CN210005595U

CN210005595U - thermal resistance four-wire system real-time measuring circuit

Info

Publication number: CN210005595U
Application number: CN201920401693.3U
Authority: CN
Inventors: 郑陆君
Original assignee: SHANGHAI WEICHENG ELECTRIC EQUIPMENT CORP
Current assignee: SHANGHAI WEICHENG ELECTRIC EQUIPMENT CORP
Priority date: 2019-03-27
Filing date: 2019-03-27
Publication date: 2020-01-31
Anticipated expiration: 2029-03-27

Abstract

The utility model discloses an kind of thermal resistance four-wire system real-time measurement circuit, including the constant current source, the constant current source is measured thermal resistance, resistance by the series connection in proper order, is measured the both ends of thermal resistance and preamplifier's positive negative pole parallel connection, preamplifier's output and analog-to-digital AD converter are connected, a serial communication port, end and preamplifier's the measured thermal resistance between the positive pole be connected through electronic switch, be connected through second electronic switch between end in addition of thermal resistance and preamplifier's the positive pole, be connected through third electronic switch between end in addition of thermal resistance and preamplifier's the negative pole, preamplifier's negative pole and fourth electronic switch are connected, the utility model discloses a measuring circuit realizes simply, reliably, not only is applicable to single channel thermal resistance four-wire system and measures, also is applicable to the measurement of multichannel thermal resistance four-wire system, and can real-time measurement constant current source value.

Description

thermal resistance four-wire system real-time measuring circuit

Technical Field

The utility model relates to an kind of thermal resistance four-wire system real-time measurement circuit belongs to the application of temperature intelligent measuring device in the industrial production process control.

Background

In the control of industrial production process, because times of elements of the thermal resistor have high measurement accuracy, stable performance and easy processing, the thermal resistor is applied to the application field of temperature measurement and control of industrial equipment by , the thermal resistor is a temperature sensing element for converting temperature change into resistance value change, resistance signals are generally required to be transmitted to a temperature measuring device through leads, and in order to ensure the temperature measurement accuracy, the thermal resistor is commonly measured by a four-wire system.

The resistance measurement is generally applied to because the constant current source measurement mode is a mode of generating voltage at two ends of a resistance by flowing constant current through the measured resistance and has strong anti-interference capability in industrial field signal measurement.

A four-wire measurement circuit of thermal resistance is shown in FIG. 1, and the circuit signal conversion process is as follows:

1. constant current source I_GFlows in from the A end and passes through a thermal resistor R_xFlows out to the B terminal and then flows through a resistor R_YBack to reference;

2. preamplifier U₁Heating resistor R_xThe voltages at the two ends are amplified and then are sent to an analog-to-digital A/D converter U₂Obtaining a measurement voltage V_ab；

3. According to formula V_ab＝R_x*I_GThus obtaining a thermal resistance R_xThe measured value of (2): r_x＝V_ab/I_G。

Preamplifier U in fig. 1₁And an analog-to-digital A/D converter U₂The device is a high-precision device with ultra-low temperature drift and time drift, and the influence on the measurement precision can be ignored. Thus, the thermal resistance R is affected_xThe main measurement precision is constant current source I_GThe accuracy of (2).

Because of the constant current source I_G, which vary slightly with temperature, require a constant current source I to obtain high measurement accuracy_GThe real-time measurement is carried out, thus an additional measurement channel circuit is required, and a measurement constant current source I is caused_GAnd measuring the thermal resistance R_xThe circuit of (2) is not loops, and there is a channel error in the measurement.

Disclosure of Invention

The to-be-solved technical problem of the utility model is: solves the problem of how to carry out constant current source I under the condition of not adding an additional measuring channel circuit_GThe problem of performing real-time measurements.

In order to solve the technical problem, the utility model provides an kinds of thermal resistance four-wire system real-time measurement circuit, including the constant current source, the constant current source is by survey thermal resistance, resistance by the series connection in proper order, by survey thermal resistance's both ends and preamplifier's positive negative pole parallel connection, preamplifier's output and analog-to-digital A/D converter are connected, its characterized in that, by being connected through electronic switch between by the end of thermal resistance and preamplifier's the positive pole, by being connected through the second electronic switch between end in addition of survey thermal resistance and preamplifier's the positive pole, by being connected through the third electronic switch between end in addition of survey thermal resistance and preamplifier's the negative pole, preamplifier's negative pole and fourth electronic switch are connected.

Preferably, the resistor is connected with a reference ground, and the negative pole of the preamplifier is connected with the reference ground through a fourth electronic switch.

Preferably, the resistor is a wire-wound resistor.

The utility model discloses a measuring circuit realizes simply, reliably, not only is applicable to the single channel thermal resistance four-wire system and measures, also is applicable to the measurement of multichannel thermal resistance four-wire system, and can real-time measurement constant current source value. The utility model discloses a measuring circuit production, debugging and maintenance are simple, convenient.

