WO2011131077A1

WO2011131077A1 - Measurement system for thermal resistance signals

Info

Publication number: WO2011131077A1
Application number: PCT/CN2011/072328
Authority: WO
Inventors: 王常力; 史洪源; 周有铮; 虞日跃
Original assignee: 杭州和利时自动化有限公司
Priority date: 2010-04-20
Filing date: 2011-03-31
Publication date: 2011-10-27
Also published as: CN101806640B; CN101806640A

Abstract

A measurement system for thermal resistance signals comprises a first constant current source (I1), a second constant current source (I2), a flying capacitor (Cf), an analog/digital converter (32), a precision resistor (Rref), a controller (33), a charging control unit (30) arranged between the flying capacitor (Cf) and a thermal resistor (Rt) and connected with the first constant current source (I1) and the second constant current source (I2), and a connecting control unit (31) arranged between the analog/digital converter (32) and the flying capacitor (Cf). The measurement system can improve the accuracy of thermal resistance signal measurement.

Description

Thermoelectric P signal measuring system

The present application claims priority to Chinese Patent Application No. 20101015309, filed on Apr. 20, 2010, the entire disclosure of which is incorporated herein by reference. in.

Technical field

The present invention relates to the field of industrial automation control technology, and more particularly to a measurement system for a thermal resistance signal.

Background technique

Thermistor is a common temperature measuring device in the field of industrial automation, and its resistance value (ie, thermistor signal) changes with temperature. The measurement system measures the temperature by measuring the resistance value.

Generally, the two-wire system, the three-wire system or the four-wire system can be connected between the thermal resistance and the measuring system. However, in practical applications, the distance between the thermal resistance and the measuring system is long, and the wires connecting the two are long. The two-wire connection method will affect the measurement accuracy by the wire resistance, and the four-wire connection method will increase the wire cost, so the three wires The connection method is commonly used. When using the three-wire connection method, the measurement system generally converts the thermal resistance signal into a voltage signal by a bridge method or a single constant current source method, and then converts the voltage signal into a digital signal through an A/D converter (analog/digital converter). Send to controller.

The thermal resistance signal measuring system illustrated in Figures 1 and 2 is commonly used in the prior art. Among them, Figure 1 is a schematic diagram of the system circuit using the bridge method to measure the thermal resistance signal. The thermal resistance Rt is connected to the measuring system via three wires. The precision resistors Rl, R2 and R3 in the measuring system and the thermal resistor form a Wheatstone bridge. The reference provides a constant voltage excitation to the bridge. When the thermal resistance signal changes, the output voltage of the bridge (ie, the input voltage of the A/D converter) changes, and the voltage signal is converted to a digital signal by the A/D converter and sent to the controller, thereby realizing the thermal resistance signal. Measurement.

Figure 2 is a schematic diagram of a system circuit for measuring the thermal resistance signal using a single constant current source method. The thermal resistance Rt is connected to the measurement system via three wires. The constant current source supplies a constant current through the thermal resistor Rt to generate a voltage signal proportional to the resistance of the thermal resistor. The voltage signal is converted into a digital signal by the A/D converter and sent to the controller to realize the thermal resistance signal. measuring.

However, the inventors' research found that the existing two methods of measuring the thermal resistance signal have at least the following defects: (1) Disadvantages of the bridge method:

There is no linear relationship between the output voltage of the bridge and the RTD signal, so there is a nonlinear error in the measurement;

When there is a common mode interference voltage across the thermal resistor, the output voltage of the bridge will contain the components of the common mode interference voltage, which will reduce the measurement accuracy. Therefore, the measurement method has poor anti-common mode interference capability.

(2) Disadvantages of the single constant current source method:

In order not to affect the measurement accuracy of the system by the resistance of the wire, a special wire-blocking circuit is required, which increases the cost of the system;

The measurement accuracy of the system depends on the accuracy of the constant current source, so the performance requirements of the constant current source are high. It can be seen that the prior art method for measuring the resistance of the thermal resistance generally has the problems of low measurement accuracy and poor accuracy.

Summary of the invention

In view of this, embodiments of the present invention provide a measurement system for a thermal resistance signal to improve the accuracy of measuring a thermal resistance signal.

