CN114112092A

CN114112092A - Sensor ambient temperature measuring circuit and sensor

Info

Publication number: CN114112092A
Application number: CN202111419087.2A
Authority: CN
Inventors: 李明夏; 曹龙轩; 赵国锋; 李伟
Original assignee: Anhui Jianxing Technology Co ltd
Current assignee: Anhui Jianxing Technology Co ltd
Priority date: 2021-11-26
Filing date: 2021-11-26
Publication date: 2022-03-01

Abstract

The invention discloses a sensor environment temperature measuring circuit and a sensor, and belongs to the technical field of sensors. Aiming at the problems of poor precision and complex system in the prior art, the invention provides a sensor environment temperature measuring circuit and a sensor, which comprise a loop formed by a probe and an excitation source, a direct current bias circuit and a divider resistor, wherein the direct current bias circuit and the divider resistor are superposed or externally added on the loop formed by the probe and the excitation source; and the compensation loop comprises a low-pass filter circuit, an amplifying circuit, a compensation circuit and a demodulation circuit which are sequentially arranged to form a compensation loop, and is arranged between the probe and the voltage dividing resistor to perform voltage compensation. The circuit and the sensor have high integration degree and compact structure, can accurately reflect the temperature at a measuring point, and have better compensation effect.

Description

Sensor ambient temperature measuring circuit and sensor

Technical Field

The invention relates to the technical field of sensors, in particular to a sensor environment temperature measuring circuit and a sensor.

Background

The inductive sensor is a widely used sensor, can be used for measuring vibration, displacement, thickness, angle and the like, and can be divided into a self-inductive sensor, a differential variable-voltage sensor and an eddy current sensor according to different probe structures of the sensor. The self-inductance sensor uses one coil as a probe designed such that the inductance changes with changes in other physical quantities, and detects changes in other physical quantities by detecting changes in the inductance of the coil using a high-frequency alternating current excitation coil. The differential transformer type sensor uses an exciting coil and two secondary coils which are connected in series in an opposite direction as a probe, and when the distance between the exciting coil and the two secondary coils changes, the voltages sensed by the two secondary coils change, so that the displacement change is reflected. The eddy current sensor uses a coil as a probe, uses high-frequency alternating current to excite the coil to generate a high-frequency magnetic field, the high-frequency magnetic field excites eddy current in a target metal plate, and the eddy current has two effects, on one hand, a magnetic field opposite to the excitation magnetic field is generated to influence the equivalent inductance of an original coil; on the other hand, the resistance in the metal causes energy consumption, and affects the equivalent resistance of the primary coil. When the distance between the probe and the target board changes, the strength of the eddy current effect changes, the equivalent inductance and the resistance of the probe change, and the distance between the probe and the target board can be obtained after circuit processing. The three inductive sensor sensitive elements are all coils, and all generate a high-frequency magnetic field through a high-frequency excitation probe, and detect coil impedance or voltage change to detect other physical quantities such as displacement and the like.

When the environmental temperature changes, the resistivity of the coil of the inductive sensor changes, and the probe structure can also slightly deform, so that the output of the sensor changes. Generally, the output of the sensor is affected by temperature, and the way and the degree of the effect on different sensors are different, for example, for an eddy current sensor, when the temperature changes, the resistivity of a probe coil and a target plate changes, on one hand, the equivalent resistance of the probe is directly affected, on the other hand, the resistance changes to cause the size change of the eddy current, so that the size change of a reverse magnetic field also can be caused, and the changes have certain effect on the output of the sensor.

For a high-precision sensor or a case where the environmental temperature changes greatly, the influence of the temperature cannot be ignored. The sensor output can be compensated by measuring the temperature, so that the true physical quantity is obtained. In general, temperature compensation can be performed by additionally placing a temperature sensor in the environment, as shown in fig. 1, but this method has the following disadvantages: firstly, the temperature sensor additionally arranged measures the temperature at the temperature sensor, not the temperature of the coil, when the ambient temperature gradient is large, the temperature measurement is not accurate, and the compensation effect is not good, for example, in the case shown in fig. 1, the temperature at the position of the temperature measurement probe is higher than the temperature of the probe, and the accurate compensation cannot be realized; secondly, additional space is needed for a temperature sensor probe, a lead wire, a signal conditioning circuit and the like, and the complexity of the system is increased.

Disclosure of Invention

1. Technical problem to be solved

Aiming at the problems of poor precision and complex system in the prior art, the invention provides the sensor environment temperature measuring circuit and the sensor, which have high integration degree and compact structure, can accurately reflect the temperature at a measuring point and have better compensation effect.

