1} of the resistance value of the resistance temperature detector _RT. to calculate the, on the basis of the temperature measurement method of the two-wire with terminal P1 and the terminal P3, calculates a second estimated value R _{T_2} of the resistance values of the temperature measurement resistive element R _T, the first estimate R _{T_1} And the wiring resistances r1 and r2 of the wirings L1 and L2 connecting the temperature detection device 1 and the measuring instrument 2 are calculated based on the difference (R _{T_2} −R _{T_1} ) between the second estimated value R _{T_2} and the second estimated value R _{T_2} .

On the other hand, in the temperature measurement mode, the measuring instrument 2 calculates the third estimated value _{RT_3} of the resistance value of the resistance temperature detector _RT based on the two-wire temperature measuring method, and calculates the calculated third estimated value _{RT_3.} Is corrected by the wiring resistances r1 and r2 calculated in the wiring resistance measurement mode, thereby calculating the resistance value of the resistance temperature detector _RT .

Specifically, the measuring instrument 2 includes a switch SW2 and a data processing control unit 21.
The switch SW2 is connected between the terminal P6 and the internal ground potential GND2 of the measuring instrument 2, and the opening / closing (on / off) of the switch SW2 is controlled by the data processing control unit 21 described later.

  The terminal P7 is connected to the internal ground potential GND2 of the measuring instrument 2 inside the measuring instrument 2.

  The data processing control unit 21 calculates the temperature and humidity of the space to be controlled by the air conditioner 3 based on the signal output from the temperature detection device 1, and controls the air conditioner 3 based on the calculated temperature and humidity. It is a functional part. The data processing control unit 21 includes, for example, a program processing device such as a microcontroller, various interface circuits for realizing communication with the air conditioner 3, and the like.

Specifically, the data processing control unit 21 calculates the wiring resistance in the wiring resistance measurement mode, and calculates the resistance value of the resistance temperature detector _RT measured based on the two-wire temperature measurement method in the temperature measurement mode. The temperature of the control target space is measured by correcting the estimated value by the wiring resistance, and the humidity of the control target space is measured based on the voltage V _OUT4 output from the temperature detection device 1.

  Hereinafter, a method for measuring temperature and humidity by the temperature measurement system 100 will be described in detail with reference to the drawings.

FIG. 2 is a flowchart showing a flow of processing relating to temperature and humidity measurement by the temperature measurement system.
As shown in FIG. 2, the temperature measurement system 100 first operates in the wiring measurement mode before starting temperature measurement (S1). In the wiring measurement mode, a circuit for temperature measurement is temporarily switched to a three-wire temperature measurement circuit, and the wiring resistances of the wirings L1 and L2 are calculated.

Next, the temperature measurement system 100 shifts to the normal measurement mode and measures temperature and humidity (S2). In the normal measurement mode, the temperature measurement circuit is switched to a two-wire temperature measurement circuit, an estimated value of the resistance value of the resistance temperature detector _RT is calculated, and the estimated value is calculated in the wiring measurement mode. By correcting with resistance, the temperature is measured and the humidity is measured from the voltage based on the polymer capacitive humidity sensing element.

  Here, the transition to the wiring measurement resistance mode, that is, the execution of the wiring resistance calculation process (step S1) may be performed at least once before the temperature measurement is performed in the normal measurement mode. For example, when the temperature measurement system 100 is activated, the wiring measurement resistance mode may be shifted only once, or the wiring measurement resistance mode may be periodically shifted using a timer or the like. Alternatively, the temperature may be shifted to the wiring resistance measurement mode each time before the temperature measurement is performed in the normal measurement mode.

Next, the flow of processing in the wiring resistance measurement mode will be described in detail.
FIG. 3 is a flowchart showing the flow of processing in the wiring resistance measurement mode.
In the initial state after activation of the temperature measurement system 100, for example, as shown in FIG. 1, on the data processing device 2 side, the switch SW2 is turned on and the terminal P6 is connected to the ground potential GND2. On the other hand, on the temperature detection device 1 side, since the potential Vs of the terminal P2 is lower than the threshold value Vth, the switch SW1 is turned off, and the voltage output unit 12 can output a voltage to the terminal P4. Yes.