Embodiments of the present invention provide a measurement system for a thermal resistance signal, the system comprising: a first constant current source and a second constant current source, a flying capacitor, an analog to digital converter, a precision resistor, a controller, and the a charging control unit between the flying capacitor and the thermal resistor and connecting the first constant current source and the second constant current source, and a connection control unit disposed between the analog/digital converter and the flying capacitor;

The thermal resistance is connected by a three-wire method, the lead includes a first lead, a second lead, and a third lead, wherein the third lead is grounded; the thermal resistor passes through the first lead, the second Lead wires, respectively connected to the first plate and the second plate of the flying capacitor through the charging control unit;

The charging control unit is configured to perform charging a first time on the flying capacitor in a first charging cycle, and performing a second charging on the flying capacitor in a second charging cycle;

The connection control unit is configured to connect the analog/digital converter and the first and second plates of the flying capacitor after the first charging and the second charging are respectively ended, The analog/digital converter converts the voltage signal stored between the flying capacitor plates into a first digital signal and a second digital signal; the first end of the precision resistor is grounded, and the second end is connected to the analog/digital converter And the precision The second end of the resistor is connected to the first constant current source and the second constant current source through the charging control unit, and the charging control unit is further configured to control the first constant current source and the second constant current source The output current is combined to flow through the precision resistor to provide a reference voltage for the analog to digital converter;

The controller is configured to obtain a final measurement result of the thermal resistance signal according to the first digital signal and the second digital signal.

Preferably, the charging control unit comprises:

a first switch disposed between the first constant current source and the first plate of the flying capacitor, and a second switch disposed between the second constant current source and the second plate of the flying capacitor; When the first switch and the second switch are closed, the first constant current source and the second constant current source perform the first charging of the flying capacitor;

a third switch disposed between the first constant current source and the second plate of the flying capacitor, and a fourth switch disposed between the second constant current source and the first plate of the flying capacitor; When the three switches and the fourth switch are closed, the first constant current source and the second constant current source perform a second charging on the flying capacitor;

And a fifth switch connected between the first constant current source and the second constant current source, connected to the first constant current source, and a sixth switch connected to the second constant current source; When the five switches and the sixth switch are closed, the currents output by the first constant current source and the second constant current source are combined to flow through the precision resistor to provide a reference voltage for the analog/digital converter.

Preferably, the system further includes:

a seventh switch connected to the first switch on the first lead; an eighth switch connected to the second switch on the second lead; and being disposed on the third lead Connect the ninth switch at the ground.

Preferably, the system further includes:

a first switch connecting the first switch and the first plate of the flying capacitor, and a fourth switch connecting the fourth switch and the first plate of the flying capacitor, and connecting the second switch and the a second plate of the flying capacitor and an eleventh switch connecting the third switch and the second plate of the flying capacitor.

Preferably, the connection control unit includes: a first plate disposed on the flying capacitor and the module

A twelfth switch between the /digital converters, and a thirteenth switch disposed between the second plate of the flying capacitor and the analog to digital converter.

Preferably, the system further includes: a unity gain amplifier, a forward input of the unity gain amplifier is connected to the twelfth switch, a negative input of the unity gain amplifier is connected to an output, and the output is connected to the analog/digital converter.

Preferably, the unity gain amplifier is an operational amplifier, and the leakage current of the flying capacitor is maintained at a measurement accuracy during a time when the analog/digital converter converts a voltage signal stored by the flying capacitor. Within the scope of the request.

Preferably, the current values of the first constant current source and the second constant current source are equal.

Preferably, the switch is an analog switch.

Compared with the prior art, the technical solution provided by the present invention charges the flying capacitor twice by the first constant current source and the second constant current source, so that the final measurement result is independent of the wire resistance, and the wire resistance can be eliminated. And the measurement result is proportional to the thermal resistance signal, so the measurement method of the invention has no nonlinear error;

Secondly, the reference voltage of the analog-to-digital converter is provided by a precision resistor, which can eliminate the influence of the accuracy of the constant current source on the measurement result;

In addition, when there is common mode interference at both ends of the thermal resistor, the interference voltages of the same magnitude and direction are superimposed on both ends of the thermal resistor, and the flying capacitor is charged twice during the charging process by the first constant current source and the second constant current source. The two ends of the thermal resistor are respectively connected to the two ends of the flying capacitor, so the interference voltage signal is not stored on the flying capacitor Cf. Therefore, the measuring system of the thermistor signal provided by the invention has strong anti-common-mode interference capability.

DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments or the description of the prior art will be briefly described below. Obviously, the drawings in the following description are only the present invention. In some embodiments, other drawings may be obtained from those of ordinary skill in the art in light of the inventive work.

1 is a schematic diagram of a system circuit for measuring a thermal resistance signal by a bridge method in the prior art; FIG. 2 is a schematic diagram of a system circuit for measuring a thermal resistance signal by a single constant current source method in the prior art; FIG. 3 is an implementation of the present invention; FIG. 4 is a schematic circuit diagram of a system for realizing single channel thermal resistance signal measurement according to an embodiment of the present invention; FIG. FIG. 5 is a schematic circuit diagram of a system for implementing multi-channel thermal resistance signal measurement according to an embodiment of the present invention.

The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. example. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without the creative work are all within the scope of the present invention.

In order to avoid the problem that the measurement accuracy is low and the accuracy is poor in the existing thermal resistance signal measurement method, the embodiment of the invention provides a non-linear error, and the measurement accuracy is not affected by the wire resistance and the constant current source accuracy, and is resistant to the common A new type of system for measuring thermal resistance signals with strong mode interference capability.

First, the measurement system of the thermistor signal provided by the present invention will be described first. Referring to FIG. 3, the system includes: a first constant current source II and a second constant current source 12, a flying capacitor Cf, and an analog/digital (A/). D) a converter, a precision resistor Rref, a controller 33, a charging control unit 30 disposed between the flying capacitor and the thermal resistor and connecting the first constant current source II and the second constant current source 12, and a charging device a connection control unit 31 between the analog/digital converter and the flying capacitor Cf;

The thermal resistance Rt is connected by a three-wire method, the lead includes a first lead, a second lead, and a third lead, wherein the third lead is grounded (as indicated by point C); the thermal resistor Rt passes through a first lead, a second lead, and a first plate and a second plate respectively connected to the flying capacitor Cf via the charging control unit 30;

The charging control unit 30 is configured to charge the flying capacitor Cf for a first time in a first charging cycle, and perform a second charging of the flying capacitor Cf in a second charging cycle;

The connection control unit 31 is configured to connect the first and second plates of the analog/digital converter and the flying capacitor Cf after the first charging and the second charging are respectively completed, so that An analog/digital converter converts a voltage signal stored between the two capacitor plates of the flying capacitor Cf into a first digital signal and a second digital signal;

The first end of the precision resistor Rref is grounded, the second end is connected to the analog-to-digital converter, and the second end of the precision resistor Rref is connected to the first constant current source II through the charging control unit 30. a second constant current source 12, wherein the charging control unit 30 is further configured to control the first constant current source II and the second The current outputted by the constant current source 12 is combined to flow through the precision resistor Rref to provide a reference voltage for the analog/digital converter;

The controller 33 is configured to obtain a final measurement result of the thermal resistance Rt signal according to the first digital signal and the second digital signal.

The technical solution provided by the present invention charges the flying capacitor twice by the first constant current source and the second constant current source, so that the final measurement result is independent of the wire resistance, and the influence of the wire resistance on the measurement result can be eliminated; and, the measurement result It is proportional to the thermal resistance signal, so the measurement method of the present invention has no nonlinear error;

In an embodiment of the present invention, the charging control unit may adopt the following implementation manners: including a first switch S1 disposed between the first constant current source II and the first plate of the flying capacitor Cf, and disposed at the a second switch S2 between the second constant current source 12 and the second capacitor of the flying capacitor Cf; when the first switch S1 and the second switch S2 are closed, the first constant current source II and the second constant The flow source 12 performs the first charging of the flying capacitor Cf;

a third switch S3 disposed between the first constant current source II and the second plate of the flying capacitor Cf, and a fourth switch disposed between the second constant current source 12 and the first plate of the flying capacitor Cf S4; when the third switch S3 and the fourth switch S4 are closed, the first constant current source II and the second constant current source 12 perform a second charging on the flying capacitor Cf;

