How does a dew-point sensor work?
Dew point temperature is an important measurement for many industrial processes because it tells operators at what temperature liquid water will condense. In applications such as compressed air used for medical gases, as an example, it’s important the gas is kept dry to avoid liquid water condensing in the pipework to avoid blockages or the growth of mold.
Dew-point transmitters work through impedance. The sensor consists of layers – two electrodes either side of an absorbent layer. As the gas passes over the sensor, the technology absorbs water vapor onto a porous hygroscopic dialectric area between two conductive layers built on top of a base ceramic substrate. Water molecules changes dielectric constant (Ke) of the dialectric which causes a change in impedance of the sensor
Using different materials for the sensors gives dew-point transmitters that provide different characteristics. The most traditional type of sensor uses aluminum oxide for the central absorbent layer. The Avcray Ceramic Metal Oxide moisture sensors are based on new developments in this technology. These sensors are able to measure moisture at pressure and across a wide dew point range from -100 to +20 °C dew point.
Dew Point Measurement in Compressed Air Systems
Compressed air systems in particular require continuous dew point measurement with dew point transmitters. Excessive humidity in the compressed air can result in dangerous corrosion. This causes damage to the system or loss of quality for the end product.
- Moisture in compressed air can lead to faults or failure of pneumatics, solenoid valves and nozzles.
- Moisture has a negative effect on lubrication in compressed air motors. This results in corrosion and increased wear on moving parts.
- In the case of paintwork, humid compressed air causes defects in the end result.
- Freezing moisture can lead to malfunctions in pneumatic control lines.
- Corrosion-related damage to compressed air-operated components may result in system failures.
- In the food and pharmaceutical industry, moisture can have a strong negative impact on the required sterile manufacturing conditions.