CN202002607U

CN202002607U - Differential transformer type displacement sensor with adjustable temperature drift coefficient

Info

Publication number: CN202002607U
Application number: CN2011200926914U
Authority: CN
Inventors: 李为
Original assignee: HEFEI GAOCHUANG SENSOR CO Ltd
Current assignee: HEFEI GAOCHUANG SENSOR CO Ltd
Priority date: 2011-04-01
Filing date: 2011-04-01
Publication date: 2011-10-05
Anticipated expiration: 2021-04-01

Abstract

The utility model relates to a differential transformer type displacement sensor with adjustable temperature drift coefficient, which comprises a LVDT (linear variable differential transformer). A primary coil of the LVDT is connected with an output end of a voltage/current hybrid exciting circuit, the primary coil of the LVDT and the voltage/current hybrid exciting circuit form a loop, an input end of the voltage/current hybrid exciting circuit is connected with an output end of an oscillator, a secondary coil of the LVDT is connected with an input end of a demodulation amplifier circuit. The voltage/current hybrid exciting circuit can generate temperature drift, the temperature drift direction is opposite to the temperature drift direction of eta according to the principle of impedance loop, the temperature drift of the voltage/current hybrid exciting circuit and the temperature drift of the eta are equal in magnitude and opposite in direction by changing voltage/current hybrid ratio, and thereby the problem of temperature drift of the differential transformer can be well solved. The differential transformer type displacement sensor is low in cost, and precision of the displacement sensor is improved greatly.

Description

A kind of temperature is floated the adjustable differential transformer displace of coefficient

Technical field

The utility model relates to a kind of displacement transducer, and especially a kind of temperature is floated the adjustable differential transformer displace of coefficient.

Background technology

The history of the application of differential transformer displace existing decades, it has, and antijamming capability is strong, long service life, can adapt to characteristics such as various rugged surroundings and be widely used.Yet, differential transformer (LVDT) has certain temperature drift, this drift fails to be well solved for a long time always, this directly has influence on the precision of differential transformer displace, can only make this sensor application in the place of low precision, the theory diagram of traditional differential transformer displace is as shown in Figure 1.

Signal of sensor is to be subtracted each other by the voltage on twice level coils to form as seen from Figure 1.When iron core during in the centre position, the temperature on twice level coils is floated and is subtracted each other and offset; When iron core departed from the centre position, the temperature of twice level coils was floated small one and large one, and they subtract each other can't offset and produce temperature and float.The side-play amount that this temperature is floated along with iron core increases and increases, and temperature is floated curve as shown in Figure 2, and wherein abscissa axis S is displacement, and axis of ordinates V is an output signal.The temperature of differential transformer (LVDT) is floated very complicated, and this just fails to obtain the reason of fine solution for a long time always.

The utility model content

The purpose of this utility model be to provide a kind of cost low, can at utmost reduce the temperature that temperature is floated, precision is high and float the adjustable differential transformer displace of coefficient.

For achieving the above object, the utility model has adopted following technical scheme: a kind of temperature is floated the adjustable differential transformer displace of coefficient, comprise differential transformer LVDT, the primary coil of described differential transformer LVDT links to each other with the output terminal of voltage/current mixed excitation circuit, the primary coil of differential transformer LVDT and voltage/current mixed excitation circuit constitute the loop, the input end of voltage/current mixed excitation circuit links to each other with the output terminal of oscillator, and the secondary coil of differential transformer LVDT links to each other with the input end of demodulation amplifying circuit.

As shown from the above technical solution, the utility model is compared with traditional differential transformer displace, make the constant voltage exciting circuit into voltage/current mixed excitation circuit, this voltage/current mixed excitation circuit can produce temperature and float, according to the impedance circuit theory, its temperature is floated direction and the temperature of η, and to float direction opposite, its temperature floated with the temperature of η float opposite sign but equal magnitude, float problem with regard to the temperature that can solve differential transformer like this by changing the voltage/current mixing ratio.Cost of the present utility model is low, has improved the precision of displacement transducer greatly.

Description of drawings

Fig. 1 is the circuit block diagram of traditional differential transformer displace;

Fig. 2 is that the temperature of differential transformer LVDT is floated curve;

Fig. 3,4 is circuit block diagram of the present utility model.

Embodiment

A kind of temperature is floated the adjustable differential transformer displace of coefficient, comprise differential transformer LVDT, the primary coil of described differential transformer LVDT links to each other with the output terminal of voltage/current mixed excitation circuit 2, the primary coil of differential transformer LVDT and voltage/current mixed excitation circuit 2 constitute the loop, the input end of voltage/current mixed excitation circuit 2 links to each other with the output terminal of oscillator 1, the secondary coil of differential transformer LVDT links to each other with the input end of demodulation amplifying circuit 3, as shown in Figure 3.

Because all material of formation differential transformer LVDT nearly all can produce temperature and float, only their amount of influence varies, and below the bigger differential transformer LVDT material of the amount of influence is made introduction.

The first, inner and outer pipes: inner and outer pipes can produce current vortex, and this current vortex is loss to differential transformer LVDT, and the size of loss is relevant with the resistivity of inner and outer pipes, and resistivity can be subjected to Temperature Influence.Therefore, inner and outer pipes can produce temperature and float, and the character that its temperature is floated is that positive temperature is floated, and when promptly the temperature of inner and outer pipes raise, the output of displacement transducer was also along with rising;

The second, coil: the resistance of coil and volume can increase along with the rising of temperature, and this can cause the variation of primary and secondary mutual induction amount and produce temperature and floats.The character that the coil temperature is floated is that subzero temperature floats, and when promptly the temperature of coil raise, the output of sensor was along with reduction.

