In order to ensure the measuring accuracy of resistance type sensor,a gas detecting system based on constant current circuit has been designed. The system uses constant current to make the gas sensor's resistance linear with output voltage,so that the detecting resistance accuracy of gas sensor is improved. The constant current circuit consists of reference voltage supply, current negative feedback circuit, voltage stabilizing diode, and load resistance. After calibration,its measuring range is 0~l 000 kΩ,and corresponding average measuring error is less than 0. 0272%. By using SnO2 sensor to detect 0~2 053. 57 mg/m3 ethanol gas, the calibration results show that the resistance decreases exponentially as the concentration increases , and the maximum detection error is less than +1, 5%.%为保证电阻式气敏元件的高精度检测,设计了一种基于恒流源的气体浓度检测系统.该系统利用恒电流源,使传感元件电阻与电压变化呈线性关系,以提高气敏元件阻值随气体浓度变化的准确度.恒电流源包括基准稳压电源、电流负反馈电路、稳压二极管和待测气敏元件.经过参数整定,其测电阻范围可达0～1 000 kΩ,平均测量误差小于0.027 2％.利用SnO2传感器检测浓度为0～2 053.57 mg/m3的乙醇气体,测量出传感器电阻随浓度增加呈e指数下降趋势,系统最大测量误差小于±1.5％.
展开▼
