Forum Post: ADS1299 current source for impedance measurement

Hi,

I have a question about ADS1299 internal current souces for impedance measurement. I'm using internal current source with amplitude of 6nA and frequency of Fdr/4. This current can be modeled as:

I=6nA * sin(2*pi*(Fdr/4)*t + phase)

I need phase of the current signal so I can measure real electrode-skin impedance's which are complex (resistive-capacitive modeled). Does anybody know or measured phase angle of this current source? Also does the all current sources have the same phase angle which is independent of the IC's?

Regards,

Vojin Ilic