KR20130084520A - An apparatus for measuring temperature with rtd and a method for measuring temperature using it - Google Patents

Abstract

PURPOSE: A temperature measuring apparatus using a resistance temperature detector and a temperature measuring method are provided to adaptively change the circuit configuration by determining the wiring system when measuring the temperature by using the resistance temperature detector, thereby enabling to vary a current supplying path. CONSTITUTION: A temperature measuring apparatus (100) using a resistance temperature detector is comprised of the connection terminals (101,102,103,104), a current supplying unit (150), a detection circuit (110), a plurality of switch (160,170) and a potential difference measuring unit (130). The connection terminals are connected to the resistance temperature detector. The current supplying unit is connected to at least one of the connection terminals and supplies the current to the resistance temperature detector. The detection circuit detects the connection status with the resistance temperature detector by being connected to one of the connection terminals. The plurality of switch is switched to change the current flow between the temperature measuring apparatus and the resistance temperature detector according to the detected connection status. The potential difference measuring unit measures the potential which is generated in both ends of the resistance temperature detector element which is included in the resistance temperature detector by the current flow. [Reference numerals] (110) Pull down; (301,302,303) Internal resistance (r); (350) RTD resistance

Description

Temperature measuring device and temperature measuring method using RTD {AN APPARATUS FOR MEASURING TEMPERATURE WITH RTD AND A METHOD FOR MEASURING TEMPERATURE USING IT}

The present invention relates to a temperature measuring device and a temperature measuring method using a resistance thermometer. More specifically, the circuit configuration is adaptively changed according to the type of the RTD, and relates to a temperature measuring device and a temperature measuring method for reducing the temperature measurement error generated according to the type of the RTD.

Resistance temperature detector element (also called RTD) is a device for sensing temperature by using a platinum sensor or platinum thin film. It is the most stable among the temperature sensors used in the market, and it has high sensitivity and is used for precision temperature measurement. In addition, the linear output of the temperature-resistance is excellent and a linear output can be obtained by a relatively simple additional circuit. Therefore, the RTD can be used in a wide range of precision temperature measurement and control in the future to various household appliances, industrial, automobiles and office while miniaturizing and mass-producing.

The RTD is divided into a metal resistor and a thermistor RTD in terms of material, and since there is a constant relationship between the electric resistance of the metal and the temperature, the temperature can be derived through a proportional increase and decrease of the temperature change caused by the electric resistance. In order to measure temperature with RTD, current flows through metal resistor (RTD element) included in RTD and the voltage at both ends is measured by Ohm's law. It becomes possible. Therefore, the current flowing through the RTD is preferably constant. For example, currents of 2 mA, 5 mA, and 10 mA are currently defined for industrial use.

On the other hand, such a resistance thermometer is a method of measuring the resistance value of the resistance in the circuit configuration in order to measure the temperature through the above-described method, a certain amount of current (constant current supplied from the temperature measuring circuit) flows to the resistance After measuring the voltage at both ends of the resistance, the resistance value can be obtained by calculating the calculated voltage by dividing the measured voltage value by the applied current value. In addition, the sensed temperature may be measured by comparing the found resistance value with respect to the temperature-resistance characteristic table.

However, since resistance exists in the lead wire connected when the RTD and the temperature measuring circuit are connected, the resistance value and the lead resistance of the RTD are included, thereby causing an error in the temperature value measured by the circuit. In order to solve this problem, three-wire wiring resistance thermometer and four-wire wiring resistance thermometer have been proposed to reduce lead resistance.

Figure 1 shows a general temperature measuring device for measuring the temperature by using a four-wire wiring type resistance thermometer.

