CN203479906U - Four-wire system Pt100 resistor measuring circuit - Google Patents

Four-wire system Pt100 resistor measuring circuit Download PDF

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Publication number
CN203479906U
CN203479906U CN201320533046.0U CN201320533046U CN203479906U CN 203479906 U CN203479906 U CN 203479906U CN 201320533046 U CN201320533046 U CN 201320533046U CN 203479906 U CN203479906 U CN 203479906U
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resistance
wire
resistor
measuring
precision
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CN201320533046.0U
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王昆鹏
田佳林
刘立波
张月清
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CHANGCHUN METEOROLOGICAL INSTRUMENT RESEARCH INSTITUTE CO LTD
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CHANGCHUN METEOROLOGICAL INSTRUMENT RESEARCH INSTITUTE CO LTD
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Abstract

The utility model relates to a four-wire system Pt100 resistor measuring circuit for the purpose of improving Pt100 resistor measuring precision and reducing the size and weight of utilized components. The four-wire system Pt100 resistor measuring circuit comprises a 24-digit AD conversion chip AD7793 which is provided with a constant current source generation circuit and a three-path simulation signal acquisition interface. The 24-digit AD conversion chip AD7793 can measure the differential voltage of a detected resistor Py100 and a standard resistor under the control of a CPU. Since only one 24-digit AD conversion chip AD7793 and one standard resistor are utilized for realizing four-wire system high-precision Pt100 resistor measuring, the four-wire system Pt100 resistor measuring circuit has the advantages of miniaturization and high precision.

Description

A kind of four-wire system Pt100 resistance measuring circuit
Technical field
The utility model relates to a kind of metering circuit, and particularly a kind of based on AD7793 and a precision resistance, miniaturization is high-precision, four-wire system Pt100 resistance measuring circuit.
Background technology
At present, the circuit of measuring platinum resistance Pt100 has two-wire system, three-wire system and four-wire system, and wherein the resistance of two-wire system and three-wire system measurement platinum resistance is subject to the impact of connecting line length.Four-wire system can be removed the impact of connecting line length.The general constant current driving platinum resistance that adopts during measurement, drive current is approximately 1mA left and right.This just requires the raw circuit of persevering miscarriage.The electric current that general constant-current circuit produces is subject to the impact of temperature, and AD chip is when measure, and the precision of measurement is temperature influence also.The resistance temperature influence of Pt100,1 ℃ of every variation, resistance value approximately changes 0.394 Ω, 0.1 ℃ of every variation, resistance value approximately changes 0.0394 Ω, namely 39m Ω.General temperature measurement circuit will reach the precision of 0.1 ℃, needs doing mathematics correction.
Summary of the invention
The utility model is in order to improve the precision of measuring Pt100 resistance, and reduces the volume and weight of components and parts used, provides a kind of based on AD7793 and a precision resistance, miniaturization, high-precision, four-wire system Pt100 resistance measuring circuit.
To achieve these goals, the technical solution of the utility model is specific as follows:
A four-wire system Pt100 resistance measuring circuit, comprising: 24 AD conversion chip AD7793;
24 described AD conversion chip AD7793 are with constant current source generating circuit, and with 3 road collection of simulant signal interfaces;
24 described AD conversion chip AD7793 can measure the dividing potential drop of measured resistance Pt100 and measuring resistance under the control of CPU.
In technique scheme, described measuring resistance is that 100 Ω High Precision Low Temperatures float resistance.
The beneficial effects of the utility model are:
The four-wire system Pt100 resistance measuring circuit that the utility model provides is only to utilize 24 AD chip AD7793 of a slice and measuring resistance to realize the high precision Pt100 resistance measurement of four-wire system, and this metering circuit has miniaturization and high-precision feature.Wherein, 24 AD chip AD7793, resolution is enough, and with constant current source generating circuit, and self is with 3 road collection of simulant signal interfaces, enough realizes the measurement of high-precision Pt100 resistance.
When measuring resistance be High Precision Low Temperature float 100 Ω resistance time, make resistance measure resistance error between 80 Ω and 120 Ω in 20m Ω, measuring error is 0.05%.
CPU controls AD7793 and gathers the measured resistance Pt100 of 2 passages and the voltage of measuring resistance, identical owing to flowing through the electric current of measured resistance Pt100 and measuring resistance, and the resistance of measuring resistance is fixed value, therefore the resistance of Pt100 resistance only depends on the ratio of the two voltage, eliminated the impact of continuous current, measuring accuracy improves.
Accompanying drawing explanation
Below in conjunction with the drawings and specific embodiments, the utility model is described in further detail.
Fig. 1 is the hardware elementary diagram of a kind of four-wire system Pt100 resistance measuring circuit of the utility model.
Fig. 2 is the software principle figure of a kind of four-wire system Pt100 resistance measuring circuit of the utility model.
Embodiment
Below in conjunction with accompanying drawing, the utility model is described in detail.
By reference to the accompanying drawings 1 and accompanying drawing 2 explanation the present embodiment.Measured resistance Pt100 and 100 Ω High Precision Low Temperatures are floated to resistance and be cascaded, utilize the 1mA continuous current that AD7793 produces to drive.As shown in Figure 1, the resistance of Pt100 resistance is R t, its voltage is V t; The resistance that 100 Ω High Precision Low Temperatures float resistance is R 1, its voltage is V 1.If the electric current that constant current source produces is I 1, with passage one and the passage two of AD7793, measure V respectively tand V 1.Open the amplifier of AD7793 inside, the passage one of AD7793 and passage two are high-impedance state like this, do not have electric current to pass through on lead-in wire, and the length of lead-in wire can be ignored, and so just do not introduce lead resistance.When variation of ambient temperature, the electric current I that AD7793 produces 1changing, is not 1mA constant current, but I 2, but flow through resistance R tand R 1electric current identical, and due to R 1for the resistance that High Precision Low Temperature floats, resistance value is still 100 Ω.
At this moment R tvoltage be V t2, R 1voltage be V 12.By I 2=V t2/ R t, I 2=V 12/ R 1, can draw V t2/ R t=V 12/ R 1, R namely t=(V t2* R 1)/V 12.At R t=(V t2* R 1)/V 12in this equation, cancellation the impact of constant current source, R 1for constant, the resistance of Pt100 resistance only depends on V t2/ V 12ratio, measuring accuracy improves.
Obviously, above-described embodiment is only for example is clearly described, and the not restriction to embodiment.For those of ordinary skill in the field, can also make other changes in different forms on the basis of the above description.Here exhaustive without also giving all embodiments.And among the protection domain that the apparent variation of being extended out thus or change are still created in the utility model.

