Block diagram of impedance meter. Through a rechargeable battery, a sine-wave alternating current is delivered to the outer two electrodes (a) and (d). A current sensor registers the amount of current delivered to the electrodes. The inner electrodes (b) and (c) are attached to the voltmeter which registers the electrical potential difference between them. The current and voltage readings may be recorded as time series through connections to a computer (BNC outputs).
Ahn et al. BMC Complementary and Alternative Medicine 2005 5:10 doi:10.1186/1472-6882-5-10