Temperature Monitor System With Mult-Way And High Accuracy

This subject involves a high-precision and wide-range application system on intelligent temperature measurement with many measuring points. It uses thermal resistance Pt100 with better performance evaluation as temperature sensor and constant current source circuit to obtain signal .The first-step amplification of the regulated circuit adopts special-purpose high- performance amplifier AD620,and the back one adopts program-controlled biased voltage designed by myself to raise resolution ratio of measure. It uses 12-bit A/D converter TLC2543 with serial interface to convert signal and the CPU adopts low-price at present but skilled AT89S51. HD7279 with simple interface but powerful function appears as display or drive chip. At the same time this system also involves communication interface circuit of RS485 bus and offers the open agreement. Finally, the power source of the system is designed by using the latest single chip of switch power. To correct the error of circuit resistance brought by 2-line, the outer line of Pt100 adopts 4-line ways. To reduce the hardware cost, multiple analog switches are used to change over 8-way temperature difference signal. For improving systematic anti-interference performance, the measuring of temperature adopts digit filter algorithm. And for raising precision and reducing memory space, table look-at and different-value methods are used in software. This article gives overall theory analysis around the factors of producing error, and demarcates the system by using standard resistance box. The experiment proves that this design has totally reached the request booked. Multiple temperature system formed by this subject has suchcharacters as simple structure ,low price, high measuring precision, wide range, etc. It has certain practicality and higher society popularized value.