Referring to FIG. 1, the 4-wire wiring type RTD 20 includes an RTD element 25 and internal resistances 21, 22, 23, and 24 formed by four conductive wires connected to the RTD element 25. The temperature measuring device 10 for measuring the temperature using the same has four connection terminals for connecting the four conductive wires 21, 22, 23, 24 of the RTD and the temperature measuring device 10 ( 11, 12, 13, 14, a constant current supply circuit 18 for supplying a constant current to the RTD 20, a voltage amplifier for amplifying a voltage generated by the flow of current supplied to the RTD 20 ( 16 and 17 and a voltage difference measuring unit 15 for measuring the difference in voltage by measuring the difference between the voltage between the two ends transmitted by the voltage amplifier (16, 17).

As shown in FIG. 1, the current supplied from the constant current supply unit 18 passes through the RTD 25 through the second lead resistance 22 at the second connection terminal 12, and then passes through the third lead resistance 23. ) And the third connection terminal 13 to the ground terminal, whereby voltage is generated at both ends of the RTD 25. Each of the voltage amplifiers 16 and 17 amplifies it, and the voltage difference measuring unit 15 measures the difference between the two voltages. When the measured voltage difference is divided by the supplied constant current value, a resistance value is obtained, and the present temperature can be measured by comparing this with the temperature-resistance characteristic table of the RTD 25.

Figure 2 shows a general temperature measuring device for measuring the temperature by using a three-wire wiring type resistance thermometer.

In FIG. 2, since it is similar to FIG. 1, a detailed description thereof will be omitted. However, since the 3-wire RTD 40 is connected by three conductors, the conducting wire including the first lead resistance 41 of the 3-wire RTD 40 may be connected to the first connection terminal 31 of the temperature measuring device 30. ) And the second connection terminal 31 to measure the temperature.

However, in the case of measuring by such a general temperature measuring method, for the 3-wire wiring type RTD 40, the resistance of the RTD 40 to be measured by the first conductor resistance 41 existing inside the RTD 40 is measured. There is a problem in that an error occurs in the resistance value measured by being connected in series with the resistance of the RTD 45, thereby causing an error in the measurement temperature.

For example, in the case of connecting the 4-wire wired type RTD 20 as shown in FIG. 1, if the current value supplied from the constant current supply unit 18 is i, the current i is generated by the second connection terminal 12 and the conductive wire. It is transmitted to the RTD element 25 via the second internal resistance 22. At this time, no current flows toward the first internal resistor 21 and the fourth internal resistor 24 due to the large input impedance of the voltage amplifiers 16 and 17. Accordingly, the current passing through the RTD 25 flows to the third connection terminal 13 via the third internal resistance 23.

Here, the voltages of the first voltage amplifier 16 and the second voltage amplifier 17 are referred to as V (16) and V (17), respectively, and the resistance value of the RTD element 25 is represented by equation (1). same.

In order to obtain the measured resistance value, the difference in voltage between both ends is obtained as in Equation 2.

By dividing the voltage obtained by the voltage difference measuring unit 15 from the equation (2) by the constant current (i) it can be seen that the RTD to be measured can be accurately obtained.

However, in the case of connecting the three-wire wiring type RTD 40 as shown in FIG.

As a result, even if the final voltage difference is divided by i, it can be seen that an error occurs in the resistance measurement because the wire resistance r inside the sensor remains.

In addition, by using the same circuit configuration for the temperature measurement using the three-wire RTD 20 and the temperature measurement using the four-wire RTD 40, there is a problem in that the temperature measuring device cannot be efficiently used.

SUMMARY OF THE INVENTION An object of the present invention is to provide a temperature measuring device and a temperature measuring method which eliminate a temperature measuring error that may occur according to a wiring method of a resistance thermometer used to solve the above problems.

In addition, the present invention provides a temperature measuring device and a temperature measuring method capable of automatically switching a circuit configuration corresponding to various wiring methods of the RTD.

The present invention also provides a temperature measuring device and a temperature measuring method capable of removing a temperature measuring error by using an amplification factor of a voltage amplifier of a RTD.