Drawings

FIG. 1 is a schematic diagram of a conventional four-wire measurement circuit for thermal resistors;

fig. 2 is a schematic diagram of a four-wire real-time measuring circuit for thermal resistors according to the present invention.

Detailed Description

In order to make the present invention more comprehensible, preferred embodiments are described in detail below with reference to the accompanying drawings.

The utility model discloses a kinds of thermal resistance four-wire system real-time measuring circuit, as shown in fig. 2, it is mainly by survey thermal resistance R_xFour electronic switches (i.e. th electronic switch K)₁A second electronic switch K₂And a third electronic switch K₃And a fourth electronic switch K₄) 320 omega high-precision wire-wound resistor (namely resistor R) and constant current source I_GPreamplifier U₁Analog-to-digital A/D converter U₂And (4) forming.

Constant current source I_GThe measured thermal resistors R are sequentially connected in series_xResistance R, measured thermal resistance R_xBoth ends of (1) and a preamplifier U₁Positive and negative electrodes of the pre-amplifier U are connected in parallel₁And an analog-to-digital A/D converter U₂Characterized by that, the measured thermal resistance R_x terminal and preamplifier U₁Through an th electronic switch K₁Connecting, measured thermal resistance R_xAnother terminal and a preamplifier U₁Between the positive poles of the two electrodes through a second electronic switch K₂Connecting, measured thermal resistance R_xAnother terminal and a preamplifier U₁Between the negative poles of the three-phase alternating current transformer through a third electronic switch K₃Connecting, pre-amplifier U₁Negative pole and fourth electronic switch K₄And (4) connecting. The resistor R is connected with a reference ground, and the preamplifier U₁Is connected with the reference ground through a fourth electronic switch K₄And (4) connecting.

The utility model discloses a theory of operation does:

1. th electronic switch K₁And a third electronic switch K₃Open, second electronic switch K₂And a fourth electronic switch K₄And (5) closing. Constant current source I_GFlows in from the A end and passes through a measured thermal resistance R_xThe current flows out to the end B and then flows through a wire-wound resistor of 320 omega to return to the reference ground;

2. preamplifier U₁The voltage on the 320 omega wire-wound resistor is amplified and then is sent to an analog-to-digital A/D converter U₂Obtaining a measurement voltage V_G；

3. According to formula V_G＝320*I_GThus obtaining a constant current source I_GThe measured value of (2): i is_G＝V_G/320。

4. Second electronic switch K₂And a fourth electronic switch K₄Open, th electronic switch K₁And a third electronic switch K₃And (5) closing. Constant current source I_GFlows in from the A end and passes through a measured thermal resistance R_xThe current flows out to the end B and then flows through a wire-wound resistor of 320 omega to return to the reference ground;

5. front sideAmplifier U₁To-be-measured thermal resistance R_xThe voltages at the two ends are amplified and then are sent to an analog-to-digital A/D converter U₂Obtaining a measured voltage V_ab；

6. According to V_ab＝R_x*I_GAnd I_G＝V_G/320, obtaining the measured thermal resistance R_xThe measured value of (2):

R_x＝320*V_ab/V_G。

from the formula R_x＝320*V_ab/V_GIt can be known that the measured thermal resistance R_xMeasured value and constant current source I_GThe precision has no correlation. Like this, use the utility model discloses a high accuracy requirement of industry thermal resistance real-time measurement can be realized to the circuit. And, measure the constant current source I_GAnd a thermal resistor R_xThe measuring loops are all constant current sources I_GThe same loop is passed through, so there is no channel error in the measurement.

Claims

The four-wire real-time measuring circuit for the thermal resistor comprises a constant current source and a tested thermal resistor and a resistor which are sequentially connected in series, wherein two ends of the tested thermal resistor are connected with the positive electrode and the negative electrode of a preamplifier in parallel, the output end of the preamplifier is connected with an analog-to-digital A/D converter, and the four-wire real-time measuring circuit is characterized in that the end of the tested thermal resistor is connected with the positive electrode of the preamplifier through a electronic switch, the other end of the tested thermal resistor is connected with the positive electrode of the preamplifier through a second electronic switch, the other end of the tested thermal resistor is connected with the negative electrode of the preamplifier through a third electronic switch, and the negative electrode of the preamplifier is connected with a fourth electronic switch.
2. The type of thermal resistor four-wire real-time measuring circuit as claimed in claim 1, wherein the resistor is connected to a reference ground, and the negative pole of the preamplifier is connected to the reference ground through a fourth electronic switch.
3. The type of thermal resistor four-wire real-time measuring circuit as claimed in claim 1, wherein the resistor is a wire wound resistor.