The temperature measurement system 100 first shifts to the wiring resistance measurement mode after starting (step S1).
In the wiring resistance measurement mode, first, as shown in FIG. 4, the data processing controller 21 on the measuring instrument 2 turns off the switch SW2, outputs the current I _OUT1 from the terminal P5, and outputs the current I _OUT2 from the terminal P6. Output (S11). As a result, the voltage Vs at the terminal P2 on the temperature detection device 1 side rises and exceeds the threshold value Vth (S12).

  When detecting that the voltage Vs exceeds the threshold value Vth, the control unit 11 on the temperature detection device 1 side turns on the switch SW1 and stops the voltage output from the voltage output unit 12 to the terminal P4 (S13). Thereby, a three-wire temperature measurement circuit is realized between the temperature detection device 1 and the measuring instrument 2.

At this time, the current I _OUT1 and the current I _OUT2 flow into the internal ground potential GND2 of the measuring instrument 2 via the resistor R ₁ , the switch SW1, the terminal P3, and the terminal P7, so that the voltage Vs of the terminal P2 becomes the threshold value Vth. Will remain above.

At this time, one terminal of the switch SW1 is connected to the internal ground potential GND1 on the temperature detection device 1 side and the internal ground potential GND2 on the measuring instrument 2 side via the terminal P3 and the wiring L3. The impedance viewed from the measuring instrument 2 as the sources of the currents I _OUT1 and I _OUT2 is lower at the internal ground potential GND2 than at the internal ground potential GND1. Therefore, the currents I _OUT1 and I _OUT2 mainly flow from the switch SW1 to the internal ground potential GND2 via the terminal P3, and hardly flow into the internal ground GND1.

  Next, the data processing control unit 21 on the measuring instrument 2 side performs three-wire temperature measurement (S14). Hereinafter, the three-wire temperature measurement method will be described in detail.

FIG. 5 is a diagram showing a configuration of a three-wire temperature measurement circuit.
The temperature measurement circuit 101 shown in the figure shows only the portion related to the three-wire temperature measurement in the temperature measurement system 100 shown in FIG.

  As shown in FIG. 5, in the three-wire temperature measurement, three wires L1 to L3 are used, and ideally, wires L1 to L3 having the same length and resistance are used. Here, for convenience of explanation, it is assumed that the wiring resistance r1 = r2 = r3 = r.

In the three-wire temperature measurement, the difference between the voltage at the terminal P5 and the voltage at the terminal P6 when the same current flows from the terminal P5 and the terminal P6 is measured without being affected by the wiring resistance r. It becomes possible to measure the resistance value of the temperature resistance element _RT . Details will be described below.

First, when the current I _OUT1 is supplied from the terminal P5 and the current I _OUT2 is supplied from the terminal P6, the voltage V _{OUT1 at the} terminal P5 and the voltage V _{OUT2 at the} terminal P6 are expressed by equations (1) and (2), respectively. Can do. Here, _RT represents the true resistance value of the resistance temperature detector _RT . Also, I _OUT1 = I _OUT2 = I and r1 = r2 = r.

Next, when the difference between the voltage V _OUT1 and the voltage V _OUT2 is taken, Expression (3) is obtained.

By changing Equation (3), the resistance temperature detector _RT can be expressed by Equation (4).

As understood from the equation (4), the three-wire temperature measurement circuit 101 can measure the resistance value of the resistance temperature detector _RT without being affected by the wiring resistance r. In general, the resistance of a resistance temperature detector changes depending on the ambient temperature, and since the relationship between the resistance value and the temperature is known in advance, the temperature can be measured by measuring the resistance value.

Therefore, in step S14 of FIG. 3, the voltage V _OUT1 of the terminal P5 when the data processing control unit 21 outputs the currents I _OUT1 and I _OUT2 (I _OUT1 = I _OUT2 = I) from the terminals P5 and P6, respectively. Then, the voltage V _{OUT2 of the} terminal P6 and the current I are measured, and the resistance value of the resistance temperature detector _RT is calculated by solving the above equation (4) based on the measured values.

