CN205581683U - A high accuracy temperature control system for optics microballon chamber - Google Patents

Abstract

The utility model discloses a high-precision temperature control system for an optical microsphere cavity, which includes an AT89C52 single-chip microcomputer, an A/D conversion circuit, an anti-aliasing filter circuit, an instrument amplifier circuit, a constant current source, a PT1000 temperature sensor, and a refrigeration unit. And heating sheet, driving circuit, display module, keyboard module and power supply module. The high-precision measurement of temperature adopts the temperature measurement scheme of micro-current driven four-wire platinum resistance Pt1000, and uses anti-interference filtering technology to reduce noise, suppress interference, reduce system errors, and improve the measurement accuracy and stability of the system. Constant temperature control, which is generated by the single-chip microcomputer based on the Fuzzy-intelligent PID composite control algorithm result command drive circuit, controls the cooling or heating plate to regulate the temperature inside the mechanical package of the optical microsphere cavity. The high-precision temperature control system provided by the utility model has the characteristics of high precision, good reliability, stability and practicability, and can effectively simplify the production and use procedures of the optical microsphere cavity.

Description

A high-precision temperature control system for optical microsphere cavity

technical field

The utility model relates to the field of intelligent control, in particular to a high-precision temperature control system for an optical microsphere cavity.

Background technique

The thermal expansion coefficient and thermo-optic effect of the optical microsphere cavity material are sensitive to the ambient temperature. The external temperature change or the absorption of laser energy will cause the thermal expansion of the material; the thermal expansion and thermo-optic effect of the material lead to the change of the resonant cavity size and the refractive index respectively, eventually causing Resonant frequency changes; at present, in order to reduce the influence of ambient temperature on the performance of the optical microsphere cavity, the microsphere cavity is mainly packaged with ultraviolet glue, and the thickness of the ultraviolet glue is changed to change the proportion of light in the ultraviolet glue to adjust the temperature. coefficient; this method is cumbersome to calculate, high in cost, complex in selecting devices, and requires precise control of the coating characteristics of UV glue.

The optical microsphere cavity is sensitive to temperature. If the temperature in the optical microsphere cavity device can be precisely controlled, the temperature effect of the optical microsphere cavity can also be suppressed; Simplify the preparation procedure of the optical microsphere cavity, but require a high-precision temperature control system. A high-precision temperature control system requires high-precision measurement and constant temperature control. In ultra-high-precision measurement, mostly standard platinum resistance temperature sensors are used. Its measurement accuracy can reach 0.001°C, and the annual drift rate does not exceed 0.001°C; in platinum resistance temperature measurement, it is required to be supported by a constant current source with high precision and little influence from the ambient temperature. A highly stable constant current source becomes the key to high-precision measurement. When the constant current source is too large, it will cause the components such as resistors to heat up, produce self-heating effect, and cause errors; but if the current is too small, the signal-to-noise ratio is difficult to guarantee; SCR realizes the control of the heater and refrigerator, which requires an intelligent temperature monitoring algorithm to achieve constant temperature control.

Contents of the invention

The purpose of the utility model is to solve the problems in the prior art and provide a high-precision, high-reliability, stable and practical temperature control system for the optical microsphere cavity.

The high-precision temperature control system provided by the utility model includes: AT89C52 single-chip microcomputer, A/D conversion circuit, anti-aliasing filter circuit, instrument amplifier circuit, constant current source, PT1000 temperature sensor, refrigeration and heating chip, drive circuit, display module , keyboard module and power supply module.

The single-chip microcomputer adopts AT89C52 single-chip microcomputer, which is the control core of the whole temperature control system, including high-precision temperature measurement, temperature display and constant temperature control.

The A/D conversion circuit is the core device of the data collector, adopting the integrated chip AD7714 with 8 on-chip registers, through the programming of the on-chip registers, channel selection, gain selection, filter frequency selection, and conversion cycle selection can be realized , automatic calibration and AD conversion and other functions.

The anti-aliasing filter circuit includes a low-pass filter circuit and a sample-and-hold circuit; the low-pass filter circuit includes a resistor R and a capacitor C; the capacitor in the low-pass filter circuit is connected in parallel with the capacitor in the sample-and-hold circuit.

The instrument amplifier circuit is mainly composed of three operational amplifiers and seven resistors, and the voltage gain is adjusted by the resistors.

The constant current source is composed of 5V reference voltage source, impedance converter A1, voltage amplifiers A2 and A3, current amplifiers Q1, Q2, Q3, precision sampling resistor Rx and feedback signal voltage follower A4; it can provide 0.5mA constant current, the error range is less than 0.04%.

