The simplest way to determine the presence of water in oil is to use the Visual Crackle test. While this is an effective test for identifying free and emulsified water down to say 500 ppm, its biggest limitation is that the test is nonquantitative and fairly subjective  compact and rugged moisture in oil transmitter suitable for in-line oil monitoring. High accuracy and long-term stability make it ideal for preventive maintenance of plants and machinery. The device accurately measures water activity (aw) and temperature (T) and precisely calculates water content (ppm).