CN205538016U - Three wire system pt100 platinum resistance temperature detection circuit - Google Patents

Abstract

The utility model relates to a temperature measurement technical field discloses a three wire system pt100 platinum resistance temperature detection circuit, include: pt100 platinum resistor sensor, constant current source, operational amplifier, first resistance, second resistance, third resistance, fourth resistance and the 5th resistance, the output of constant current source is connected pt100 platinum resistor sensor 's first end, first resistance, second resistance and the 3rd series resistance, the back one end of establishing ties is connected pt100 platinum resistor sensor 's second end is connected to constant current source, the other end, and ground connection, operational amplifier's positive input terminal connects between second resistance and the third resistance, the negative input end passes through the fourth ohmic connection pt100 platinum resistor sensor 's second end is connected between operational amplifier's negative input end and the output the 5th resistance. The utility model discloses a component that three wire system pt100 platinum resistance temperature detection circuit used is few, simple structure, low power dissipation, precision are high, can compensate the wire resistance that pt100 platinum resistance temperature measured in the gamut.

Description

Three-wire system Pt100 Pt Resistance Temperature Measuring Circuit

Technical field

The utility model relates to technical field of temperature measurement, particularly to a kind of three-wire system Pt100 Pt Resistance Temperature Measuring Circuit.

Background technology

Pt100 platinum thermal resistance sensor is that a kind of resistance value varies with temperature and the temperature sensor that changes, has stable Good, the precision advantages of higher of property, is temperature sensor the most frequently used in industrial processes.Temperature measuring circuit is mainly by sensing Device, measuring circuit and connection wire composition, connect wire and generally use three-wire system connection.In order to eliminate the resistance value connecting wire Impact on measured value, will compensate it in measuring circuit.In existing measuring circuit, some simple circuit can only Certain measurement point in the range of gamut is compensated, and other compensation precision measuring point is poor.And can be at gamut model The circuit carrying out high-accuracy compensation in enclosing is the most complicated, and power consumption is high.

Utility model content

The utility model proposes a kind of three-wire system Pt100 Pt Resistance Temperature Measuring Circuit, solving can be in full dose in prior art High-precision compensation circuit structure is carried out complicated, the problem that power consumption is high in the range of journey.

Three-wire system Pt100 Pt Resistance Temperature Measuring Circuit of the present utility model, including: Pt100 platinum sensor, constant-current source, Operational amplifier, the first resistance, the second resistance, the 3rd resistance, the 4th resistance and the 5th resistance；The output of described constant-current source is even Connecing the first end of described Pt100 platinum sensor, the first resistance, the second resistance and the 3rd resistant series, after series connection, one end is even Connecing described constant-current source, the other end connects the second end of Pt100 platinum sensor, and ground connection, described operational amplifier the most defeated Entering end to be connected between described second resistance and the 3rd resistance, negative input end connects described Pt100 RTD by the 4th resistance Second end of sensor, connects described 5th resistance between negative input end and the output of described operational amplifier.

Three-wire system Pt100 Pt Resistance Temperature Measuring Circuit of the present utility model use element is few, simple in construction, low in energy consumption, smart Degree height, can compensate conductor resistance in Pt100 platinum resistance temperature is measured gamut.

Accompanying drawing explanation

In order to be illustrated more clearly that the utility model embodiment or technical scheme of the prior art, below will be to embodiment Or the required accompanying drawing used is briefly described in description of the prior art, it should be apparent that, the accompanying drawing in describing below is only It is embodiments more of the present utility model, for those of ordinary skill in the art, before not paying creative work Put, it is also possible to obtain other accompanying drawing according to these accompanying drawings.

Fig. 1 is a kind of three-wire system Pt100 Pt Resistance Temperature Measuring Circuit structural representation of the present utility model.

Detailed description of the invention

Below in conjunction with the accompanying drawing in the utility model embodiment, the technical scheme in the utility model embodiment is carried out Clearly and completely describe, it is clear that described embodiment is only a part of embodiment of the utility model rather than whole Embodiment.Based on the embodiment in the utility model, those of ordinary skill in the art are not under making creative work premise The every other embodiment obtained, broadly falls into the scope of the utility model protection.