A temperature measuring device according to an embodiment of the present invention for achieving the above object, the temperature measuring device for measuring the temperature using a resistance thermometer, at least one connection terminal for connecting with the resistance thermometer; A current supply unit connected to at least one of the connection terminals and configured to supply current to the RTD; A sensing circuit connected to any one of the one or more connection terminals to sense a connection state with the RTD; A plurality of switches switched to change a current flow between the temperature measuring device and the RTD according to the sensed connection state; And a voltage difference measurer configured to measure a voltage difference generated at both ends of the RTD included in the RTD by the current flow.

In addition, the temperature measuring method according to an embodiment of the present invention for achieving the above object, the method for measuring the temperature by the temperature measuring device using the RTD, the step of connecting the RTD and the temperature measuring device; Determining a driving mode according to the connection state; Controlling a plurality of switches included in the internal circuit of the temperature measuring device according to the determined operation mode; Supplying current to the connected RTD; And measuring a voltage difference across the RTD generated by the supplied current.

According to the exemplary embodiment of the present invention, when measuring the temperature using the RTD, the current supply path can be varied by adaptively changing the circuit configuration by determining the wiring method.

In addition, the circuit configuration is changed according to the wiring method of the RTD or the type of the RTD, thereby providing a temperature measuring apparatus and a temperature measuring method capable of eliminating a measurement error caused by the wiring change.

In particular, by varying the amplification factor of the voltage amplifier according to the wiring method of the RTD or the type of the RTD, the error is eliminated, thereby improving accuracy and providing an efficient temperature measuring device and a temperature measuring method.

Figure 1 shows a general temperature measuring device for measuring the temperature by using a four-wire wiring type resistance thermometer.
Figure 2 shows a general temperature measuring device for measuring the temperature by using a three-wire wiring type resistance thermometer.
3 is a view showing an operation when the temperature measuring device according to an embodiment of the present invention is connected to a 4-wire RTD.
FIG. 4 is a view illustrating a change in the connection state when the temperature measuring device according to an embodiment of the present invention is connected to a 3-wire RTD.
5 is a view showing an operation when the temperature measuring device according to an embodiment of the present invention is connected to a 3-wire RTD.
6 and 7 are flowcharts illustrating a mode change process in the temperature measuring method according to an embodiment of the present invention.

The following merely illustrates the principles of the invention. Thus, those skilled in the art will be able to devise various apparatuses which, although not explicitly described or shown herein, embody the principles of the invention and are included in the concept and scope of the invention. Furthermore, all of the conditional terms and embodiments listed herein are, in principle, intended only for the purpose of enabling understanding of the concepts of the present invention, and are not intended to be limiting in any way to the specifically listed embodiments and conditions .

It is also to be understood that the detailed description, as well as the principles, aspects and embodiments of the invention, as well as specific embodiments thereof, are intended to cover structural and functional equivalents thereof. It is also to be understood that such equivalents include all elements contemplated to perform the same function irrespective of the currently known equivalents as well as the equivalents to be developed in the future, i.e., the structure.

Thus, for example, it should be understood that the block diagrams herein represent conceptual views of exemplary circuits embodying the principles of the invention. Similarly, all flowcharts, state transition diagrams, pseudo code, and the like are representative of various processes that may be substantially represented on a computer-readable medium and executed by a computer or processor, whether or not the computer or processor is explicitly shown .

The functions of the various elements shown in the figures, including the functional blocks depicted in the processor or similar concept, may be provided by use of dedicated hardware as well as hardware capable of executing software in connection with appropriate software. When provided by a processor, the functions may be provided by a single dedicated processor, a single shared processor, or a plurality of individual processors, some of which may be shared.

Also, the explicit use of terms such as processor, control, or similar concepts should not be interpreted exclusively as hardware capable of running software, and may be used without limitation as a digital signal processor (DSP) (ROM), random access memory (RAM), and non-volatile memory. Other hardware may also be included.

In the claims of this specification, components expressed as means for performing the functions described in the detailed description include all types of software including, for example, a combination of circuit elements or firmware / microcode, etc. that perform the functions. It is intended to include all methods of performing a function which are combined with appropriate circuitry for executing the software to perform the function. The invention, as defined by these claims, is equivalent to what is understood from this specification, as any means capable of providing such functionality, as the functionality provided by the various enumerated means are combined, and in any manner required by the claims. It should be understood that.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings, in which: There will be. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3 is a view showing an operation when the temperature measuring device according to an embodiment of the present invention is connected to a 4-wire RTD.

