Michell online hygrometer

The Michell online hygrometer provides ultrahigh-pressure (UHP) air as a specialised form of compressed air. Rather than being compressed to the standard 7 bar(g), UHP air is often supplied at 450 bar(g), which makes drying the air a critical consideration — both for energy savings and for safety. Given the high pressures, even a small amount of water vapour would condense at ambient temperatures.

The online hygrometer supplies air at high pressure, making it a good source of power. Because of the extra force it provides, it is often used in marine and military applications such as clearing submarine ballast tanks for ascent to the surface. The high pressure of the air allows the tanks to be cleared quickly and gives the crew a greater level of control and responsiveness.

Due to the cold temperatures below sea, as well as the cooling effect of reducing the pressure of gas, it is vitally important to avoid excess moisture in the UHP air. If ice formed it could block or damage the equipment and completely disable the submarine.

The online hygrometer measures the water dewpoint at delivery, as part of the company’s portable test set. The ceramic impedance sensor is able to measure the dewpoint temperature at line pressure.