Hereinafter, the resistance value of the resistance temperature detector _RT calculated in step S14 is referred to as a first estimated value _{RT_1} of the resistance value of the resistance temperature detector _RT . Data of the calculated first estimated value R _{T —} 1 is stored in, for example, a storage unit (not shown) in the data processing control unit 21.

Next, as shown in FIG. 6, the data processing control unit 21 stops the output of the current I _OUT2 to the terminal P6 and turns on the switch SW2 (S15). At this time, the data processing control unit 21 does not stop the output of the current I _OUT1 to the terminal P5. As a result, the voltage Vs at the terminal P2 on the temperature detection device 1 side falls below the threshold value Vth (S16).

  Upon receiving that the voltage Vs has decreased below the threshold value Vth, the control unit 11 turns off the switch SW1 and enables the voltage output unit 12 to output a voltage to the terminal P4 as shown in FIG. 6 (S17). ).

  Next, the data processing control unit 21 performs two-wire temperature measurement (S18). Hereinafter, the two-wire temperature measurement method will be described in detail.

  FIG. 7 is a diagram illustrating a configuration of a two-wire temperature measurement circuit. The temperature measurement circuit 102 shown in the figure shows only the circuit related to the two-wire temperature measurement in the temperature measurement system 100 shown in FIG.

As shown in FIG. 7, in the two-wire temperature measurement, the voltage at the terminal P5 when the current I _OUT1 is supplied from the terminal P5 to the ground potential GND2 on the measuring instrument 2 side via the resistance temperature detector _RT. By measuring V _OUT1 and current I _OUT1 , the resistance value of the resistance temperature detector _RT can be estimated.

Specifically, in the temperature measurement circuit 102, the voltage V _{OUT1 at the} terminal P5 when the current I _OUT1 is supplied from the terminal P5 can be expressed by the following equation (5). Here, I _OUT1 = I.

  By transforming equation (5), equation (6) is obtained.

As can be understood from formula (6), according to the temperature measuring method of two-wire, as an estimate of the resistance values of the temperature measurement resistive element R _T, not only the resistance thermometer element R _T, the terminal P5 and the terminal A resistance value “2r + R _T ” including the wiring resistance 2r to P6 is calculated.

In step S18 of FIG. 3, the data processing control unit 21 measures the voltage V _OUT1 and the current I _OUT1 at the terminal P5 when the current I _OUT1 (= I) flows from the terminal P5, and based on these measured values. Then, the resistance value of the resistance temperature detector _RT is estimated by solving the above equation (6).

Hereinafter, the estimated value of the resistance value of the resistance temperature detector _RT calculated in step S18 is set as a second estimated value _{RT_2} of the resistance value of the resistance temperature detector _RT . The data of the second estimated value _{RT_2} is stored in, for example, a storage unit (not shown) in the data processing control unit 21.

Next, the data processing control unit 21 calculates the wiring resistance r (S19). Specifically, the data processing control unit 21, the resistance value of the temperature measurement resistive element R _T calculated by the second estimated value R _{T_2} and step S15 in the resistance values of the temperature measurement resistive element R _T calculated in Step S18 1 estimated value R _{T_1} is read from the storage unit, a difference between the second estimated value R _{T_2} and the first estimated value R _{T_1} is calculated according to the following equation (7), and the value is stored in the storage unit as the wiring resistance 2r. To do.

  When the process of step S19 is completed, the temperature measurement system 100 shifts from the wiring resistance measurement mode to the normal measurement mode.

Next, the flow of processing in the normal measurement mode will be described in detail.
FIG. 8 is a diagram showing a flow of processing in the wiring resistance measurement mode.
First, as shown in FIG. 8, the data processing control unit 21 on the measuring instrument 2 turns on the switch SW2 (S21). As a result, the voltage Vs at the terminal P2 on the temperature detection device 1 side becomes lower than the threshold value Vth (S22).

  Next, when the control unit 11 on the temperature detection device 1 side detects that the voltage Vs has dropped below the threshold value Vth, the switch SW1 is turned off and voltage output to the terminal P4 by the voltage output unit 12 is enabled. (S23).

