The Electrical Research And Realization Of The Temperature Calibrator

In productive practice in the modern, control instrument and the temperature display has been widely used in the production and life, the test of temperature technology has become an important subject, and temperature measurements are the precondition of accurate, efficient and productive of the factory safe. The signal of the temperature sensor is analog signal and digital signal, all in which programs or the circuit in the chip will have your temperature into. Therefore, the adjustment, corrections and maintenance of the moisture instrument is very important in the test.The furnace body of the temperature calibrator is liquid and solid. The advantage of the solid temperature is a wide range of temperature, small volume, light weight and fast heating-up and cooling. So, this text deeply research into the temperature calibrator for measuring range 50 to 400℃.Because the furnace body of the temperature calibrator is the constant temperature field in which a standard resistance and a calibrated temperature sensor are,the temperature field has the more constant demand.This designment adopts PWM heating way ,it satisfys this better requirement,which makes the input DC voltage to the output DC voltage.PWM heating way adjusts duty ratio to change the output of the DC voltage, thus change current of electric wire, and temperature of the furnace body, to achieve stability.For accurate measuring temperature, the text adopted pt100 as the temperature sensor and used four lines of the resistance to reduce error. The temperature range of pt100 is from 50 to 400℃, which correspond from 119.4～247.04ohm in sequence. Ago analog signals of pt100 converted to digital signal, Lm317 and lm337 constitutes a current source of 10mA, which filtered directly connects to the ad of the aduc845. Aduc845 has the ad converter of 24 bit, to simplify the circuit, improve the accuracy and reduce costs.This text improves the buck converter, increases the buffer circuit and solves diode's the problem.of reverse restore. Also,hardware circuit includes the drive and protection circuit of the over current and overvoltage of exb841, the circuit which detect temperature, the power circuit and the circuit of man-machine interface, with the constant temperature system with a PID controller.This text selects the C/C++ high-level language, that is compiled and debugged in Keil c7 environment. In designing software and hardware process, all kinds of improvements and tests and the combination debug with the software and hardware are done, so the functionality and precision is a larger increase.At last, I summarize the whole text, illustrate the shortage and look forward to prospects and future of the temperature calibrator.