All machines with lubrication oil systems benefit from a measurement of moisture content in the oil. Vaisala HUMICAP^® instruments monitor the water activity of the oil, which directly indicates the margin to free water formation in the oil. The measurement is different from the traditional ppm moisture measurement because it is independent of oil type, age and temperature.Vaisala oil moisture measurement probes are installed through a ball valve and can be inserted and removed while the process is running and under pressure. The measurement points are typically placed before critical bearings and other parts of the machine, and/or in the oil tank. A hand-held meter is available for spot-checking and calibration of fixed instruments.