Next, the data processing control unit 21 performs two-wire temperature measurement (S24). Specifically, as shown in FIG. 9, when a current I _OUT1 (= I) is supplied from the terminal P5 in a state where a two-wire temperature measurement circuit is configured, the voltage V _OUT1 and the current I at the terminal P5. The resistance value of the resistance temperature detector _RT is estimated by measuring _OUT1 and solving the above equation (6) based on the measured values. Hereinafter, an estimate of the resistance values of the temperature measurement resistive element R _T calculated in step S24, the third estimate R _{T_3} of the resistance values of the temperature measurement resistive element R _T. The data of the second estimated value R _{T — 3} is stored in, for example, a storage unit (not shown) in the data processing control unit 21.

Next, the data processing control unit 21, by calculating the true value R _T of the resistance values of the temperature measurement resistive element R _T, determining the temperature (S25). Specifically, reads the third estimated value R _{T_3} the wiring resistance 2r of the resistance values of the temperature measurement resistive element R _T stored in the storage unit, according to the above formula (8), the third estimate R _{T_3} the wiring resistance 2r is subtracted from the value and the true value R _T of the resistance values of the temperature measurement resistive element R _T. The data processing control unit 21 obtains the temperature based on this true value _RT .

Next, the data processing control unit 21 obtains humidity based on the voltage supplied to the terminal P8 (S26). Specifically, the humidity is calculated based on the voltage V _OUT4 of the terminal P8 with reference to the potential (GND2) of the terminal P7.
With the above processing, it is possible to simultaneously measure temperature and humidity in the normal measurement mode.

As described above, according to the temperature detection device 1 according to the present embodiment, the resistance temperature element _RT is connected between the terminal P1 and the terminal P2 for the temperature detection function, and other functions (other than temperature measurement) For example, the switch SW2 and the voltage generator 14 (resistor R ₁ ) are connected in series between the terminal P3 and the terminal P2 for measuring humidity, and the control unit 11 switches based on the magnitude of the voltage Vs of the terminal P2. By controlling the opening and closing of SW2, the usage of terminal P3 and wiring L3 connected thereto can be switched. Specifically, by supplying current to the terminals P1 and P2 and turning on the switch SW2, the terminal P3 can be used for three-wire temperature measurement, while the current supply to the terminal P2 is stopped. By turning off the switch SW2, the terminal P3 can be used for two-wire temperature measurement.

By constructing the above-described temperature measurement system 100 using the temperature detection device 1, the wiring resistance is measured by a three-wire system in the wiring resistance measurement mode, and the wiring measured in the wiring resistance measurement mode in the normal measurement mode. By correcting the estimated value of the resistance value of the resistance temperature detector _RT measured by the two-wire method using the terminals P1 and P2 using the resistor, the temperature can be measured with the same measurement accuracy as the three-wire temperature measurement method. Can be measured.

  Further, by using the temperature detection device 1, the terminals P3 and P4 used for functions other than the temperature measurement and the wirings L3 and L4 connected to them are temporarily set to the temperature (wiring) in the wiring resistance measurement mode. In order to obtain the same measurement accuracy as the three-wire temperature measurement, it is newly added to the temperature detection device 1 in order to obtain the measurement accuracy equivalent to the three-wire temperature measurement. There is no need to provide terminals, and there is no need to increase the wiring between the measuring instruments.

  Therefore, according to the temperature detection device 1 according to the present embodiment, it is possible to realize a temperature measurement system that suppresses an increase in wiring cost and product size while maintaining temperature measurement accuracy.

The temperature detection device 1 further includes a voltage output unit 12 that generates a voltage related to functions other than temperature measurement (for example, a voltage related to humidity) and outputs the voltage to the terminal P4, and the control unit 11 controls the voltage at the terminal P2. Since whether or not voltage output by the voltage output unit 12 is controlled based on the magnitude of Vs, when the temperature measurement system 100 described above is constructed, functions other than temperature measurement from the terminal P4 in the wiring resistance measurement mode. The voltage can be output from the terminal P4 in the normal measurement mode.
According to this, the temperature measurement system 100 can prevent malfunction due to receiving an unnecessary signal from the terminal P4 in the wiring resistance measurement mode, and in the normal measurement mode, other than the temperature measurement function and the temperature measurement. It is possible to achieve both functions. For example, in the normal measurement mode, temperature measurement and humidity measurement can be performed simultaneously.