Referring to FIG. 3, when the RTD 200 is a 4-wire wire, the temperature measuring device 100 according to an exemplary embodiment of the present invention may include a first connection terminal 101 and a second connection to be connected to each wire. A current supply unit 150 connected to the terminal 102, the third connection terminal 103, and the fourth connection terminal 104 and at least one pair of the connection terminals to supply a current to the RTD 200. ), A first voltage amplifier 120, a second voltage amplifier 141 and a third voltage amplifier 142 for amplifying the voltage across the RTD 200 generated by the supplied current, and according to the amplified voltage. A voltage difference measuring unit 130 for measuring a voltage difference, a temperature output unit 190 for outputting a temperature corresponding to the measured voltage, a sensing circuit 110 for detecting a connection state of a connection terminal, and the detected connection Control of the controller 180 and the controller 180 for changing the driving mode by determining the connection state according to the state It is switched by is configured to include a first switch 160 and second switch 170 for changing the current flow in accordance with the operation mode.

Each of the four connection terminals includes a first connection terminal 101, a second connection terminal 102, a third connection terminal 103, and a fourth connection terminal 104, and each of the four-wire RTDs 200. It is configured to connect to the line.

In addition, the lead resistance of each wire of the 4-wire RTD 200 connected to the temperature measuring device 100 may be divided into four internal resistances. That is, the 4-wire RTD 200 includes a RTD element 250, a first internal resistance 201, a second internal resistance 202, a third internal resistance 203, and a fourth internal resistance 204. Can be configured.

First, the sensing circuit 110 may be configured as, for example, a pull-down circuit or a pull-up circuit to detect whether the 4-wire RTD is connected.

When the 4-wire RTD is connected, the controller 180 controls the first switch 160 and the second switch 170 in the 4-wire mode. In 4-wire mode, switch operation is as follows.

In the 4-wire mode as shown in FIG. 3, the first switch 160 connects the second connection terminal 102 and the current supply unit 150, and separates the first connection terminal 101 and the current supply unit 150. The second switch 170 connects the second voltage amplifier 141 and the voltage difference measuring unit 130, and separates the third voltage amplifier 142 and the voltage measuring unit 130. When switched in this way, current flows from the current supply unit 150 through the second connection terminal 102 and through the RTD 250 to the ground terminal through the third connection terminal 103 again. do. In addition, a current does not flow in the first connection terminal 101 and the fourth connection terminal 104 due to the high impedance of each voltage amplifier, and the voltage at both ends of the RTD element 250 is applied as it is.

Accordingly, the first voltage amplifier 120 and the second voltage amplifier 141 amplify each of the applied voltages and input them to the voltage difference measurement unit 130, and the voltage difference measurement unit 130 measures the difference between the amplified voltages at both ends. The resistance value is calculated and transmitted to the temperature output unit 190.

The temperature output unit 190 converts the resistance value calculated by the voltage difference measurement unit 130 into a temperature value with reference to the temperature-resistance characteristic table, and outputs the converted temperature value to the outside.

When the 4-wire wiring RTD 200 is connected as shown in FIG. 3, the voltage across the RTD element 250 of the RTD 200 is generated according to the flow of current when the 4-wire wiring RTD 200 is connected. Since the internal resistance is not taken into account in the temperature calculation, accurate temperature can be measured.

4 is a diagram illustrating a case where the 3-wire wiring resistance thermometer 300 is connected while operating in the 4-wire mode.

