I'm trying to develop a system for bioimpedance measurement with the IC **AD5933**.

*The AD5933 is a high precision impedance converter system that combines a frequency generator with a 12-bit, 1 MSPS, Analog-to-Digital converter. The frequency generator allows an external complex impedance to be excited with a known frequency. The signal in response from the impedance is sampled by the on -board ADC and a discrete Fourier transform (DFT) is done by an on-board DSP engine.*

The DFT algorithm returns both a real (R) and imaginary (I) data-word at each frequency point along the sweep. The impedance magnitude and phase are easily calculated using equations.

To convert this number into impedance, it must be multiplied by a scaling factor called the **gain factor**. The gain factor is calculated during the calibration of the system with a known impedance connected between the VOUT and VIN pins.

The measured **impedance** at the frequency point is given by:

*My problem is that I need to use only the real (Resistance) and imaginary (Reactance) information, rather than the Impedance Magnitude.*

Because the equations of body composition require, for example:

*So, my question is:*

*How do I apply the gain factor only in real (Resistance) and imaginary (Reactance) values?*

Tks!

## Best Answer

Sorry, but I didn't understand.

For example, in the Datasheet of the AD5933 there is the following example:

Gain Factor = 515,819 x 10 ^ (-12)Real data register = -1473Imaginary data register = 3507So, the

is:Magnitude of the impedance3802,863Then, applying the

, thegain factoris:correct Magnitude of the impedance509,791 k.

My point is:If I just multiply the values of the registers

and-1473with the3507(515,819 x 10 ^ (-12)), and calculate thegain factor:correct Magnitude of the ImpedanceI can't get the correct impedance value, which was previously calculated

.509,791 k