Impedance analyzers are a class of instruments which measure complex
electrical impedance as a function of frequency. This involves the phase sensitive measurement of current and
voltage applied to a device under test while the measurement frequency is varied over the course of the measurement. Key specifications of an impedance analyzer are the frequency range, impedance range, absolute impedance accuracy and phase angle accuracy. Further specifications include the ability to apply voltage bias and current bias while measuring, and the measurement speed. Impedance analyzers typically offer highly accurate impedance measurements, e.g. with a basic accuracy of up to 0.05%, and a frequency measurement range from μHz to GHz. Impedance values can range over many decades from μΩ to TΩ, whereas the phase angle accuracy is in the range of 10 millidegree. Measured impedance values include absolute impedance, the real and imaginary part of the measured impedance and the phase between the voltage and current. Model-derived impedance parameters such as conductance, inductance and capacitance are calculated based on a replacement circuit model and subsequently displayed.
LCR meters also provide impedance measurement functionality, typically with similar accuracy but lower frequency range. The measurement frequency of LCR meters is generally fixed rather than swept, and cannot be displayed graphically. A fourth implementation, the
vector network analyzer (VNA), can be considered a distinct instrument. In contrast to impedance analyzers, VNAs also measure impedance but usually at much higher frequencies and with much lower accuracy compared to impedance analyzers. == Reactance chart ==