The Droplet Measurement Technologies (DMT) liquid water sensor consists of a heated coil in a protective shroud. An electrical current is passed through the coil which results in the coil heating up. The current through the coil is regulated to maintain it at a steady temperature. During flight, liquid water impacts the coil and causes it to cool off. The system compensates by increasing the current through the coil to maintain the steady temperature. Through a mathematical calculation, the amount of current required to maintain the coil temperature can be related to a liquid water concentration.
The DMT LWC has a particular advantage over the other system onboard designed to measure cloud water (see FSSP) in that it records only liquid water content. The FSSP has a tendency to read small non-spherical ice particles as liquid water (see FSSP). This makes the DMT LWC a more accurate reading in environments with low liquid water concentrations. However, the DMT coil is very sensitive to physical abrasion. Even though the system is outfitted with a shield, the coil element has been broken by large hail on numerous occasions.