A precision temperature measurement and control device based on a pre - placed AC bridge

Abstract

The present invention discloses a precise temperature measurement and control device based on a pre - placed AC bridge. The device includes a temperature control and temperature fluctuation measurement module, an actuator driving module, and a controlled object module. Aiming at improving the temperature control accuracy and temperature stability of the temperature measurement and control device, an AC Wheatstone bridge and a subsequent digital demodulation link are adopted to reduce the noise of the front - end amplifier. Additionally, the entire Wheatstone bridge is uniquely moved to the controlled object end, and the temperature fluctuation measurement circuit and the temperature control circuit are placed on the same circuit board. This temperature measurement and control device has higher temperature control accuracy, greatly improves the stability and anti - interference ability of the system, reduces the residual temperature noise after the temperature control system operates stably in a closed - loop manner, and thus improves the temperature stability of the temperature measurement and control device after temperature control.

Description

Technical Field

[0001] The present invention relates to the technical field of high-precision signal measurement and control, and particularly to a precision temperature measurement and control device based on a preposed alternating current bridge. Background Art

[0002] Temperature control systems have been widely used in scientific research and industrial precision instruments. In some special application scenarios, in order to ensure the stable operation of core devices, a high-precision and low-noise temperature control system is required to provide a stable temperature environment for them. For example, in a laser frequency stabilization system, the temperature stability of the frequency reference is an important factor affecting the frequency stability. For example, the temperature change of the optical cavity serving as the frequency reference will cause a change in its cavity length, resulting in a drift of the laser frequency, and further affecting the long-term stability of the laser frequency. Therefore, researching a high-precision and low-temperature-noise temperature control device has important functions and significance for scientific research including ultra-stable lasers.

[0003] After the temperature control system operates stably in a closed loop, the temperature noise inside and outside the loop starts to rise in the low-frequency part, mainly due to the output noise of the Wheatstone bridge temperature sensor and the noise of the subsequent amplifier, especially the low-frequency components among them. In the prior art, generally only the temperature-sensitive device (thermistor) is placed at the temperature control point, and the noise brought by its wire resistance and parasitic capacitance cannot be ignored, which greatly affects the noise in the low-frequency part of the precision temperature control system. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a precision temperature measurement and control device based on a preposed alternating current bridge.

[0005] The technical solution adopted by the present invention to solve the technical problems is as follows:

[0006] A precision temperature measurement and control device based on a preposed alternating current bridge includes an AC excitation source, and also includes a temperature fluctuation measurement circuit, a temperature control circuit, an actuator drive module, an actuator, a temperature control bridge, and a temperature measurement bridge, wherein the temperature control bridge and the temperature measurement bridge are Wheatstone bridges;

[0007] The temperature fluctuation measurement circuit includes a first amplifier, the output end of the first amplifier is connected to the modulation input end of a first synchronous demodulator, the output end of the first synchronous demodulator is connected to the input end of a first low-pass filter, and the output end of the first low-pass filter is connected to an out-of-loop temperature signal output end;

[0008] The temperature control circuit includes a second amplifier, the output end of the second amplifier is connected to the modulation input end of a second synchronous demodulator, the output end of the second synchronous demodulator is connected to the input end of a second low-pass filter, and the output end of the second low-pass filter is respectively connected to an in-loop temperature signal output end and the input end of a PID module;

[0009] The output terminal of the PID module is connected to the actuator for adjusting the temperature through the actuator drive module;

[0010] Both the temperature control bridge and the temperature measurement bridge are located on the controlled object;

[0011] The AC excitation source provides AC power to the first synchronous demodulator, the second synchronous demodulator, the temperature control bridge, and the temperature measurement bridge respectively;

[0012] The differential signal of the temperature measurement bridge and the differential signal of the temperature control bridge are respectively input to the input terminal of the first amplifier and the input terminal of the second amplifier.

