Measuring the quality of water vapor

Within the project, a device for measuring the quality of superheated water vapor at the outlet of the autoclave was designed. Steam is considered to be of higher quality, if the mass fraction of condensed water drops is smaller.

The device consists of a capacitive bridge, powered by an audio frequency source. Water vapor is introduced into one condenser of the bridge. The relative permittivity of steam increases with the proportion of condensed water, and thus the balance of the bridge is increasingly disturbed. The signal received in one diagonal of the bridge is amplified by an instrumentation amplifier and taken to further processing. The device is simple and robust. The laboratory prototype was realized by our team, and the functional prototype by the customer.

Tests have shown that the device is very sensitive as it can measure relative permittivity changes of 0.001.