On the other hand, when the 3-wire wiring RTD 300 is connected while the temperature measuring device 100 operates in the 4-wire mode as shown in FIG. 4, no wire is connected to the second connection terminal 102. In this case, the current flowing through the current supply unit 150 and the first switch 160 prevents the current from flowing because the second connection terminal 102 is opened. In addition, when the sensing circuit 110 connected to the first connection terminal 101 is a pull-down circuit, a negative voltage (−) is applied to the first voltage amplifier 120 and a zero potential is applied to the second voltage amplifier 141. (Ground potential) is applied, and the measured voltage difference of the voltage difference measuring unit 130 becomes a negative voltage.

Therefore, when the three-wire wiring RTD 300 is connected during the four-wire mode operation as shown in FIG. 4, the change or change of the connection state may be detected by the sensing circuit or the voltage difference measuring unit 130. That is, when the sensing circuit operates due to the interruption of the current supply to the second connection terminal 102 or when the polarity of the voltage difference measuring unit 130 is changed by the sensing circuit, the connection state may be detected.

On the other hand, since the temperature measurement is impossible when connected as shown in Figure 4, the controller 180 can control to switch to the three-wire mode by controlling the switch. In addition, the controller 180 may control to operate in a three-wire or four-wire mode even before connecting the RTD according to the user's setting, and of course, by setting a separate wiring check mode, connected before the current supply Only the state may be detected in advance and it may be determined whether the wiring is three or four wires.

5 is a view showing that the temperature measuring device according to an embodiment of the present invention operates in the 3-wire mode when connected to the 3-wire RTD.

As shown in FIG. 5, when the 3-wire RTD 300 is connected, the temperature measuring device according to an exemplary embodiment of the present invention may be switched under the control of the controller 180 to be changed to the 3-wire mode. .

Description of each component is as described above with reference to FIGS. 3 and 4. However, in the present exemplary embodiment, the first switch 160 and the second switch 170 are changed to the three-wire mode of the controller 180. There is a difference in that the switching in the other direction than in FIG. This will be described in detail as follows.

The first switch 160 connects the first connection terminal 101 and the current supply unit 150, and separates the second connection terminal 102 and the current supply unit 150.

The second switch 170 separates the second voltage amplifier 141 and the voltage difference measurement unit 130, and connects the third voltage amplifier 142 and the voltage difference measurement unit 130. Here, the amplification rate of the third voltage amplifier 142 may be twice the amplification rate of the second voltage amplifier 141. The above-described measurement error may be eliminated by the difference in amplification factor, which will be described later.

When operating in the 3-wire mode as shown in FIG. 5, current flows from the current supply unit 150 to the first input terminal 101 through the first switch 160. The first input terminal 101 is connected to the first internal resistance 301 which is one of the lead resistances of the 3-wire RTD 300, and a current is input to the RTD 350 through the path. The current passing through the RTD 350 flows through the second internal resistor 302 to the ground terminal through the third input terminal 103.

The voltage difference measured by the voltage difference measurement unit 130 by the current flowing in the configuration as shown in FIG. 5 may be calculated as follows.

First, when the voltage of the first voltage amplifier 120 is V 120, V 120 is represented by Equation 4 below.

Here, i represents the magnitude of the current, r represents the internal resistance, and RTD represents the resistance of the three-wire RTD element 350.

And, if the output voltage of the third voltage amplifier 142 is V (142), the equation for this is as shown in Equation 5 below.

The reason why V 142 is the same as Equation 5 is because a current does not flow in the third internal resistor 303 connected to the RTD 300 due to the high impedance of the third voltage amplifier 142, and thus there is no voltage drop. to be.

On the other hand, the voltage difference measured by the voltage difference measuring unit 130 is calculated by the following equations (4) and (5).

Therefore, when the voltage difference measured by the voltage difference measuring unit 130 is divided by the input current value i of the current supply unit 150 as shown in Equation 6, the resistance RTD of the RTD 350 can be accurately obtained without error. It can be seen.

As described above, according to the temperature measuring device of the present invention, the operation mode can be changed according to the type and wiring of the RTD by detecting the 3-wire or 4-wire mode according to the connection state, and the temperature measurement error can be eliminated even in the 3-wire mode. As a result, accurate temperature can be measured without affecting the internal resistance of the RTD.