[0013] As described above, the temperature control bridge includes a first reference resistor, a second reference resistor, a first temperature setting resistor, and a first thermistor. The first reference resistor and the second reference resistor are connected in series to form the fixed arm of the temperature control bridge, and the first temperature setting resistor and the first thermistor are connected in series to form the measuring arm of the temperature control bridge. The fixed arm of the temperature control bridge is connected in parallel with the measuring arm of the temperature control bridge; the differential signal between the connection point A between the first reference resistor and the second reference resistor and the connection point B between the first temperature setting resistor and the first thermistor is input to the input terminal of the second amplifier;

[0014] The temperature measurement bridge includes a third reference resistor, a fourth reference resistor, a second temperature setting resistor, and a second thermistor. The third reference resistor and the fourth reference resistor are connected in series to form the fixed arm of the temperature measurement bridge, and the second temperature setting resistor and the second thermistor are connected in series to form the measuring arm of the temperature measurement bridge. The fixed arm of the temperature measurement bridge is connected in parallel with the measuring arm of the temperature measurement bridge; the differential signal between the connection point C between the third reference resistor and the fourth reference resistor and the connection point D between the second temperature setting resistor and the second thermistor is input to the input terminal of the first amplifier.

[0015] As described above, the resistance values of the first reference resistor, the second reference resistor, the third reference resistor, the fourth reference resistor, the first temperature setting resistor, and the second temperature setting resistor are the same.

[0016] As described above, the temperature fluctuation measurement circuit and the temperature control circuit are placed on the same circuit board, and the circuit board is placed on the controlled object.

[0017] As described above, the controlled object is a frequency-stabilized reference optical cavity.

[0018] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0019] 1. The present invention places an AC Wheatstone bridge (including temperature-sensitive devices) in front of the controlled object. This structure not only reduces the temperature noise of the fixed resistors in the bridge, but also reduces the influence of the resistance and parasitic capacitance in the wires of the temperature-sensitive devices in the unbalanced bridge on temperature measurement and control, greatly improving the low-frequency noise of the temperature measurement and control device. As a result, the temperature stability and anti-interference ability of the temperature measurement and control device after temperature control are improved, and it can achieve an equivalent temperature noise spectrum of less than 4 μK / Hz in the frequency range of 1 mHz to 1 Hz. 1 / 2 。

[0020] 2. The device places the temperature fluctuation measurement circuit and the temperature control circuit on the same circuit board. The temperature fluctuation measurement circuit reduces the noise during the measurement process and accurately measures the temperature fluctuation outside the control loop of the temperature measurement and control device. The temperature measurement and control device achieves high-precision temperature control. The device improves the low-frequency noise in temperature measurement and control and enhances the long-term stability of the temperature measurement and control device. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is the principle structure diagram of the present invention;

[0022] Figure 2 The equivalent temperature noise curve at the input end of the temperature fluctuation measurement circuit (measured by replacing the temperature-measuring thermistor with a fixed resistor);

[0023] Where:

[0024] 1 - Temperature control and temperature fluctuation measurement module; 11 - Temperature fluctuation measurement circuit; 12 - Temperature control circuit; 101 - AC excitation source; 111 - First amplifier; 112 - First synchronous demodulator; 113 - First low-pass filter; 121 - Second amplifier; 122 - Second synchronous demodulator; 123 - Second low-pass filter; 124 - PID module;

[0025] 2 - Actuator drive module;

[0026] 3 - Controlled object module; 31 - Actuator; 32 - Temperature-measuring bridge; 33 - Temperature-control bridge;

[0027] R1 to R4 - First reference resistor to fourth reference resistor;

[0028] R set1 ~R set2 - First temperature setting resistor to second temperature setting resistor;

[0029] R t1 ~R t2 - First thermistor to second thermistor. DETAILED DESCRIPTION OF THE INVENTION

[0030] For the convenience of those of ordinary skill in the art to understand and implement the present invention, the present invention will be further described in detail below in conjunction with embodiments and with reference to the accompanying drawings. The embodiments described herein are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

[0031] In order to achieve high-stability precision temperature control, the present invention places the circuit board of the AC Wheatstone bridge in front of the controlled object, and at the same time uses a synchronous demodulator for phase-locked amplification, reducing the output noise of the temperature sensor and the 1 / f noise input to the front-end amplifier, improving the low-frequency characteristics of the temperature measurement and control device, enhancing the long-term stability of the temperature measurement and control device, and further improving the long-term stability of the temperature of the controlled object after temperature control.

