Gas-solid two-phase flow measurement technique based on capacitance sensors is considered to be the most promising gas-solid flow measurement technique.The capacitance sensor interface circuit is the key of capacitance sensor,and is important to the development and application of capacitive method gas-solid flow measurement technology.Tiny capacitance measurement' s difficulty lies in the presence of stray capacitance and electromagnetic interference,and relaxation oscillator circuit can eliminate both ends of the capacitance' stray capacitance through the differential structure,it increases stability of circuit operation.Circuit can turn capacitance value into pulse width only with high and low level by the way of oscillation in order to transmit measurement result without interference.The reasonable use of the microprocessor can achieve high-precision measurement of the pulse width,thereby increasing the sensitivity and resolution of the measuring circuit as a whole.In order to be applied to the flow concentration measurement of gas-solid flow,the relaxation oscillator circuit with a reference capacitance was applied and its performance was tested.The results show that hysteresis error of the relaxation oscillation interface circuit with reference capacitance is 0.30％,nonlinearity error is 0.30％ and repeatability error is 0.32％,and it is suitable for flow concentration measurement of gas-solid flow.%基于电容传感器的气固两相流测量技术被认为是最有前途的气固流测量技术,而电容传感器接口电路是电容传感器乃至电容法气固两相流测量技术研发和应用的关键.微小电容测量的难点在于杂散电容的存在以及电磁干扰,而张弛振荡电路可以通过差动结构消除待测电容两端的杂散电容,电路工作稳定性较高,电路还可以将电容值通过振荡的方式转化为只有高低电平的脉冲宽度,便于不受干扰的传输测量结果,同时使用合理的微处理器可实现对脉宽的高精度测量,从而提高测量电路整体的灵敏性与分辨力.为了应用于气固流相浓度测量,使用带参比电容的张弛振荡电路,并进行了性能测试.结果表明,带参比电容的张弛振荡接口电路迟滞误差为0.30％,非线性误差为0.30％,重复性误差为0.32％,可以在气固两相流相浓度测量中应用.
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