BioImpedance Analysis

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Precision and Accuracy of Impedance Measurements

Currently available impedance machines require calibration using resistors or resistor-capacitor (RC) circuits of pricisely known component values. Assuming correct calibration, like most solid-state electronic devices, impedances machines are capable of making measurements with a high degree of precision and accuracy. There is, however, precious little published information independent of manufacturers' specification claims.

Typical quoted values are as follows: 0.5 - 3 <0.5
Parameter Range Resolution* Accuracy* (%)
Impedance (Ohms) 0 - 2000 0.5 - 2 0.5 - 3
Resistance (Ohms) 0 - 2000 0.5 - 2
Phase (ø) -5 - 50 0.1 - 0.5
Frequency (kHz) 1 - 1350 0.2 - 1 <0.5
*Depends upon frequency of measurement.

Electronic accuracy is generally high (see above) although differences between different manufacturers' analysers or, indeed between different machines from the same manufacturer, of up to 10% have been noted. The causes of such differences are unknown but may result from inadequate calibration rather than electronic instability.