Claims (2)

1. a four-wire system Pt100 resistance measuring circuit, is characterized in that, comprising: 24 AD conversion chip AD7793;
24 described AD conversion chip AD7793 are with constant current source generating circuit, and with 3 road collection of simulant signal interfaces;
24 described AD conversion chip AD7793 can measure the dividing potential drop of measured resistance Pt100 and measuring resistance under the control of CPU.
2. four-wire system Pt100 resistance measuring circuit according to claim 1, is characterized in that, described measuring resistance is that 100 Ω High Precision Low Temperatures float resistance.
CN201320533046.0U 2013-08-29 2013-08-29 Four-wire system Pt100 resistor measuring circuit Active CN203479906U (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201320533046.0U CN203479906U (en) 2013-08-29 2013-08-29 Four-wire system Pt100 resistor measuring circuit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201320533046.0U CN203479906U (en) 2013-08-29 2013-08-29 Four-wire system Pt100 resistor measuring circuit

Publications (1)

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CN203479906U true CN203479906U (en) 2014-03-12

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104614589A (en) * 2015-01-19 2015-05-13 浙江中控自动化仪表有限公司 Lead-resistance-removed resistance signal source and resistance measuring circuit thereof
CN109358236A (en) * 2018-10-16 2019-02-19 Oppo广东移动通信有限公司 For measuring the circuit and method of resistance

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104614589A (en) * 2015-01-19 2015-05-13 浙江中控自动化仪表有限公司 Lead-resistance-removed resistance signal source and resistance measuring circuit thereof
CN104614589B (en) * 2015-01-19 2017-07-28 浙江中控自动化仪表有限公司 Resistance signal source and its resistance measuring circuit that a kind of lead resistance is eliminated
CN109358236A (en) * 2018-10-16 2019-02-19 Oppo广东移动通信有限公司 For measuring the circuit and method of resistance

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