一种低功耗高精度的NB-IoT温度采集系统设计

Design of A High-Precision and Low-Power Temperature Acquisition System Based on NB-IoT

针对目前工业应用中对精度和功耗的要求,设计了一款以低功耗、高性能的PIC18F24K22单片机为处理器,以PT100为温度传感器,以高精度的AD7794为A/D转换器,利用NB-IoT通信模块进行无线传输的温度采集系统。设计中PT100采用四线制消除来自连接导线的压降误差,使用精密电阻法为AD7794转换电路提供参考电压,消除了恒流源漂移电流误差,同时减小了参考电压精度对测量结果的影响。设计了高精度的电阻值-温度值的变换关系式,有效地减少了转换误差。测试结果表明,温度的测量精度高于0.04℃,并且在实际的应用环境中具有出色的稳定性。

To satisfy the demand for precision and low-power of industrial applications,this paper presents a wireless temperature acquisition system based on NB-IoT protocol which employs PIC18F24K22 as the processor,PT100 as the temperature sensor as well as AD7794 as the high precision A/D converter. PT100 is connected in a four-wire configuration to eliminate the voltage error from the connection leads and AD7794 uses a precise resistor to acquire a stable reference voltage so as to eliminate the drift of the constant current source and reduce the influence of the precision of the reference voltage. This paper also presents a high-precision resistance-to-temperature conversion equation,which effectively reduces the conversion error. Experimental results show that the precision of measurement is higher than 0.04 degree and the system has an excellent stability in practical environments.