Example measurements

This page shows examples of high series impedance measurements.

Mesh

The figure below shows an example of a mesh. An ideal mesh has a constant, frequency independent series impedance. This one has a specific resistance of 520 Rayl.

In this case, the diameter is 2 mm and the mesh is rigid across the whole measurement frequency range. A mesh however can have a resonance. If the mesh is much larger or when it is excited at a higher frequency than 8 kHz, the resonance can become visible.

Membrane

The figure below shows an example of a membrane. A membrane primarily has compliant behavior. This means that the series impedance is inversely proportional to frequency and the phase is -90$°$. This is similar to the reactance of a capacitor:

$$X_C=\frac{1}{i\omega C}$$

Because the µZ works over such a wide frequency range, it captures the following properties:

1. Compliance
2. Leakage: at $f<200$ Hz the magnitude flattens and the phase gradually returns to 0$°$.
3. Resistance: at $f=6$ kHz the membrane resonates and the impedance magnitude has a minimum. The value of the minimum is related to the resistance.
4. Mass: beyond the resonance, the impedance is proportional to frequency and the phase is +90$°$. This is similar to the impedance of an electric inductor:

$$X_L=i\omega L$$