6 is a flowchart illustrating a mode change process in the temperature measuring method according to an exemplary embodiment of the present invention.

Referring to FIG. 6, first, the sensing circuit 110 or the controller 180 detects a connection state based on a voltage or current state of each connection terminal (S100). In FIG. 6, it is assumed that the connection state is basically a state in which the 4-wire RTD 200 is connected. Accordingly, the controller 180 operates the first switch 160 and the second switch 170 of the temperature sensing device in the four-wire mode according to the sensing result.

Then, as described above, it is checked whether the connection state is changed based on the voltage current state of each connection terminal (S110). In addition, even when the connection state is not changed, when operating in the wiring check mode by user setting or the like, it is possible to reconfirm whether there is a change in the current connection state.

If the connection state is not changed, the four-wire mode is operated as it is.

However, when it is determined that the connection state is changed, the voltage difference measuring unit 120 measures the voltage difference (S120), and determines whether the voltage polarity of the measured voltage difference has a negative voltage (S130). As described above, in the case of having a negative voltage, as shown in FIG. 4, it may be determined that the 3-wire RTD 300 is connected during the 4-wire mode operation.

Therefore, when the voltage polarity is not the negative voltage, the four-wire mode may be maintained as it is, but in the case of the negative voltage, the controller 180 changes to the three-wire mode to measure the voltage without error (S140).

7 is a flowchart illustrating a voltage measuring method according to an embodiment of the present invention as a whole.

Referring to FIG. 7, first, the RTD and the temperature measuring device 100 are connected (S200). In the 4-wire mode, the conductive wires of the corresponding RTDs are connected to the four connection terminals of the temperature measuring device 100, and in the 3-wire mode, the first connection terminal of the connection terminals of the temperature measuring device 100 ( 101, the third connecting terminal 103 and the fourth connecting terminal 104 may be connected to the corresponding conductive wire, respectively.

Thereafter, the controller 180 detects a connection state through the detection circuit 110 (S210). As a result of the detection by the sensing circuit 110, the controller 180 may detect a connection state or the controller 180 itself may detect an input / output current to detect the connection state. In addition, the sensing circuit 110 may output a sensing result. The sensing circuit 110 may be configured as a pull-down circuit or a pull-up circuit so that different outputs are generated according to current or voltage input and output.

The controller 180 determines a driving mode according to the detected connection state. If it is determined that the four-wire mode is to control the operation of the first switch 160 and the second switch 170 to correspond to the four-wire mode (S230). In the 4-wire mode, the current flows through the RTD 200 through the second input terminal 102 to the third input terminal 103 according to the operation of the switch.

On the other hand, if it is determined that the three-wire mode is the three-wire mode, the controller 180 controls the operation of the first switch 160 and the second switch 170 (S225). In the 3-wire mode, current flows through the RTD 200 through the first input terminal 102 to the third input terminal 103 according to the operation of the switch.

Then, the current supply unit 150 supplies a constant current so that the current flow as described above (S240). The magnitude of the constant current supplied is an allowable current meeting the RTD standard, and may be any one of industrially specified currents of 2 mA, 5 mA, and 10 mA. Also, it may be 1 mA, which is a standard current.

In addition, the first voltage amplifier 120, the second voltage amplifier 141, or the third voltage amplifier 142 amplifies the voltages at both ends of the RTD generated by the supply of current to the voltage difference measuring unit 130. (S250).

Thereafter, the voltage difference measuring unit 260 measures the voltage difference and transmits the measured voltage difference to the temperature output unit 190 (S270). The voltage difference measuring unit 260 may derive the resistance value of the RTD by dividing the measured voltage difference by a current supply value.

The temperature output unit 190 compares the temperature-resistance element temperature-resistance table of the RTD based on the voltage difference or resistance measured by the voltage difference measurement unit 260 and outputs a corresponding temperature value to the outside (S270). .

By such a temperature measuring method, it is possible to detect the RTD connection state and measure the temperature according to the operation mode corresponding thereto, and to provide a temperature measuring method that can reduce the error even if the connection state is changed.

