Design Of High-precision Platinum Resistance Temperature Measurement System

High-precision temperature measurement is widely used in medical and health,pharmaceutical,food safety and other fields,such as disinfection sterilization,seed tanks,incubators and other closed containers.The thesis designs and implements a set of high-accuracy,low-power temperature acquisition system,including three parts: temperature collector,reading device and host computer software.The temperature collector contains hardware and software parts.In terms of hardware,PT1000 platinum resistor is selected as the temperature sensor,and four-wire constant current source is used to drive the PT1000,thereby effectively reducing the error caused by the wire resistance.AD7794 was selected as the constant current source AD conversion chip.AD7794 is a low-noise,low-power 24-bit high-precision analogto-digital conversion chip,which is widely used in low-power measurement systems.In terms of software,the standard thermometer is used as the benchmark,the least square method is used to fit the data collected by PT1000,the error analysis is carried out by MATLAB to get the optimal fitting method.After testing,the accuracy of the temperature collector has reached 0.01 °C.In low-power design,the ultra-low-power microcontroller MSP430F2274 is used as the main control chip of the collector.The current of the MSP430F2274 is 250 u A in the operation mode and only 0.1u A in the sleep mode.The current of AD7794 is 700 ua in normal working state and 1u A in sleep state.By using the low power design technology,In case of meeting the design requirements,the system can work for 400 hours effectively.The temperature reading device realizes the communication between the collector and the upper computer,and can configure and read 10 temperature sensors at the same time.The upper computer realizes the functions of issuing instructions,reading data,processing data,and generating reports to the temperature collector.Experiments have shown that the temperature measurement accuracy of the highprecision,low-power temperature acquisition system in this paper reaches 0.01 °C,the measurement range reaches-40 °C ? 120 °C,the effective working time reaches 400 hours,which meets the design requirements.It is suitable for sterilization,seed tank,incubator and other instruments and equipment with strict requirements on temperature accuracy and range.