方波激励的生物电阻抗谱自动测试系统

An automatic test system of electric bio-impedance spectrum based on square wave excitation

目的为解决多频率方波自动测量生物电阻抗谱的问题,本文设计了一个方波激励的生物电阻抗谱自动测试系统。方法将任意波形函数发生器、仪表放大器和采集卡以及PC组成电阻抗谱自动测试系统,利用PC中的Labview程序分别控制函数发生器和采集卡自动完成激励的产生和数据采集,并将采集到的数据自动保存在PC中,最后利用Matlab程序对数据进行快速傅里叶变换得到阻抗谱。首先对阻抗网络模型进行阻抗谱的仿真,将仿真得到的阻抗谱和理论计算得到的阻抗谱对比;再分别使用此系统和阻抗分析仪对阻抗网络模型进行阻抗测量,将测试得到的阻抗谱进行曲线拟合得到元件值,根据元件值比较测试误差。最后,使用方波激励和稳态正弦激励对酵母细胞悬浮液进行阻抗测量,根据酵母细胞悬浮液的阻抗谱计算介电谱,将得到的介电谱和参考文献中的介电谱作比较,并比较两种激励的测量时间。结果仿真得到的阻抗谱和理论计算得到的阻抗谱一致,验证了方波激励的可行性。测试系统对阻抗网络模型的测试结果和阻抗分析仪的相比误差小于10%,验证了测试系统的正确性。使用方波激励和稳态正弦激励测试酵母细胞悬浮液的阻抗谱,转换成介电谱后,发现其变化规律和参考文献所得结果相符。在100Hz^2MHz的测试范围内,方波激励的测量时间为0.9s,稳态正弦激励的测试时间为1.7s,方波激励的测试速度快。结论本文设计的方波激励的生物电阻抗谱自动测试系统具有自动测试生物阻抗谱的能力,由于使用方波激励,可以兼顾速度和信噪比的要求,实现了计算机控制,可根据实际情况调整激励信号的参数,具有很强的灵活性和可扩展性。

Objective To solve the problem of automatic measurement of bio-impedance by multi-frequency square wave. Therefore,an automatic test system of electric bio-impedance spectrum based on square wave excitation was designed in this paper. Methods The automatic test system was composed of the function generator,the instrumentation amplifier and the acquisition card and PC. The Labview program in PC was used to control the function generator and the acquisition card to generate square wave excitation and data acquisition respectively. The collected data was automatically saved in PC. The impedance spectrum was obtained by Fast Fourier Transform of the data by using Matlab program. Firstly,the impedance spectrum of the impedance network model are simulated,and the simulated impedance spectrum are compared with the theoretical impedance spectrum. Then the impedance spectrum of the impedance network model was measured by the system and the impedance analyzer respectively,and the measured impedance spectrums were curve-fitted to obtain the component values,and the test errors were compared according to the component values. Finally,the impedance spectrums of yeast cell suspensions were measured by using square wave excitation and steady-state sinusoidal excitation. The impedance spectrums of yeast cell suspensions were analyzed to obtain dielectric spectroscopies. The measured dielectric spectroscopies were compared with those in literature,and the measurement times of two kinds of excitation were compared. Results The simulated impedance spectrum was consistent with the theoretical impedance spectrum,which verifies the feasibility of square wave excitation. The error of impedance network model measured by square wave excitation was less than 10% compared with that of impedance analyzer,which verifies the correctness of the test system. The impedance spectrums of yeast cell suspensions were measured by square wave excitation and steady-state sinusoidal excitation,and then converted into dielectric spectrums. The results were in agreement with those obtained in references. In the test frequency range of 100 Hz-2 MHz,the measurement time of square wave excitation was 1.7 s,and that of steady-state sinusoidal frequency excitation was 0.9 s,the automatic test system of electric bio-impedance spectrum based on square wave excitation can test faster. Conclusions The automatic test system of electric bio-impedance spectrum based on square wave excitation in this paper has the ability to automatically measure bio- impedance. Due to the use of square wave excitation,both speed and signal- to-noise ratio could be considered. It realized computer control and could adjust the parameters of excitation signals according to the actual situation,so it has strong flexibility and expansibility.