Impedimetric sensors

Impedimetric sensor technology (fig. 1) is based on TiN interdigital capacitors (yellow) on a silicon substrate (grey) with field oxide passivation (green). A PECVD nitride layer (white) passivates the electrodes and constitutes the recognition system for the actual measuring task. The overall impedance of the stray field capacity shows a marked frequency response, which is greatly dependent in its course on the properties of the surrounding medium (fig. 2).

For example, a significant difference is measurable between a dry and moist sensor surface. This enables the use of the measuring principle as a moisture sensor (see capacitor sensors).

In combination with a control circuit the principle can be used to carry out a dewpoint measurement (see dewpoint measuring devices).