Impedance analyzers usually apply a set voltage amplitude to the item of interest and measure the current and corresponding phase angle.

Electrode contact impedance may be significant in bio-impedance measurements therfore, better to use current excitation to maintain constant probing current.

It depends on the measurement setup you use. If you are considering building a frequency-response analyzer (FRA) setup to measure impedance, I encourage you to use current source (CS) excitation. CS impedance based measurements lead to an open-loop impedance identification problem while voltage source based (VS) lead to a closed-loop impedance identification problem. You can find all the details in http://iopscience.iop.org/0967-3334/34/10/1217

Hubert de Bruin McMaster University

I would choose a constant current source to avoid electrode impedance effects, whether using a two electrode or four electrode setup. This is the most common approach in bioimpedance measurements, although I am not sure which approach is common in bioimpedance imaging systems.

That is better using constant current to measure the bio-impedance, especially for the humans. Because the safe current should be lower than mA lever for the measurement of the humans.

There is no unique answer to this question. Some factors to consider:

- In-vivo vs. in-vitro measurements: In-vivo measurements are limited by the maximal acceptable auxiliary current through the patient according to accepted standards. In-vitro measurements are limited by non-linear phenomena in electrodes because of excessive current density.

- Value of the electrical impedance to be measured: Current injection is limited by voltage compliance of the electronic circuits hence maximal acceptable currents for large impedances can be very small and any leakage current because of stray capacitance to the environment becomes very important.

- Frequency range: parasitic capacitances in electronic circuits make it very difficult to achieve an “ideal” current source through the sample under test.

- In-house expertise: good voltage sources are readily available whereas designing a good current source takes some expertise in analog circuit design at the system-on-board level. If you apply a constant voltage and measure the current through the sample, you avoid the design of current sources.

I do agree with B Murat , moreover the current should be passed with a constant frequency depending upon that which part of the body is taken into consideration.

you can use the voltage controlled current source for the bioimpedance measurement. There is a paper about it:

https://www.researchgate.net/publication/261379649_A_high_accuracy_voltage_controlled_current_source_for_handheld_bioimpedance_measurement?ev=prf_pub

Conference Paper A high accuracy voltage controlled current source for handhe...

Absolutely: current excitation by an electronic current generator (frequency range about 2 MHz)

Current excitation is the common way to measure bio-impedance, but you need to modulate this current with high frequency signal at least 500 KHz (sinusoidal is better) to prevent the current hazards on the human body.

You could consider the following paper by Y. Mohamadou et al.: Performance evaluation of wideband bio-impedance spectroscopy using constant voltage source and constant current source, Meas. Sci. Technol. 23 (2012), doi:10.1088/0957-0233/23/10/105703

And this one too

http://iopscience.iop.org/0957-0233/25/1/015501