And a fifth switch S5 connected between the first constant current source II and the second constant current source 12, connected to the first constant current source, and a sixth switch S6 connected to the second constant current source When the fifth switch S5 and the sixth switch S6 are closed, the currents output by the first constant current source II and the second constant current source 12 are combined and flow through the precision resistor Rref for the analog/digital conversion. The reference voltage is supplied. In order to facilitate the connection and disconnection of the thermal resistor Rt and the measuring system, those skilled in the art can add the following settings in the measuring system shown in FIG. 3: for example: being disposed on the first lead and the first switch a switch K11 connected to the second lead and a switch K21 connected to the second switch; and a switch K31 disposed at a ground end of the third lead. The connection and disconnection of the thermal resistance Rt from the measurement system is achieved by controlling the conduction and disconnection of the switches K11, K21 and K31.

Similarly, in order to facilitate the connection between the flying capacitor Cf and the charging control unit, in other preferred embodiments of the present invention, the following connection manner may be adopted between the flying capacitor Cf and the charging control unit: by connecting the first switch and the a first plate of the flying capacitor, a tenth switch S10 connecting the fourth switch and the first plate of the flying capacitor, and a second plate connecting the second switch and the flying capacitor And connecting the third switch and the eleventh switch S11 of the second plate of the flying capacitor. When the first constant current source II and the second constant current source 12 charge the flying capacitor Cf through the thermal resistor Rt, the switches S10 and S11 are both closed.

It should be noted that the connection control unit may also adopt a switch implementation, and specifically includes: a switch S12 disposed between the first plate of the flying capacitor and the analog/digital converter, and configured to be disposed on a switch S13 between the second plate of the flying capacitor and the analog/digital converter.

Generally, in the process of analog-to-digital conversion of the voltage signal generated by the analog-to-digital converter on the flying capacitor Cf, the flying capacitor Cf generates a leakage current through the analog-to-digital converter. To meet the accuracy requirement, the leakage current needs to satisfy a certain amount. The numerical limit. By setting a unity gain amplifier between the flying capacitor Cf and the analog-to-digital converter, and keeping the input bias current within a certain range, the charge stored on the flying capacitor Cf is generated in the analog-to-digital conversion time. The leakage current is maintained within the range allowed by the measurement accuracy. The positive input terminal of the unity gain amplifier is connected to the switch S12, and the negative input terminal of the unit gain amplifier is connected to the output terminal, and the output terminal is connected to the analog/digital converter. Preferably, the unity gain amplifier may be an operational amplifier.

In addition, in order to realize the transmission of analog signals such as voltage and current, all of the above switches are analog switches.

In order to facilitate a further understanding of the present invention, the invention will be described in detail below with reference to the specific embodiments of the invention. 4 is a schematic circuit diagram of a system for realizing single-channel thermal resistance signal measurement according to the present invention. The resistance values of the three wires connected to the thermal resistance Rt are the same, and both are RL. For the sake of clarity, the resistance RL represents the resistance of the wire.

The measuring system consists of the following parts: analog switches K11, K21 and K31 for switching the Rt channel of the RTD, constant current sources II and 12 with the same current value, analog switches S1~S5 for switching the constant current source, flying Capacitor Cf, analog switches S9 and S10 for connecting flying capacitors and current sources, unity gain amplifier U1, A/D converter, analog switch S11 for connecting flying capacitors and unity gain amplifiers, for connecting flying capacitors and A The analog switch S12 of the /D converter and the precision resistor Rref for providing the reference voltage of the A/D converter.

When measuring the RTD signal using the above system, the measurement method is described as follows:

When the system is in the initial state, all analog switches are in the off state;

Close the analog switches Kl l , K21 and K31 that switch the RTD channel so that the three wires of the RTD are connected to the E, S and C points of the measuring system, respectively, so that Rt is connected to the measuring system. At the same time, the switches S1 and S2 are closed, the constant current source II is connected with the E point, the constant current source 12 is connected with the S point; the switches S9 and S10 are closed, and the upper plate of the flying capacitor Cf is connected with the E point, the lower plate and the S Point connection. At this time, the constant current sources II and 12 start to charge the flying capacitor Cf for the first time through the thermal resistance Rt;