  Although the invention made by the present inventors has been specifically described based on the embodiments, it is needless to say that the present invention is not limited thereto and can be variously modified without departing from the gist thereof. Yes.

For example, in the above embodiment, the temperature detection device 1 is provided with a humidity detection function as a function other than the temperature detection and includes the terminals P3 and P4 for the humidity detection function. Absent. For example, instead of the humidity detection function, a function of detecting the emission amount of carbon dioxide (CO ₂ ) may be used. Specifically, the temperature detection device 1 includes a carbon dioxide emission detection unit that detects carbon dioxide emission instead of the humidity detection element 13, and the voltage output unit 12 detects from the carbon dioxide emission detection unit. A voltage corresponding to the signal may be output from the terminal P4. According to this, the temperature detection system 100 can calculate the wiring resistance in the wiring resistance measurement mode, and can simultaneously measure the temperature and the carbon dioxide emission amount in the normal measurement mode.

In the above embodiment, the case where the true value _RT of the resistance value of the resistance temperature detector is calculated in the normal measurement mode using the wiring resistance measured only once in the wiring measurement mode is illustrated. Not limited. For example, the wiring resistance may be measured a plurality of times in the wiring resistance measurement mode, and the average value of the measured values may be used as the wiring resistance 2r to calculate the true value _RT of the resistance value of the resistance temperature detector.

  In the above embodiment, the case where the switch SW1 is off and the switch SW2 is on is illustrated as an initial state of the temperature measurement system 100. However, the present invention is not limited to this. For example, as an initial state, the switch SW1 may be on and the switch SW2 may be off.

In the above embodiment, the temperature sensing device 1, is connected with a voltage generator 14 (resistance R ₁₎ to the terminal P2 side, a case has been exemplified that connect the switch SW2 to the terminal P3 side terminal P2 and the terminal if blocking the formation of the current path via the resistor R ₁ between P3 is long and is configured to be switched, there is no particular limitation on the circuit configuration. For example, the connection between the voltage generator 14 (resistor R ₁ ) and the switch SW2 may be switched.

  In the above embodiment, for convenience of explanation, the case where the magnitude of the current output from the measuring instrument 2 side is the same in the two-wire type and the three-wire type (IOUT1 = I) is exemplified. However, the current may be output differently between the 2-wire system and the 3-wire system.

DESCRIPTION OF SYMBOLS 100 ... Temperature measurement system, 101 ... Three-wire type temperature measurement circuit, 102 ... Two-wire type temperature measurement circuit, 1 ... Temperature detection apparatus, 2 ... Measuring instrument, 3 ... Control object apparatus, 11 ... Control part, 12 ... voltage output unit, 13 ... humidity sensing element, 21 ... data processing control unit, SW1, SW2 ... switch, P1 to P8 ... terminal, R ₁ ... resistor, R _T ... resistance temperature device, r1 to r4, r ... wiring resistance , V _OUT1 , V _OUT2 , V _OUT4 , Vs... Voltage, I _OUT1 , I _OUT2 , I... Current, GND 1, internal ground potential of the temperature detector 1, GND 2, internal ground potential of the measuring instrument 2.

Claims (8)