[0032] As Figure 1 shown, a precision temperature measurement and control device based on a pre-positioned AC bridge includes a temperature control and temperature fluctuation measurement module 1, an actuator drive module 2, and a controlled object module 3. Among them, one end of the actuator drive module 2 is connected to the temperature control and temperature fluctuation measurement module 1, and the other end is connected to the controlled object module 3.

[0033] The temperature control and temperature fluctuation measurement module 1 includes a temperature fluctuation measurement circuit 11, a temperature control circuit 12, and an AC excitation source 101.

[0034] The controlled object module 3 includes an actuator 31, a temperature control bridge 33, and a temperature measurement bridge 32. Both the temperature control bridge 33 and the temperature measurement bridge 32 are Wheatstone bridges.

[0035] The AC excitation source 101 provides AC power for the temperature fluctuation measurement circuit 11, the temperature control circuit 12, the temperature measurement bridge 32, and the temperature control bridge 33 respectively.

[0036] The temperature fluctuation measurement circuit 11 includes a first amplifier 111, a first synchronous demodulator 112, and a first low-pass filter 113. The first amplifier 111, the first synchronous demodulator 112, and the first low-pass filter 113 are connected in sequence, that is, the output end of the first amplifier 111 is connected to the modulation input end of the first synchronous demodulator 112, the output end of the first synchronous demodulator 112 is connected to the input end of the first low-pass filter 113, and the output end of the first low-pass filter 113 is connected to the out-of-loop temperature signal output end.

[0037] The temperature control circuit 12 includes a second amplifier 121, a second synchronous demodulator 122, a second low-pass filter 123, and a PID module 124. The second amplifier 121, the second synchronous demodulator 122, and the second low-pass filter 123 are connected in sequence, that is, the output end of the second amplifier 121 is connected to the modulation input end of the second synchronous demodulator 122, and the output end of the second synchronous demodulator 122 is connected to the input end of the second low-pass filter 123. The output end of the second low-pass filter 123 is connected to the output end of the in-loop temperature signal, and in addition, the output end of the second low-pass filter 123 is also connected to the input end of the PID module 124. The output end of the PID module 124 outputs a control signal to the actuator drive module 2.

[0038] The input of the actuator drive module 2 is the control signal output by the PID module 124 in the temperature control circuit 12. The output of the actuator drive module 2 acts on the actuator 31 in the controlled object module 3, thereby changing the heat supplied to or absorbed by the controlled object module 3 to achieve the purpose of temperature adjustment.

[0039] The actuator 31 is located around the controlled object (the controlled object is the frequency-stabilized reference optical cavity used for frequency stabilization) and is in good thermal contact with the controlled object. The temperature control bridge 33 and the temperature measurement bridge 32 are also placed on the controlled object.

[0040] The temperature control bridge 33 includes a first reference resistor R1, a second reference resistor R2, a first temperature setting resistor R set1 and a first thermistor R t1 . The first reference resistor R1 and the second reference resistor R2 are connected in series to form the fixed arm of the control bridge 33. The temperature setting resistor R set1 and the thermistor R t1 are connected in series to form the measuring arm of the temperature control bridge 33. The first thermistor R t1 is used to measure the in-loop temperature of the controlled object, that is, the control temperature of the controlled object. After the fixed arm of the temperature control bridge 33 and the measuring arm of the temperature control bridge 33 are connected in parallel, they are connected in parallel with the AC excitation source 101 to form an AC Wheatstone bridge for measuring the control temperature of the controlled object. The differential signal between the connection point (point A) between the first reference resistor R1 and the second reference resistor R2 and the connection point (point B) between the first temperature setting resistor R set1 and the first thermistor R t1 is input to the second amplifier 121.

