I am trying to measure a microfluidic circuit, a conduction circuit which can be modeled down to a CRC circuit using the AD5933 Evaluation Board. Page 8 of the Data Sheet ,the AN- 1252 states that:

MEASURING A COMPLEX IMPEDANCE

To measure complex impedance, refer to the conversion table (see Table 7) to calculate the maximum and minimum impedance based on the excitation frequency. This section describes three points to keep in mind.

Do Not Calibrate the System with a Complex Impedance

Otherwise, phase results will be not as expected. This is explained in the Calculating the Gain Factor section.

**Questions:**

- Table 7 gives schematics of such complex impedance examples, however could you confirm if my microfluidic CRC circuit is considered to be complex impedance?
- The warning states "Do Not Calibrate the System with a Complex Impedance" and given the fact that correct measurements require accurate calibration, could you shed some light on the accuracy range I will expect on the CRC circuit and confirm if the AD5933 is a suitable tool to measure the impedance of the conduction cell?

Thank you for your time.

Raymond

Hi Raymond:

The "table 7" of AN-1252 showed several typical complex impedance circuit calculation, for your measurement what the results are expected?

The accuracy of your system is depend on the ∂Z/∂C and ∂Z/∂R in your model, for the AD5933 accuracy please check: http://www.analog.com/media/en/technical-documentation/data-sheets/AD5933.pdf

There have a circuit note about the AD5933 conductivity application, please check: http://www.analog.com/en/design-center/reference-designs/hardware-reference-design/circuits-from-the-lab/CN0349.html