三角波激励ECT测量电路

电容层析成像系统测量电路须有极高灵敏度及动态测量范围。提出一种采用三角波代替传统正弦波作为激励信号的方法,利用C/V转换电路的微分特性,使其输出为方波信号且幅值与被测电容值呈线性关系。瞬态仿真表明,电路的稳定时间缩短为0.65μs;此外,因其不需要相敏解调的环节,电容测量速率大幅提高,将其用于12电极ECT测量,可使测量速度提高到3124帧/s。实测结果表明,该电路的测量灵敏度峰峰值达0.8 V/pF,动态测量范围可达到69 dB。

Triangular-wave Signal Driven Measuring Circuit in ECT

Electrical capacitance tomography measuring circuit requires extremely high sensitivity and dynamic range. The use of triangular-wave signal as excitation signal was proposed to replace the sine-wave signal. Due to the differential characteristics of C/V converter circuit, its output became square wave signal when triangular-wave signal was applied to the measured capacitance. At the same time, the circuit showed good linearity in measuring small capacitance. Transient analysis showed that the settling time was reduced to 0.65μs. In addition, the capacitance acquisition rate could be greatly increased by the removal of phase sensitive detector. For a 12-electrode ECT system, the frame rate could reach up to 3124 frames/s. Experimental results showed that the peak peak value of the measurement sensitivity of the circuit is 0.8 V/pF, and the dynamic range is 69 dB.