ADI AD5933高精度阻抗测量解决方案CN0217

ADI公司的高精度阻抗测量解决方案CN0217采用12位阻抗转换器AD5933/AD5934. AD5933是1MSPS的12位ADC,而AD5934是250KSPS的12位ADC,内部集成了温度传感器(±2°C),系统精度0.5%,工作电压2.7V-5.5V,图1的电路优化了信号链,其阻抗测量范围从低欧姆数到几百kΩ,主要用在电化学分析,生物阻抗分析,复数阻抗分析,生物和汽车传感器,接近式检测,非破坏性检测,以及材料特性分析和燃料/电池状态监视等.本文介绍了AD5933主要特性, 功能方框图, 病毒株血样本测量框图和AD5933评估板主要特性,电路图与材料清单.
The AD5933 and AD5934 are high precision impedance converter system solutions that combine an on-chip programmable frequency generator with a 12-bit, 1 MSPS (AD5933) or 250 kSPS (AD5934) analog-to-digital converter (ADC). The tunable frequency generator allows an external complex impedance to be excited with a known frequency.
The circuit shown in Figure 1 yields accurate impedance measurements extending from the low ohm range to several hundred kΩ and also optimizes the overall accuracy of the AD5933/AD5934.

图1.高精度阻抗测量优化信号链的电路图
The AD5933 is a high precision impedance converter system solution that combines an on-board frequency generator with a 12-bit, 1 MSPS, analog-to-digital converter (ADC). The frequency generator allows an external complex impedance to be excited with a known frequency. The response signal from the impedance is sampled by the on-board ADC and a discrete Fourier transform (DFT) is processed by an on-board DSP engine. The DFT algorithm returns a real (R) and imaginary (I) data-word at each output frequency.
Once calibrated, the magnitude of the impedance and relative phase of the impedance at each frequency point along the sweep is easily calculated. This is done off chip using the real and imaginary register contents, which can be read from the serial I2C interface.
A similar device, also available from Analog Devices, Inc., is the AD5934, a 2.7 V to 5.5 V, 250 kSPS, 12-bit impedance converter, with an internal temperature sensor and is packaged in a 1...