How to measure the dew point in the air separation system?

Dew point meter is required to measure the dew point of compressed air. There are two common instruments for measuring the dew point of compressed air. Their respective characteristics are as follows:

1. Mirror dew point meter
The principle of the dew point meter is to cool the measured gas to a certain temperature by refrigeration, so that the water vapor in it can condense onto the mirror surface, and then the temperature at which condensation occurs can be measured based on optical principles.
Theoretically, this method can measure any dew point value as long as all refrigeration temperatures can be achieved. However, the limitation is that the measured gas must be pure enough without any impurities and pollution, otherwise it will cause measurement errors; in addition, due to the use of refrigeration, the working principle is relatively complicated, and each measurement takes a certain amount of time, so it is not suitable for field testing and is mostly used in laboratories.

2. Capacitance/resistance dew point meter
This dew point instrument is characterized by its small size, easy to carry, and large measuring range. Its sensor is usually an aluminum oxide sensor, which can measure the dew point as low as -100°C. The limitation of this type of instrument is that it can only measure the dew point temperature at normal pressure. In addition, the dew point sensor will produce negative offset during long-term use, so it needs to be calibrated.

Different testing methods are suitable for different application scenarios. You can choose according to your actual needs.