After the first charge is completed, the voltage stored on the flying capacitor Cf is Vfl. Disconnect the switches K11, Κ21, K31, Sl, S2, S10 and S11; Close the switches S12 and S13 to connect the flying capacitor Cf to the A/D converter through the unity gain amplifier U1; and simultaneously close the switches S5 and S6 to make the constant current Sources II and 12 combine to flow through the precision resistor Rref to provide a reference voltage for the A/D converter. The A/D converter performs analog-to-digital conversion on the voltage signal Vfl stored on the flying capacitor Cf, and outputs the obtained first digital signal to the controller;

After the analog-to-digital conversion is complete, close switches K11, K21, and K31 to connect Rtl to the measurement system again. At the same time, unlike the first charging process, the switches S3 and S4 are closed, the constant current source II is connected to the S point, and the constant current source 12 is connected to the E point; the switches S10 and S11 are closed to make the flying capacitor Cf upper plate Connected to point E, the lower plate is connected to point S. The constant current sources II and 12 again start to charge the flying capacitor Cf a second time through the thermal resistor Rt;

After the second charging is completed, the voltage stored on the flying capacitor Cf is Vf2. The switches K11, Κ21, Κ31, S3, S4, S10 and S11 are turned off. Close the switches S12 and S13, so that the flying capacitor Cf is connected to the A/D converter through the unity gain amplifier U1; at the same time, the switches S5 and S6 are closed, and the constant current sources II and 12 are combined to flow through the precision. The resistor Rref provides a reference voltage for the A/D converter. The A/D converter performs analog-to-digital conversion on the voltage signal Vf2 stored on the flying capacitor Cf, and outputs the obtained second digital signal to the controller;

The controller processes the digital signals converted by the two analog-to-digital conversions, and averages the results of the two digital signals, which is the final measurement result of the thermal resistance signal of the channel.

The above embodiment uses the measurement system provided by the present invention to measure the signal of the thermal resistance Rt in a single channel. Of course, the technical solution of the present invention is equally applicable to the signal measurement of the thermal resistance in the n channel. Similarly, the thermal resistance Rtl~Rtn in the multi-channel is connected to the measurement system through a three-wire system, as shown in Figure 5.

To measure the RTD signal of the other channels, repeat the measurement steps in the above single channel. In the above measurement system, according to the measurement accuracy requirement, by selecting a suitable operational amplifier as the unity gain amplifier U1 and keeping its input bias current within a certain range, the charge stored on the flying capacitor Cf can be converted in analog to digital. The leakage current generated during the time is maintained within the allowable range of measurement accuracy.

By adopting the above measurement steps, the measurement result can be realized without nonlinear error, and the measurement accuracy is not affected by the wire resistance and the constant current source accuracy, and the analysis is as follows:

Let all the wire resistances be equal, both are RL; the current values of the two constant current sources are equal in size under ideal conditions and equal to the design value, but the actual current values of the two constant current sources may not be exactly equal due to the actual accuracy. And deviation from the design value, set to II and 12 respectively. It is easy to conclude that after the first charge is completed, the voltage Vfl stored on the flying capacitor Cf is: W + /A ( 1 ) Similarly, after the second charging is completed, the voltage Vf2 stored on the flying capacitor Cf is:

ν / ₂ = / ₂ (^ + ^)-/Α ( 2 ) The average value of the voltage values stored twice on the flying capacitor Cf can be expressed as:

Vf = ^(Vf ₁ +Vf ₂ ) = ^(I ₁ + I ₂ )R _t ... It can be seen that the voltage value is independent of the wire resistance, that is, the influence of the wire resistance on the measurement result is eliminated; and the voltage is proportional to the thermal resistance signal, so the measurement method of the invention has no nonlinear error. The voltage value on the flying capacitor Cf is converted to a digital signal by the A/D converter and sent to the controller. Therefore, the digital signal of the final measurement result obtained by the controller can be expressed as: Code = 2' - = 2' ^ ~~

(4) where i is the number of bits of the A/D converter and Vref is the reference voltage of the A/D converter. As mentioned above, in practice, ^ and 12 will deviate from the design value. If the A/D converter uses a fixed reference voltage as the reference voltage Vref, the deviation of II and 12 will directly affect the accuracy of the final measurement result. In order to eliminate the influence of the deviation on the final measurement result, in the two A/D conversion process, the A/D converter adopts the voltage generated by combining II and 12 through the precision resistor Rref as the reference voltage Vref, at this time (4) Can be expressed as

2V _ref 2(I _{1 +} I ₂ )R _ref 2R _{ref ( 5 ) It} can be seen that the final measurement result is independent of the actual size of II and 12, thus eliminating the influence of the accuracy of the constant current source on the measurement result.