The PT1000 is a platinum resistance temperature sensor, which is placed near the optical microsphere cavity to measure the temperature of the microsphere cavity in real time.

In the cooling and heating sheet, the cooling sheet adopts a semi-conductor cooling sheet without mechanical vibration, and the heating sheet is a cermet heating sheet.

The driving circuit adopts BTS7960 chip to form a half-bridge driving circuit, which can change the ambient temperature of the optical microsphere cavity by sequentially driving the cooling and heating plates.

The display module includes an ST7920 Chinese graphics liquid crystal module driver controller and an LCD display screen, and with the cooperation of the ST7920 controller driver, a 256×32 dot matrix liquid crystal display can be realized.

The keyboard module includes a ZLG7290 keyboard scanning chip and an 8×8 keyboard, and is mainly used for setting the ambient temperature of the optical microsphere cavity.

The power supply module includes a series DC stabilized power supply composed of three-terminal integrated voltage regulators, rectification and filter circuits.

The beneficial effect of the utility model is that the provided high-precision temperature control system for the microsphere cavity can suppress the interference caused by the irregular change of the external environment temperature, and ensure the stability of the performance of the microsphere cavity; the temperature control method is simplified, and the cost of the experiment. The constant current source designed by the system can provide a highly stable 0.5mA current to ensure accurate real-time temperature measurement by the temperature sensor PT1000. The combination of instrument amplifier circuit, anti-aliasing filter circuit and high-precision A/D converter can reduce the influence of external interference on the measurement system. The constant temperature control adopts non-mechanical vibration semiconductor refrigeration chips and metal ceramic heating chips as temperature control elements, which can reduce temperature control errors and eliminate vibration interference; at the same time, it is combined with the Fuzzy-intelligent PID composite control algorithm to control the temperature of the microsphere cavity. Precision constant temperature control.

Description of drawings

Fig. 1 shows the block diagram of the high-precision temperature control system used in the optical microsphere cavity in the utility model.

Fig. 2 shows the connection circuit diagram of the A/D conversion circuit and the single-chip microcomputer in the utility model.

FIG. 3 is a circuit diagram of the anti-aliasing filter in the utility model.

Shown in Fig. 4 is the instrument amplifying circuit diagram in the utility model.

Fig. 5 shows the circuit diagram of the constant current source in the utility model.

Fig. 6 shows the schematic diagram of Fuzzy-intelligent PID composite control algorithm in the utility model.

Figure 7 shows the flow chart of the constant temperature control program in the utility model.

detailed description

Specific embodiments of the present utility model will be described in detail below in conjunction with specific drawings. It should be noted that the technical features or combinations of technical features described in the following embodiments should not be regarded as isolated, and they can be combined with each other to achieve better technical effects.

As shown in Figure 1, the high-precision temperature control system for the optical microsphere cavity provided by the utility model includes: a single-chip microcomputer 1, an A/D conversion circuit 2, an anti-aliasing filter circuit 3, an instrument amplifier circuit 4, and a constant Flow source 5, PT1000 temperature sensor 6, cooling and heating sheet 7, drive circuit 8, display module 9, keyboard module 10 and power module 11.

Single-chip microcomputer 1 adopts AT89C52 chip as the control core of the system, responsible for high-precision temperature measurement, temperature setting, temperature display and constant temperature control.

A/D conversion circuit 2 adopts 24-bit high-resolution integrated chip AD7714, which is the core device of the data collector and determines the measurement accuracy of the system. The connection circuit diagram with the single-chip microcomputer AT89C52 is shown in Figure 2.

Anti-aliasing filter circuit 3, the circuit design shown in Figure 3, is mainly used to attenuate and filter out some aliasing signals that will be collected during the data acquisition process of the temperature measurement system; the RC low composed of resistor R ₁₇ and capacitor C ₅ Pass filter circuit to filter out the interference signal greater than the cut-off frequency of the low-pass filter circuit 1/2πRC in the high-frequency signal; C ₆ is connected with the high-precision A/D conversion circuit, which can reduce the aperture error and give full play to the performance of the A/D converter , while filtering out high-frequency harmonics.

Instrument amplifier circuit 4, the design circuit is shown in Figure 4, mainly used for high-precision processing of weak signals.

Constant current source 5, the design circuit is shown in Figure 5, when the load resistance R _x becomes larger, the instantaneous voltage drop V _x on it increases accordingly, and the voltage between the non-inverting input terminal and the inverting input terminal of the operational amplifier A3 The voltage difference decreases, and the output voltage V2 is lower than the reference voltage. At this time, the inverting input terminal of the operational amplifier A2 generates a small negative voltage, and A2 linearly amplifies the voltage difference between its non-inverting input terminal and the inverting input terminal, and the output The positive voltage makes the emitter voltage of the transistor Q3 increase, thereby keeping the voltage drop on the precision sampling resistor unchanged; when the load resistance Rx decreases, the working process _is similar to the above.

