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This example will use EVAL-ADICUP3029 and EVAL_AD5940ELCZ to carry out a 2-wire Impedance measurement.
A standard 2-wire impedance measurement implements a ratio metric measurement. A signal is applied across the known resistor, (RCAL), and the response current is measured. The same signal is then applied across the unknown impedance and response current is measured. A DFT is performed on the response currents to determine the magnitude and phase values of each. The unknown impedance can then be calculated using the following equation:
For more details refer to the application note, AN-1563.
The following is a list of items required to carry out the measurement.
The source code and include files for the project can be found on Git
To compile and run the example open the project in either Keil or IAR. The AD5940ImpedanceStructInit() function is used to configure application parameters. These include setting the value of the RCAL, setting sine wave frequency, configuring the switch matrix and more.
The measurement results are sent to the PC via UART. To establish connection over UART, connect the Micro-USB cable to the PC and to the EVAL-ADICUP3029 board. A terminal program such as RealTerm or Putty is required to display the results
Following is the UART configuration.
Select COM Port Baud rate: 230400 Data: 8 bit Parity: none Stop: 1 bit Flow Control: none
The data on the terminal consists of the Frequency of the excitation signal, the magnitude of the impedance and the phase of the impedance in degrees as in below screenshot.