[0041] The temperature measurement bridge 32 includes a third reference resistor R3, a fourth reference resistor R4, a second temperature setting resistor R set2 and a second thermistor R t2。The third reference resistor R3 and the fourth reference resistor R4 are connected in series to form the fixed arm of the temperature-measuring bridge 32. The second temperature-setting resistor R set2 and the second thermistor R t2 are connected in series to form the measuring arm of the temperature-measuring bridge 32. The second thermistor R t2 is used to measure the temperature fluctuation outside the loop of the controlled object, that is, the actual temperature fluctuation of the controlled object. After the fixed arm of the temperature-measuring bridge 32 is connected in parallel with the measuring arm of the temperature-measuring bridge 32, it is connected in parallel with the AC excitation source 101 to form an AC Wheatstone bridge for measuring the actual temperature of the controlled object. The connection point (point C) between the third reference resistor R3 and the fourth reference resistor R4 and the second temperature-setting resistor R set2 and the connection point (point D) between the second thermistor R t2 The differential signal between them is input to the first amplifier 111.

[0042] In addition, the AC excitation source 101, the temperature control bridge 33, and the temperature-measuring bridge 32 are grounded.

[0043] The first synchronous demodulator 112 in the temperature fluctuation measurement circuit 11 demodulates the modulated differential signal in the temperature-measuring bridge 32, and finally outputs a first DC error signal through the first low-pass filter 113. The first DC error signal is output to the temperature signal output terminal outside the loop for measuring the temperature outside the loop. The second synchronous demodulator 122 in the temperature control circuit 12 demodulates the modulated differential signal in the temperature control bridge 33, and then outputs a second DC error signal through the second low-pass filter 123. The second DC error signal is respectively input to the temperature signal output terminal inside the loop and the input terminal of the PID module 124. Using the first synchronous demodulator 112 and the second synchronous demodulator 122 for phase-locked amplification reduces the output noise of the temperature sensor and the 1 / f noise input to the front-end amplifier, improves the low-frequency characteristics in temperature measurement and control, and improves the long-term temperature stability of the controlled object after temperature control.

[0044] In this embodiment, the temperature fluctuation measurement circuit 11 and the temperature control circuit 12 are placed on the same circuit board, integrating the functions of measuring the temperature fluctuation outside the control loop and controlling the temperature inside the loop, and can be conveniently applied to various other embodiments.

[0045] In this embodiment, the first reference resistor R1, the second reference resistor R2, the third reference resistor R3, the fourth reference resistor R4, and the first temperature-setting resistor R set1 and the second temperature-setting resistor R set2They have the same resistance value and use resistors with a low temperature coefficient to reduce the influence of temperature changes on the temperature measurement bridge 32 and the temperature control bridge 33. In this embodiment, a low-temperature-drift high-precision resistor (SJ102C, Vishay Technology) with a temperature drift coefficient of 2 ppm / K and a resistance value accuracy of 0.01% is adopted. The temperature measurement bridge 32 and the temperature control bridge 33 are both arranged on the controlled object to minimize the influence of ambient temperature changes on the temperature measurement bridge 32 and the temperature control bridge 33, and at the same time avoid the influence of the wire resistance and parasitic capacitance of the thermistor on temperature measurement and control when only the thermistor is placed on the controlled object.

[0046] In this embodiment, the first reference resistor R1 and the second reference resistor R2 use twin resistors with a resistance value of 10 kΩ, and the third reference resistor R3 and the fourth reference resistor R4 also use twin resistors with a resistance value of 10 kΩ. The first temperature setting resistor R set1 and the second temperature setting resistor R set2 are set as low-temperature-drift resistors with a resistance value of 10 kΩ. The first thermistor R t1 and the second thermistor R t2 are replaced with low-temperature-drift resistors with a resistance value of 10 kΩ. The temperature measurement circuit in the temperature control and temperature fluctuation measurement module 1 is used to measure the temperature fluctuation. Figure 2 This is the equivalent temperature noise spectrum curve at the input end of the temperature fluctuation measurement device of the present invention in the frequency band of 1 mHz to 10 Hz. The abscissa is the frequency, with the unit of Hz; the ordinate is the temperature noise, with the unit of K / Hz 1 / 2 ; The present invention can achieve an equivalent temperature noise spectrum of less than 4 μK / Hz in the frequency range of 1 mHz to 1 Hz 1 / 2 .