The above-described temperature measuring method according to the present invention can be stored in a computer-readable recording medium that is produced as a program for execution on a computer, and examples of the computer-readable recording medium include ROM, RAM, CD-ROM, Magnetic tapes, floppy disks, optical data storage devices, and the like, and also include those implemented in the form of carrier waves (eg, transmission over the Internet).

The computer readable recording medium may be distributed over a networked computer system so that computer readable code can be stored and executed in a distributed manner. And, functional programs, codes and code segments for implementing the above method can be easily inferred by programmers of the technical field to which the present invention belongs.

In addition, although the preferred embodiment of the present invention has been shown and described above, the present invention is not limited to the specific embodiments described above, but the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Of course, various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or prospect of the present invention.

100: temperature measuring device 101: first connection terminal
102: second connection terminal 103: third connection terminal
104: fourth connection terminal 110: sensing circuit
120: first voltage amplifier 130: voltage difference measuring unit
141: second voltage amplifier 142: third voltage amplifier
150: current supply unit 160: first switch
170: second switch 180: control unit
190: temperature output unit 200: 4-wire RTD
250: 4-wire RTD 300: 3-wire RTD
350: 3-wire RTD element

Claims (14)

In the temperature measuring device for measuring the temperature using a resistance thermometer,
One or more connection terminals for connecting with the RTD;
A current supply unit connected to at least one of the connection terminals and configured to supply current to the RTD;
A sensing circuit connected to any one of the one or more connection terminals to sense a connection state with the RTD;
A plurality of switches switched to change a current flow between the temperature measuring device and the RTD according to the sensed connection state; And
And a voltage difference measurer configured to measure a voltage difference generated at both ends of the RTD included in the RTD by the current flow. The method of claim 1,
And at least one voltage amplifier connected to both ends of the voltage difference measuring unit and configured to amplify a voltage generated by a current supplied to the RTD. The method of claim 1,
Further comprising a control unit for controlling the plurality of switches,
The control unit is a temperature measuring device for controlling the plurality of switches to switch to the three-wire mode or four-wire mode according to the detected connection state. The method of claim 1,
And a temperature output unit configured to convert the voltage difference measured by the voltage difference measuring unit into a measurement temperature and output the measured temperature difference. The method of claim 1,
The sensing circuit includes a pull-down circuit, the temperature measuring device for detecting the connection state based on the polarity of the voltage across the voltage difference measuring unit. The method of claim 5,
And the plurality of switches are switched to a three wire mode or a four wire mode according to the polarities of the voltages at both ends. The method of claim 1,
A first switch connected to one end of the voltage difference measuring unit; And
Further comprising a first voltage amplifier and a second voltage amplifier connected to the first switch,
And the amplification factor of the second voltage amplifier is twice the amplification factor of the first voltage amplifier. The method of claim 7, wherein
And the first switch is switched to connect the first voltage amplifier or the second voltage amplifier and the voltage difference measuring unit according to the sensed connection state. In the method in which the temperature measuring device measures the temperature using a resistance thermometer,
Connecting the RTD and the temperature measuring device;
Determining a driving mode according to the connection state;
Controlling a plurality of switches included in the internal circuit of the temperature measuring device according to the determined operation mode;
Supplying current to the connected RTD; And
And measuring a voltage difference across the RTD generated by the supplied current. 10. The method of claim 9,
Amplifying the voltage across the RTD. The method of claim 10,
And the amplification factor of the voltage at one end of the RTD is twice the amplification factor of the voltage at the other end of the RTD. 10. The method of claim 9,
The operation mode is a temperature measurement method, characterized in that the three-wire mode or four-wire mode according to the type of the RTD. 10. The method of claim 9,
And converting the measured voltage difference to output a temperature value. 10. The method of claim 9,
The determining of the driving mode according to the connection state
Detecting the connection state based on polarities of voltages between the voltage difference measuring units; And
Determining a three-wire or four-wire mode according to the connection state.

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