2. Technical scheme

The purpose of the invention is realized by the following technical scheme.

The invention adds the probe resistance measuring circuit in the existing inductive sensor circuit, reflects the coil temperature through the probe resistance and compensates, and the proposal can accurately reflect the temperature at the measuring point and obtain better compensation effect. The scheme has high integration degree, compact structure and convenient installation.

A sensor environment temperature measuring circuit comprises a loop formed by a probe and an excitation source, and also comprises a direct current bias circuit and a divider resistor, wherein the direct current bias circuit and the divider resistor are superposed or externally added on the loop formed by the probe and the excitation source;

and the compensation circuit is arranged between the probe and the voltage dividing resistor and used for voltage compensation.

Furthermore, the dc bias circuit is an adder circuit formed by a dc voltage source or an operational amplifier directly connected in series to the ac excitation source, and superimposes a dc voltage on an ac voltage.

Furthermore, the compensation circuit comprises a low-pass filter circuit, an amplifying circuit, a compensation circuit and a demodulation circuit which are arranged in sequence. And forming a compensation loop for voltage compensation.

Furthermore, the low-pass filter circuit is formed by a filter resistor and a grounding capacitor which are connected in series on the loop. Low-pass filtering is carried out, and the next step of amplification is carried out after filtering.

Furthermore, the impedance of the filter resistor is far larger than that of the probe. The influence of shunting on displacement measurement is avoided.

Furthermore, the demodulation circuit further comprises a blocking capacitor, and the blocking capacitor is arranged at the front end of the demodulation circuit. To exclude direct current effects.

Furthermore, the voltage dividing resistor is a low-temperature drift resistor. The low temperature drift coefficient can avoid the temperature drift at the conditioning circuit from influencing the temperature measurement of the probe, and the size of the low temperature drift coefficient is determined according to the parameters of the probe.

Furthermore, the voltage dividing resistors are one or more groups. Different groups of voltage dividing resistors are adopted according to the single probe or the differential eddy current sensor, and one group or a plurality of groups can be formed.

Further, when the probe of the differential transformer type sensor excites the coil, voltage division compensation is performed on a voltage division resistor and a direct current resistor of the probe exciting coil.

A sensor comprises the environment temperature measuring circuit.

3. Advantageous effects

Compared with the prior art, the invention has the advantages that:

direct current excitation is directly applied to the inductive sensor coil, the resistance of the probe coil is effectively utilized for temperature measurement, and the temperature of a displacement measurement point can be directly measured, so that the temperature measurement is more accurate, the inductive sensor coil is suitable for high-precision application, and the inductive sensor coil is more rapid in response to temperature change and suitable for environments with high temperature gradients and rapid temperature changes. The exciting circuit of the temperature measuring circuit adopts a low-temperature drift resistor, so that the influence of temperature change on the temperature measuring circuit is reduced, and the temperature measuring precision is improved; the input impedance of the detection circuit of the temperature measurement circuit is large enough to avoid influencing displacement measurement. Because the probe coil is used as a temperature measuring element, the temperature measuring circuit has fewer components, high integration degree and compact structure. When the sensor is installed, the temperature compensation can be completed only by installing the displacement sensor probe, no difference is generated between the installation and the use of the common sensor without the temperature compensation, and additional wiring and installation of an additional temperature sensor probe are not needed.

Drawings

FIG. 1 is a schematic diagram of a prior art sensor temperature compensation circuit configuration;

FIG. 2 is a schematic diagram of a measurement circuit with a DC path present;

FIG. 3 is a schematic diagram of a measurement circuit without a DC path;

FIG. 4 is a schematic view of a measurement circuit according to embodiment 1;

FIG. 5 is a schematic view of a measurement circuit according to embodiment 2;

FIG. 6 is a schematic diagram of a measurement circuit according to embodiment 3.

Detailed Description

The invention is described in detail below with reference to the drawings and specific examples.

The inductance type sensor converts the measured non-electricity quantity such as displacement, pressure, flow, vibration and the like into the change of coil self-inductance quantity L or mutual inductance quantity M by utilizing the electromagnetic induction principle, and then the change is converted into the change quantity of voltage or current by a measuring circuit to be output.

According to the scheme, the probe resistance measuring circuit is added in the existing inductive sensor circuit, the temperature of the coil is reflected through the probe resistance and compensated, and the problems of inaccurate temperature measurement and complex system of an additionally arranged temperature sensor are solved.

According to the scheme, the temperature of the environment where the probe is located is detected through the resistance change of the detection coil by giving direct current excitation to the coil. There are two ways depending on the circuit form.

