基于方波恒流源细胞电阻测量系统的设计实现

Design and implementation of cell resistance measurement system based on square wave constant current source

设计实现了一个细胞电阻测量系统。该系统基于方波恒流源电路，将交流方波微电流信号施加在被测细胞或细胞群上，根据欧姆定律，输出与被测细胞电阻成正比的交流方波电压，再经滤波、整流、A／D转换后获得电阻数字显示值。系统中恒流源的应用有效消除了测量电极电解作用及细胞膜电位对测量结果的影响，方波电压的产生则便于进一步滤除直流干扰成分，提高测量准确度。利用生理盐水模拟细胞液进行实验，可以观察到随着测试表笔距离的加大，测量电阻也在做正比例增加，结果受表笔电极化影响很小，且在有效测量范围0～1000Ω内，测量均方误差小于6％，能够基本满足临床上离体辅助检测的需求。

A cell resistance measurement system based on a constant current source is designed .In the system ,AC square w ave micro‐current signal is first being applied to the cells or the cell mass ,and then an output square‐w ave volt‐age proportional to the measuring cell resistance is obtained according to Ohm＇s law .Finally digital display values can be attained after rectification and A/D conversion .The application of constant current source can effectively improve meas‐urement accuracy by eliminating the effect on the measuring results of the cell membrane potential and measuring elec‐trode electrolysis .And also ,as using square wave ,the DC influence can be easily filtered by the system with simple cir‐cuit .Finally ,using saline to simulate experimental cell fluid ,the experiment shows that with the increasing distance of test probes ,the measured resistance is increased in direct proportion and the results have little effect on polarization and effective .In addition , results demonstrate that the mean square error is less than 6% in the measurement range 0 -1 000 Ω and it can basically meet to the needs of isolated assisted detection in clinically .