As it is shown in figure 1, the three-wire system Pt100 Pt Resistance Temperature Measuring Circuit of the present embodiment, including: Pt100 platinum sensor (shown in dotted line frame, Rt is Pt100 RTD, and r1, r2 and r3 are the conductor resistances of three-wire system connection), constant-current source A, operation amplifier Device U1, the first resistance R1, the second resistance R2, the 3rd resistance R3, the 4th resistance R4 and the 5th resistance R5.The output of constant-current source A Connect the first end of Pt100 platinum sensor, the first resistance R1, the second resistance R2 and the 3rd resistance R3 series connection, after series connection one End connects constant-current source A, and the other end connects the second end of Pt100 platinum sensor, and ground connection.The positive input of operational amplifier U1 End is connected between the second resistance R2 and the 3rd resistance R3, and negative input end connects described Pt100 RTD by the 4th resistance R4 Second end of sensor.The 5th resistance R5 is connected between negative input end and the output of operational amplifier U1.

Three-wire system connection uses three same wires to connect Pt100 RTD, it is generally recognized that r1=r2=r3=r.a、 B, c are three binding posts that sensor connects wire, the voltage V between a, c_acInclude voltage V on RTD_RtLead with 2 Voltage 2V on line resistance_r, voltage V between b, c_bcIt is voltage V on a conductor resistance_r, it is added to fortune by resistor network respectively Calculate the positive-negative input end of amplifier, by the characteristic of operational amplifier, obtain only powering on RTD at operational amplifier output terminal Pressure V_RtProportional, and with voltage V on conductor resistance_rUnrelated voltage output.So, conductor resistance is just eliminated to measured temperature Impact.Concrete calculating process is as follows:

V_a、V_bIt is the voltage on a, b terminal respectively, c end ground connection.I is the output electric current of constant-current source A.R1、R2、R3、R4、R5 For precision resistance, making R1, R2, R3, R4 and R5 meet R3=R1, R5=2nR1, R4=nR2, wherein, n is normal number.U1 is micro- Power consumption cmos operational amplifier, V₊It is positive input terminal, V_-It is negative input end, V_oIt it is output.In circuit, R1 >=20k is chosen Ω, so can be far longer than the resistance of r1+Rt+r2 with the resistance of R1+R3+R5, is approximately considered and flows through the electric current of r1, Rt, r2 and be I, simultaneously it is also contemplated that V_b=V_r。

V_a=I (r1+Rt+r2)=I (Rt+2 r) (1)

V_b=I r1=I r (2)

$V_{+}=\frac{R3}{R1+R2+R3}\·V_a=\frac{R1}{2\·R1+R2}{V}_a---\left(3\right)$

$V_{-}=\frac{R5}{R4+R5}\·V_b+\frac{R4}{R4+R5}\·V_o=\frac{2\·n\·R1}{n\·R2+2\·n\·R1}{V}_b+\frac{n\·R2}{n\·R2+2\·n\·R1}{V}_o---\left(4\right)$

Characteristic V according to operational amplifier₊=V_-, formula (1) and (2) are brought into respectively (3) and (4) and can get:

$V_o=\frac{R1}{R2}\·I\·Rt---\left(5\right)$

In this circuit, R1, R2, I are definite value, therefore output voltage V_oThe most only follow resistance R of Pt100 platinum resistance thermometer sensor,_tBecome Change, and unrelated with resistance r1, r2 and the r3 connecting wire, thus reach the purpose that sensor is accurately compensated.And from Circuit diagram can be seen that the three-wire system Pt100 Pt Resistance Temperature Measuring Circuit element of the present embodiment is few, simple in construction, low in energy consumption.

The foregoing is only preferred embodiment of the present utility model, not in order to limit the utility model, all at this Within the spirit of utility model and principle, any modification, equivalent substitution and improvement etc. made, should be included in the utility model Protection domain within.

Claims (1)

1. a three-wire system Pt100 Pt Resistance Temperature Measuring Circuit, it is characterised in that including: Pt100 platinum sensor, constant-current source, Operational amplifier, the first resistance, the second resistance, the 3rd resistance, the 4th resistance and the 5th resistance；The output of described constant-current source is even Connecing the first end of described Pt100 platinum sensor, the first resistance, the second resistance and the 3rd resistant series, after series connection, one end is even Connecing described constant-current source, the other end connects the second end of Pt100 platinum sensor, and ground connection, described operational amplifier the most defeated Entering end to be connected between described second resistance and the 3rd resistance, negative input end connects described Pt100 RTD by the 4th resistance Second end of sensor, connects described 5th resistance between negative input end and the output of described operational amplifier.