# Impedance Measurement

Measure impedance of circuit as function of frequency

**Libraries:**

Simscape /
Electrical /
Specialized Power Systems /
Sensors and Measurements

## Description

The Impedance Measurement block measures the impedance between two nodes of a linear circuit as a function of the frequency. It consists of a current source Iz, connected between inputs one and two of the Impedance Measurement blocks, and a voltage measurement Vz, connected across the terminals of the current source. The network impedance is calculated as the transfer function H(s) from the current input to the voltage output of the state-space model.

$$H(s)=\frac{{V}_{z}(s)}{{I}_{z}(s)}.$$

The impedance (magnitude and phase) as function of frequency is displayed by using the Impedance versus Frequency Measurement tool of the Powergui block.

The measurement takes into account the initial states of the Breaker and Ideal Switch blocks. It also allows impedance measurements with Distributed Parameters Line blocks in your circuit.

The source impedances are taken into account in the impedance calculations. By definition, the impedance of voltage sources is 0 (voltage source blocks are considered as short-circuit) and the impedance of current sources is infinite (current source blocks are considered as open-circuit).

In some applications, you may need to delete current or voltage source blocks manually in order to ignore their impact on impedance calculations.

### Assumptions and Limitations

The only nonlinear blocks that are taken into account during the impedance measurement are the Breaker, Three-Phase Breaker, Three-Phase Fault, Ideal Switch, and Distributed Parameters Line blocks. All other nonlinear blocks, such as machines and power electronic devices, are not considered, and they are disconnected during the measurement.

If you plan to connect the Impedance Measurement block in series with an inductance, a current source, or any nonlinear element, you must add a large resistor across the terminals of the block, because the Impedance Measurement block is simulated as a current source block.

## Ports

### Conserving

## Parameters

## Extended Capabilities

## Version History

**Introduced before R2006a**