When there is common mode interference at both ends of the RTD, interference voltages of the same magnitude and direction are superimposed on both ends of the RTD. According to the above measurement process of the present invention, during the first and second charging of Cf, both ends of the thermal resistor Rt are respectively connected to both ends of the flying capacitor Cf, so the interference voltage signal is not stored in the flying capacitor. Cf. Therefore, the present invention is highly resistant to common mode interference. The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separate, and the components displayed as units may or may not be physical units, ie may be located A place, or it can be distributed to multiple network units. Some or all of the modules may be selected according to actual needs to achieve the objectives of the solution of the embodiment. of. Those of ordinary skill in the art can understand and implement without any creative effort. A person skilled in the art can understand that all or part of the process of implementing the above embodiment method can be completed by a computer program to instruct related hardware, and the program can be stored in a computer readable storage medium. When executed, the flow of an embodiment of the methods as described above may be included. The storage medium may be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM).

The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the embodiments of the invention. . Therefore, the present embodiments of the invention are not to be limited to the embodiments shown herein, but are to be accorded to the broadest scope of the principles and novel features disclosed herein.

Claims

Rights request

A measuring system for a thermal resistance signal, the system comprising: a first constant current source and a second constant current source, a flying capacitor, an analog to digital converter, a precision resistor, a controller, and a setting a charging control unit between the flying capacitor and the thermal resistor and connecting the first constant current source and the second constant current source, and a connection control unit disposed between the analog/digital converter and the flying capacitor;

The connection control unit is configured to connect the analog/digital converter and the first and second plates of the flying capacitor after the first charging and the second charging are respectively ended, The analog/digital converter converts the voltage signal stored between the flying capacitor plates into a first digital signal and a second digital signal; the first end of the precision resistor is grounded, and the second end is connected to the analog/digital converter And the second end of the precision resistor is connected to the first constant current source and the second constant current source by the charging control unit, wherein the charging control unit is further configured to control the first constant current source and The current outputted by the second constant current source is combined to flow through the precision resistor to provide a reference voltage for the analog/digital converter;

2. The measuring system of the thermal resistance signal according to claim 1, wherein the charging control unit comprises:

a third switch disposed between the first constant current source and the second plate of the flying capacitor, and a fourth switch disposed between the second constant current source and the first plate of the flying capacitor; When the three switches and the fourth switch are closed, the first constant current source and the second constant current source perform a second charging on the flying capacitor; And a fifth switch connected between the first constant current source and the second constant current source, connected to the first constant current source, and a sixth switch connected to the second constant current source; When the five switches and the sixth switch are closed, the currents output by the first constant current source and the second constant current source are combined to flow through the precision resistor to provide a reference voltage for the analog/digital converter.

3. The system of measuring a thermal resistance signal according to claim 2, wherein the system further comprises:

4. The system of measuring a thermal resistance signal according to claim 2, wherein the system further comprises:

The measuring system of the thermal resistance signal according to claim 1, wherein the connection control unit comprises: a first electrode disposed between the first plate of the flying capacitor and the analog/digital converter And a twelve switch, and a thirteenth switch disposed between the second plate of the flying capacitor and the analog/digital converter.

The system of measuring a thermal resistance signal according to claim 5, wherein the system further comprises:

a unity gain amplifier, a forward input of the unity gain amplifier is coupled to the twelfth switch, a negative input of the unity gain amplifier is coupled to an output, and the output is coupled to the analog to digital converter.

7. The thermal resistance signal measuring system according to claim 6, wherein the unity gain amplifier is an operational amplifier for causing the analog/digital converter to perform a voltage signal stored on the flying capacitor. During the transition time, the leakage current on the flying capacitor is maintained within the range required for measurement accuracy.

8. The thermal resistance signal measuring system according to claim 1, wherein said first The current values of one constant current source and the second constant current source are equal.

A measuring system for a thermal resistance signal according to any one of claims 2-8, wherein the switch is an analog switch.