[0047] The present invention is not limited to the above embodiments. The above embodiments only describe the preferred embodiments of the present invention and do not limit the concept of the present invention. The implementation schemes in the above embodiments can be further combined or replaced. All changes and improvements made by those skilled in the art to the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A precision temperature measurement and control device based on a pre - placed AC bridge, comprising an AC excitation source (101), characterized in that, It also includes a temperature fluctuation measurement circuit (11), a temperature control circuit (12), an actuator drive module (2), an actuator (31), a temperature control Wheatstone bridge (33) and a temperature measurement Wheatstone bridge (32), wherein the temperature control Wheatstone bridge (33) and the temperature measurement Wheatstone bridge (32) are Wheatstone bridges; The temperature fluctuation measurement circuit (11) includes a first amplifier (111), the output end of the first amplifier (111) is connected to the modulation input end of the first synchronous demodulator (112), the output end of the first synchronous demodulator (112) is connected to the input end of the first low-pass filter (113), and the output end of the first low-pass filter (113) is connected to the out-of-loop temperature signal output end; The temperature control circuit (12) includes a second amplifier (121), the output end of the second amplifier (121) is connected to the modulation input end of the second synchronous demodulator (122), the output end of the second synchronous demodulator (122) is connected to the input end of the second low-pass filter (123), and the output end of the second low-pass filter (123) is respectively connected to the in-loop temperature signal output end and the input end of the PID module (124); The output end of the PID module (124) is connected to the actuator (31) for adjusting the temperature through the actuator drive module (2); Both the temperature control Wheatstone bridge (33) and the temperature measurement Wheatstone bridge (32) are located on the controlled object; The AC excitation source (101) provides AC power for the first synchronous demodulator (112), the second synchronous demodulator (122), the temperature control Wheatstone bridge (33) and the temperature measurement Wheatstone bridge (32) respectively; The differential signal of the temperature measurement Wheatstone bridge (32) and the differential signal of the temperature control Wheatstone bridge (33) are respectively input to the input end of the first amplifier (111) and the input end of the second amplifier (121).

2. The precision temperature measurement and control device based on a preposed AC bridge according to claim 1, wherein, The temperature control bridge (33) includes a first reference resistor (R1), a second reference resistor (R2), a first temperature setting resistor (R set1 ), and a first thermistor (R t1 ). The first reference resistor (R1) and the second reference resistor (R2) are connected in series to form the fixed arm of the temperature control bridge (33). The first temperature setting resistor (R set1 ) and the first thermistor (R t1 ) are connected in series to form the measuring arm of the temperature control bridge (33). The fixed arm of the temperature control bridge (33) is connected in parallel with the measuring arm of the temperature control bridge (33). The connection point A between the first reference resistor (R1) and the second reference resistor (R2) and the connection point B between the first temperature setting resistor (R set1 ) and the first thermistor (R t1 ) are inputted with a differential signal to the input end of the second amplifier (121); The temperature-measuring bridge (32) includes a third reference resistor (R3), a fourth reference resistor (R4), a second temperature-setting resistor (R set2 ), and a second thermistor (R t2 ). The third reference resistor (R3) and the fourth reference resistor (R4) are connected in series to form the fixed arm of the temperature-measuring bridge (32). The second temperature-setting resistor (R set2 ) and the second thermistor (R t2 ) are connected in series to form the measuring arm of the temperature-measuring bridge (32). The fixed arm of the temperature-measuring bridge (32) is connected in parallel with the measuring arm of the temperature-measuring bridge (32). The connection point C between the third reference resistor (R3) and the fourth reference resistor (R4) and the connection point D between the second temperature-setting resistor (R set2 ) and the second thermistor (R t2 ) are inputted with the differential signal to the input end of the first amplifier (111).

3. The precision temperature measurement and control device based on a preposed AC bridge according to claim 2, characterized in that, The first reference resistor (R1), the second reference resistor (R2), the third reference resistor (R3), the fourth reference resistor (R4), and the first temperature setting resistor (R set1 ) and the second temperature setting resistor (R set2 ) have the same resistance value.

4. The precision temperature measurement and control device based on a pre - placed AC bridge according to claim 1, characterized in that, The temperature fluctuation measurement circuit (11) and the temperature control circuit (12) are placed on the same circuit board, and the circuit board is placed on the controlled object.

5. The precision temperature measurement and control device based on a preposed AC bridge according to claim 1, characterized in that, The controlled object is a frequency-stabilized reference optical cavity.

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