The 3rd, iron core: iron core be magnetic conductor be again the eddy current body, when the iron core temperature raise, magnetoconductivity can descend, its influence is far longer than the influence of eddy current.The character that the iron core temperature is floated is that subzero temperature floats, and the individual difference of iron core is bigger, and their temperature is floated difference can reach tens times sometimes, and this is relevant with factors such as their material composition, impure what, thermal treatment, frequency of operation.

As seen from the above analysis, the temperature of differential transformer LVDT is floated very complicated, and this also is the warm always for a long time reason of failing to obtain fine solution of floating.

All transformer primary and secondary voltage relationships can be expressed by formula (1):

Vc?=?ηVo （1）

Vc is a secondary voltage in the formula (1), and Vo is a primary voltage, and η is a coefficient, it with the transformation ratio of the magnetoconductivity of the eddy current loss of transformer, iron core, coil, to shake factor such as frequency relevant.If Vo is stable constant pressure source, output voltage V c will fluctuate along with the fluctuation of η so.

As shown in Figure 4, described voltage/current mixed excitation circuit 2 comprises penultimate amplifier IC, the end of the in-phase input end connecting resistance R1 of penultimate amplifier IC, the other end ground connection of resistance R 1, the inverting input of penultimate amplifier IC connects the output terminal of oscillator 1, the primary coil of the output termination differential transformer LVDT of penultimate amplifier IC, resistance R 2 is connected across the inverting input of penultimate amplifier IC, on the output terminal, the inverting input of one termination penultimate amplifier IC of resistance R 3, the other end of resistance R 3 respectively with resistance R 4, the primary coil of differential transformer LVDT links to each other, the other end ground connection of resistance R 4.The secondary coil of described differential transformer LVDT is made up of first and second secondary coil, and first and second secondary coil links to each other with the input end of demodulation amplifying circuit 3 respectively.

As shown in Figure 4, it is oscillator signal about 2K that oscillator 1 provides a frequency to voltage/current mixed excitation circuit 2, and resistance R 1, R2, R3, R4, penultimate amplifier IC constitute voltage/current mixed excitation circuit 2.In this circuit, when resistance R 3 is infinity, the voltage/current mixed excitation has just become the constant voltage excitation, so-called constant voltage excitation is meant that the primary voltage Vo of transformer is constant, at this moment, floats if produce temperature, η changes, then according to formula (1) as can be known, the secondary voltage Vc of transformer also changes thereupon, causes the accuracy of detection step-down of sensor; When resistance R 3 was zero, the voltage/current mixed excitation had just become constant current drive, and the resistance that therefore changes resistance R 3 just can change voltage/current mixed excitation ratio.

As shown in Figure 4,2 pairs of oscillator signals of voltage/current mixed excitation circuit amplify, and produce the voltage/current mixed excitation signal of an about 5V, and the elementary of differential transformer LVDT encouraged.When the generation temperature was floated, if η diminishes, then the primary consumer of differential transformer LVDT became big, and primary voltage Vo becomes greatly, because the change direction of η and changing in the opposite direction of primary voltage Vo can farthest be offset temperature and be floated the influence that is produced; Otherwise also set up.Sensor parameters at different ranges carries out the temperature compensation debugging, determines the resistance of resistance R 3, and resistance R 3 is used to regulate temperature and floats sensitivity, and resistance R 4 is used to cooperate resistance R 3 adjusting temperature to float sensitivity, so just can play good temperature compensation function.When the iron core of differential transformer LVDT produced displacement, two secondary coils just produced differential wave V1 and V2, by simulating signal Vc that automatic control system can be discerned of demodulation amplifying circuit 3 outputs.

The utility model is compared with traditional circuit, and constant voltage excitation has been made into voltage/current mixed excitation circuit 2, and this mixed excitation circuit can produce temperature and float, and according to the impedance circuit theory, its temperature is floated direction and the temperature of η, and to float direction opposite.By changing the voltage/current mixing ratio, just change the size of resistance R 3 resistances, its temperature is floated with the temperature of η float opposite sign but equal magnitude, float problem with regard to the temperature that can solve differential transformer like this.

Claims

1. a temperature is floated the adjustable differential transformer displace of coefficient, comprise differential transformer LVDT, it is characterized in that: the primary coil of described differential transformer LVDT links to each other with the output terminal of voltage/current mixed excitation circuit (2), the primary coil of differential transformer LVDT and voltage/current mixed excitation circuit (2) constitute the loop, the input end of voltage/current mixed excitation circuit (2) links to each other with the output terminal of oscillator (1), and the secondary coil of differential transformer LVDT links to each other with the input end of demodulation amplifying circuit (3).

2. temperature according to claim 1 is floated the adjustable differential transformer displace of coefficient, it is characterized in that: described voltage/current mixed excitation circuit (2) comprises penultimate amplifier IC, the end of the in-phase input end connecting resistance R1 of penultimate amplifier IC, the other end ground connection of resistance R 1, the inverting input of penultimate amplifier IC connects the output terminal of oscillator (1), the primary coil of the output termination differential transformer LVDT of penultimate amplifier IC, resistance R 2 is connected across the inverting input of penultimate amplifier IC, on the output terminal, the inverting input of one termination penultimate amplifier IC of resistance R 3, the other end of resistance R 3 respectively with resistance R 4, the primary coil of differential transformer LVDT links to each other, the other end ground connection of resistance R 4.

3. temperature according to claim 1 is floated the adjustable differential transformer displace of coefficient, it is characterized in that: the secondary coil of described differential transformer LVDT is made up of first and second secondary coil, and first and second secondary coil links to each other with the input end of demodulation amplifying circuit (3) respectively.