PT1000 temperature sensor 6 is mainly used for high-precision temperature measurement. In order to eliminate the influence of platinum resistor lead resistance on measurement accuracy, PT1000 adopts a four-wire connection method.

The cooling and heating sheet 7 is used for heating or cooling the ambient temperature of the optical microsphere cavity.

The driving circuit 8 adopts the BTS7960 chip to form a half-bridge driving circuit, which can drive the cooling and heating chips in turn.

The display module 9 is used for temperature display and instruction state display.

The keyboard module 10 is mainly used for temperature preset and command input.

The power module 11 provides power for the system.

Example:

An embodiment of the present application provides a high-precision temperature control system for an optical microsphere cavity, including high-precision measurement and constant temperature control of the temperature in the mechanical package of the optical microsphere cavity.

When the system is running, first enter the expected value of the target temperature and the upper and lower limits through the keyboard, and at the same time start the temperature sensor PT1000 to monitor the temperature in the mechanical package of the optical microsphere cavity in real time and generate a corresponding voltage signal; the signal first enters the instrument amplifier circuit to remove common mode interference And carry out proper amplification, and then attenuate and filter the aliasing signal through the anti-aliasing filter circuit; then input the high-precision A/D conversion circuit; the digital signal after A/D conversion enters the single-chip microcomputer system for digital filtering, and the single-chip microcomputer performs digital filtering. The signal processing obtains the real temperature and compares it with the preset value; if the actual temperature is lower than the target temperature, the single-chip microcomputer sends an instruction to drive the heating plate to work to increase the temperature; otherwise, it drives the refrigeration circuit to work to reduce the temperature; finally, the display module 3 Display the temperature.

The temperature control method adopts Fuzzy-intelligent PID compound control algorithm, the algorithm is based on Fuzzy fuzzy control theory and intelligent PID control strategy, find out the control parameters K _p (proportional control factor), K _i (integral control factor), K _D (differential control factor) Factor) and the relationship between the input quantity e (the deviation between the target temperature and the measured temperature), e _c (the rate of change of the deviation of e), to realize the real-time correction of the three control parameters. First, the basic PID parameters are provided by the fuzzy controller of the input quantity, the state analysis is carried out according to the basic parameters, differential control items and the current state, and the PID parameters are intelligently corrected according to the analysis results; the schematic diagram is shown in Figure 6.

The flow chart of the control program is shown in Figure 7; the initialization is mainly to initialize the various devices and variables, and all parts of the system are ready; input the set temperature value and upper and lower limit temperatures (such as: 20±0.01 ⁰ C)) through the keyboard; start The temperature measurement circuit collects temperature; determines whether the temperature is equal to the expected temperature; if it is equal to the expected temperature, start the display module for temperature display; Perform temperature regulation, delay 10ms after regulation, and collect temperature again until the temperature is equal to the expected temperature, and display it.

The utility model provides a high-precision temperature control system for an optical microsphere cavity. Although the application has provided some embodiments of the utility model, those skilled in the art should understand that without departing from the utility model Changes may be made to the embodiments of the present application within the spirit of the invention. The above-mentioned embodiments are only exemplary, and the embodiments of the present application should not be used as limitations on the scope of rights of the present utility model.

Claims (2)

1. A high-precision temperature control system for optical microsphere cavity, including: AT89C52 single-chip microcomputer, A/D conversion circuit, anti-aliasing filter circuit, instrument amplifier circuit, constant current source, PT1000 temperature sensor, cooling and heating chip, drive circuit, display module, keyboard module and power supply module; The anti-aliasing filter circuit includes a low-pass filter circuit and a sample-and-hold circuit; the low-pass filter circuit includes a resistor R and a capacitor C; the capacitor in the low-pass filter circuit is connected in parallel with the capacitor in the sample-and-hold circuit; The instrument amplifier circuit is mainly composed of three operational amplifiers and seven resistors, and the voltage gain is adjusted by the resistors. 2. A kind of high-precision temperature control system for optical microsphere cavity according to claim 1, it is characterized in that, constant current source is made of 5V reference voltage source, impedance transformer A1, voltage amplifier A2 and A3, current amplifier Composed of Q1, Q2, Q3, precision sampling resistor Rx and feedback signal voltage follower A4; it can provide 0.5mA constant current, and the error range is less than 0.04%.