For the condition that a direct current path exists in the circuit, a direct current bias can be directly superposed on an excitation source of the inductive sensor, and a resistor is used for voltage division, as shown in fig. 2, an original inductive sensor excitation source V1 and a probe form a sampling loop, and detection is carried out under the condition that the probe is excited.

For the circuit without a direct current path originally, such as the circuit provided with a capacitor or other components, a direct current bias and voltage dividing resistor can be additionally arranged, as shown in fig. 3, a resistor R1 and a direct current bias circuit V2 are additionally arranged between the probe and the excitation source, and the circuit provided with a compensation loop direct current path is arranged.

In the two modes, V2 is divided by R1 and coil resistor Rx to obtain voltage Vx at the reaction temperature, which is V2 Rx/(Rx + R1), and the voltage is amplified and then enters a temperature compensation circuit, wherein Rx changes and Vx changes when the temperature at the probe changes, and the compensation circuit performs compensation according to the change of the voltage. The R1 in the circuit should use low temperature drift resistance to ensure that it is less affected by temperature and avoid the temperature change at the conditioning circuit from affecting the probe temperature measurement. The input impedance of the low-pass filter in the circuit is far larger than the impedance of the probe, so that the influence on displacement measurement caused by shunting from the probe is avoided. The ac impedance of V2 in the circuit of the second mode is much larger than the probe impedance, so as to avoid shunting from the probe, and can be realized by feedback.

In the scheme, a direct current part of an excitation source does not generate a high-frequency magnetic field, only divides voltage on R1 and the internal resistance of the probe and is used for measuring temperature, an alternating current part is used for measuring displacement, and the two parts are linearly superposed, are orthogonal to each other, do not interfere with each other and can be used for measuring respectively. The scheme has wide applicability, can be suitable for various inductive sensors, and can be used for a single-probe sensor and a differential sensor.

Example 1

As shown in fig. 4, this embodiment is an application of the present invention to a single-probe eddy current sensor. The displacement measuring circuit consists of an excitation source V1, a detection bridge and a demodulation circuit, wherein an alternating current excitation voltage V1 is divided on the R1 and the probe, the amplitude and the phase of the alternating current voltage change along with the change of the distance between the probe and the target plate, and the displacement information can be obtained by processing the voltage. The method is characterized in that a DC bias V2 is added at an excitation end by using an operational amplifier, the DC bias circuit is a DC voltage source directly connected in series with an AC excitation source or an addition circuit formed by the operational amplifier, the DC voltage is superposed on the AC voltage, the addition circuit is a conventional technology, the description is omitted, the DC voltage can be superposed on the AC voltage as long as the DC voltage is ensured, the DC voltage is divided on a resistor R1 of a bridge and a DC resistor of a probe, the DC voltage is amplified after low-pass filtering, and a resistor R2 and a grounding capacitor C2 are used for forming low-pass filtering to obtain the voltage reflecting the temperature of the probe. R1 adopts a low temperature drift resistor, the low temperature drift coefficient can avoid the temperature drift at the conditioning circuit from influencing the temperature measurement of the probe, the size of the low temperature drift coefficient is determined according to the parameters of the probe, and R1 is a low temperature drift resistor of 330 omega and 10 ppm/DEG C in the embodiment; the input impedance of the filter is far greater than the impedance of the probe, so that the influence of shunting on displacement measurement is avoided, and a 220k omega resistor R2 is adopted as a filter resistor in the embodiment; a DC blocking capacitor C1 is added to the front end of the demodulation circuit to eliminate the DC effect. The temperature compensation is carried out in the mode, the direct current part of the compensation excitation source does not generate a high-frequency magnetic field, only divides voltage on R1 and the internal resistance of the probe and is used for measuring temperature, the alternating current part is used for measuring displacement, the two parts are linearly superposed and mutually orthogonal without mutual interference and can be used for measuring respectively. The compensation circuit and the demodulation circuit may be corresponding circuits in the prior art, and are not described herein in detail.

Because the exciting circuit of the temperature measuring circuit adopts the resistance with low temperature drift, the influence of temperature change on the exciting circuit is reduced, and the precision of temperature measurement is improved; and a probe coil is adopted as a temperature measuring element, and temperature measuring circuit components are fewer, the integration degree is high, and the structure is compact. When the sensor is installed, the temperature compensation can be completed only by installing or replacing the displacement sensor probe, no difference is generated between the installation and the use of the common sensor without the temperature compensation, and additional wiring and installation of an additional temperature sensor probe are not needed.

