K-TEK says its TX thermal dispersion switch can detect trace amounts of water in gearbox oil well before the contamination causes any significant damage. The TX switch produces a millivolt output signal related to the thermal conductivity of the process and temperature differential of the switch. The signal will drop below its normal range (typically 75–77mV) as water contamination increases because water has a thermal conductivity that is different from that of oil. This drop triggers an alarm.