Temperature Automate Test System For Thermocouples And Thermoresistances

Temperature transducers such as thermocouples and thermoresistances play very important roles in industry scene andprocess control. Temperature transducers and digitaltemperature thermometer have been used in manufactory andresearch work widely. So it is concerned if thesethermometers are correct, but the usual equipments of testand measurement are very inefficient, and its connection isvery complex. The temperature control adopts analog PIDcontrol method, so the controller must be adjusted andjudged by manual. These factors bring errors that produceincorrect result.The automatic temperature test system includescomputer techniques, electrical measurement techniques,and automatic control techniques. The system is made up ofthree parts by function. The first part is composed ofmulti-channel scan module,data collector,central controlmodule and communication model, it can scan all channels,convert analog signals to digital signals, and deliver datato the computer; The second part, high stability temperaturecontroller resource is compound of PID control and fuzzycontrol. We have researched the fuzzy control by linearmethod in design; the third part is main program, it can settemperature point according the test rule correctly,monitor control process, when the temperature condition isproper for testing, the main program start scanninginstruction, and processing the data.We adopt TXS2-4.5V low electric potential relay whoseconnect potential is ≤0.3uV in low electric potentialmulti-channel scan equipment design ,the relay is producedby Panasonic corp. Because it often open and close, so thecurrent would fluctuate frequently in circuit, if the groundof control signal of MCU connected with the relay, then thecommon resistance of the ground would bring disturbance ofnoise from the relay, so we adopt photoelectrical insulatingcomponent TLP521 to drive relay. In order to avoid unusefulaction of the relay, we use a chip SN2003 to reverse the phaseof signals at the moment of MCU resetting. In the design,the A/D converter AD7710 is 24 bits IC according Σ-Δchargebalance technique that is produced by AD corp. in UnitedStates, then the measuring accuracy of electricity is 0.02%. The MCU 89C52 contains a usual series bus port that cantransmit data to computer; its baud rate is 2400 bps, itsseries data format is: 1 bit for start, 8 bits for data, 1bit for odd even verified, and 1 bit for stop. Because theI/O voltage of MCU is TTL level, and I/O voltage of computeris 12V,so we use voltage converter IC MAX232CPE that ismulti-channel driver/receiver for RS232, the power supplyis +5V. At the same time, avoiding the disturbance betweenmulti-channels scan equipment and computer, we use two powersupplies of +5V and two pieces of IC 6N136 for insulation.When the multi-channels scan equipment send data, one powersupply (1) of MCU and the input for 6N136(1) is same, anotherpower supply (2) of MAX232CPE and the output for 6N136(1)is same; when the multi-channels scan equipment receive data,one power supply (1) of MCU and the output for 6N136(2) issame, another power supply (2) of MAX232CPE and the inputfor 6N136(2) is same. During the research of high stability temperaturecontroller, we find that two-dimension fuzzy control...