Example 2

As shown in fig. 5, this embodiment is an application of the present invention to a differential eddy current sensor. The measuring circuit consists of an excitation source V1, a detection bridge and a demodulation circuit, wherein alternating current excitation voltage V1 is divided into voltage on the R1 and the probe 1 and voltage on the R3 and the probe 2, the amplitude and the phase of the two voltages are changed along with the change of the distance between the probe and the target plate, and the displacement information can be obtained by subtracting the two voltages and demodulating the two voltages. And a direct current bias V2 is added at the excitation end, the direct current voltage is divided on a resistor R1 of the bridge and a direct current resistor of the probe 1, and the voltage is amplified after low-pass filtering to obtain a voltage reflecting the temperature of the probe. R1 and R3 adopt low temperature drift resistors, the low temperature drift coefficient can avoid the temperature drift at the conditioning circuit from influencing the temperature measurement of the probe, and the size of the low temperature drift coefficient is determined according to the parameters of the probe, wherein in the embodiment, R1 and R3 are 51 omega, and the low temperature drift resistors are 10 ppm/DEG C; the input impedance of the filter is far greater than the impedance of the probe, so that the influence of shunting on displacement measurement is avoided, and a 220k omega resistor R2 is adopted as a filter resistor in the embodiment; a DC blocking capacitor is added to the front end of the demodulation circuit to eliminate the DC influence.

Example 3

This embodiment is an application of the present invention to a differential transformer sensor. The present embodiment uses the exciting coil of the differential transformer type sensor as the temperature measuring element. A direct current bias V2 and a voltage dividing resistor R1 are added at the excitation end, the direct current voltage is divided on a resistor R1 and the direct current resistor of the probe excitation coil, and the voltage is amplified after low-pass filtering to obtain the voltage reflecting the temperature of the probe. Wherein R1 should use low temperature drift resistance to avoid the temperature drift at the conditioning circuit from affecting the temperature measurement of the probe; the input impedance of the filter is far larger than the impedance of the probe, so that the influence of shunting on displacement measurement is avoided.

The compensation modes of the sensors are just some modes, and other types are compensation of inductive sensors. The method can be adopted after corresponding amplification and filtering by increasing direct current bias, is simple, has small change if a replacement mode is adopted, does not increase the volume, and has low cost and good effect.

The corresponding sensor including the measuring circuit of any of embodiments 1-3 is within the scope of our protection, and the probe resistance measuring circuit is added to the inductive sensor circuit.

The invention and its embodiments have been described above schematically, without limitation, and the invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The representation in the drawings is only one of the embodiments of the invention, the actual construction is not limited thereto, and any reference signs in the claims shall not limit the claims concerned. Therefore, if a person skilled in the art receives the teachings of the present invention, without inventive design, a similar structure and an embodiment to the above technical solution should be covered by the protection scope of the present patent. Furthermore, the word "comprising" does not exclude other elements or steps, and the word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. Several of the elements recited in the product claims may also be implemented by one element in software or hardware. The terms first, second, etc. are used to denote names, but not any particular order.

Claims

1. A sensor environment temperature measuring circuit comprises a loop formed by a probe and an excitation source, and is characterized by also comprising a direct current bias circuit and a divider resistor, wherein the direct current bias circuit and the divider resistor are superposed or externally added on the loop formed by the probe and the excitation source;

2. The ambient temperature sensor measurement circuit of claim 1, wherein the dc bias circuit is an adder circuit comprising a dc voltage source or an operational amplifier directly connected in series with the ac excitation source, and wherein the dc voltage is superimposed on the ac voltage.

3. The sensor environment temperature measuring circuit of claim 1, wherein the compensation circuit comprises a low-pass filter circuit, an amplifier circuit, a compensation circuit and a demodulator circuit arranged in sequence.

4. The sensor environment temperature measurement circuit of claim 3, wherein the low pass filter circuit is formed by a filter resistor and a ground capacitor connected in series on the loop.

5. The sensor ambient temperature measurement circuit of claim 4, wherein the filter resistor impedance is substantially greater than the probe impedance.

6. The sensor environment temperature measurement circuit of claim 3, further comprising a dc blocking capacitor disposed at a front end of the demodulation circuit.

7. The sensor environment temperature measurement circuit according to claim 1, wherein the voltage dividing resistor is a low temperature drift resistor.

8. The ambient temperature sensor measurement circuit of claim 1, wherein the voltage dividing resistors are one or more groups.

9. The sensor environment temperature measuring circuit according to any one of claims 1 to 8, wherein voltage division compensation is performed on a voltage dividing resistor and a direct current resistor of the probe exciting coil when the probe exciting coil of the differential transformer type sensor is excited.

10. A sensor according to claim 1, characterized in that the sensor comprises an ambient temperature measuring circuit according to any of claims 1-9.