A temperature detection device having a temperature detection function and a function other than temperature detection,
A first external terminal and a second external terminal for the temperature detection function;
A third external terminal for the other function;
A resistance temperature element connected between the first external terminal and the second external terminal;
A voltage generator having two terminals, the two terminals being connected between the second external terminal and the third external terminal, respectively, and generating a voltage according to the input current between the two terminals. And
A first switch connected in series with the voltage generator between the second external terminal and the third external terminal;
A temperature detection unit including: a control unit that turns off the first switch when the voltage of the second external terminal is lower than a threshold; and turns on the first switch when the voltage of the second external terminal is higher than the threshold. apparatus. The temperature detection device according to claim 1,
A fourth external terminal for the other function;
A voltage output unit that generates and outputs a voltage related to the other function;
The control unit enables voltage output by the voltage output unit when the voltage of the second external terminal is lower than a threshold, and the voltage by the voltage output unit when the voltage of the second external terminal is higher than the threshold. A temperature detector characterized by stopping output. The temperature detection device according to claim 2,
A humidity sensing element;
The temperature detection device, wherein the voltage output unit outputs a voltage generated based on the humidity detection element to the fourth external terminal. The temperature detection device according to claim 2 or 3,
A measuring instrument electrically connected to the temperature sensing device;
The measuring instrument is
In the wiring resistance measurement mode, a first estimated value of the resistance value of the resistance temperature detector is calculated by three-wire temperature measurement using the first external terminal, the second external terminal, and the third external terminal. In addition, a second estimated value of the resistance value of the resistance temperature detector element is calculated by two-wire temperature measurement using the first external terminal and the second external terminal, and the first estimated value and the second estimated value are calculated. Based on the difference between the values, calculate the wiring resistance of the wiring connecting the temperature detection device and the measuring instrument,
In the temperature measurement mode, a third estimated value of the resistance value of the resistance temperature sensor is calculated by two-wire temperature measurement, and the calculated third estimated value is calculated by the wiring resistance calculated in the wiring resistance measurement mode. Correcting and calculating the true value of the resistance value of the said resistance temperature sensor element. The temperature measurement system characterized by the above-mentioned. The temperature measurement system according to claim 4,
In the wiring resistance measurement mode, the measuring device calculates a difference between the first estimated value and the second estimated value a plurality of times, and calculates the wiring resistance based on an average value of the plurality of the differences. A characteristic temperature measurement system. The temperature measurement system according to claim 5,
The measuring instrument is
A fifth external terminal electrically connected to the first external terminal;
A sixth external terminal electrically connected to the second external terminal;
A seventh external terminal electrically connected to the third external terminal and connected to a ground potential of the measuring instrument;
A second switch connected between the sixth external terminal and the ground potential of the measuring instrument;
Including a data processing control unit,
The data processing control unit
In the wiring resistance measurement mode, current is supplied to the fifth external terminal and the sixth external terminal with the second switch of the measuring instrument turned off, and the voltage and current of the fifth external terminal at that time are supplied. And the voltage and current of the sixth external terminal to calculate the first estimated value, supply the current to the fifth external terminal with the second switch turned on, and Calculating the second estimated value based on the voltage and current of the external terminal;
In the temperature measurement mode, a current is supplied to the fifth external terminal with the second switch of the measuring instrument turned on, and the third estimation is performed based on the voltage and current of the fifth external terminal at that time. A temperature measurement system, wherein a value is calculated, and a difference between the third estimated value and the wiring resistance value is set to a true value of a resistance value of the temperature measuring resistance element. The temperature measurement system according to claim 6,
An eighth external terminal electrically connected to the fourth external terminal;
The data processing control unit
In the temperature measurement mode, humidity is calculated based on a voltage between the seventh external terminal and the eighth external terminal. 4. A temperature measurement system comprising the temperature detection device according to claim 3 and a measuring instrument having fifth to eighth external terminals, wherein the first to fourth external terminals are connected to the fifth to eighth external terminals as signal lines. Is a temperature measurement method for measuring the temperature in a state where each is connected,
From the voltage and current of the fifth external terminal and the voltage and current of the sixth external terminal when the measuring instrument outputs current from the fifth external terminal and the sixth external terminal, A first step of calculating a first estimated value of the resistance value;
Based on the voltage and current of the fifth external terminal when the measuring instrument outputs a current from the fifth external terminal with the sixth external terminal connected to the ground potential of the measuring instrument, the temperature measurement A second step of calculating a second estimated value of the resistance value of the resistance element;
The measuring instrument connects between the temperature sensing device and the measuring instrument based on a difference between the first estimated value calculated in the first step and the second estimated value calculated in the second step. A third step of calculating a wiring resistance of the signal line;
Based on the voltage and current of the fifth external terminal when the measuring instrument outputs a current from the fifth external terminal with the sixth external terminal connected to the ground potential of the measuring instrument, the temperature measurement A fourth step of calculating a third estimated value of the resistance value of the resistance element;
From the true value of the resistance value of the resistance temperature element obtained by subtracting the wiring resistance calculated in the third step from the third estimated value calculated in the fourth step, the measuring instrument And a fifth step for calculating the temperature.

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