TSI offers a wide range of thermal anemometry probes, each specially adapted for a particular application. The broadest probe classifications are based on the fluid measured (liquid or gas) and the number of velocity components. The probe family includes hot film sensors and hot wire sensors. The choice between them is critical for most applications. Hot films consist of a thin film of platinum deposited on a quartz substrate, typically a cylinder attached to the sensor supports. Various cylinder diameters permit different spatial resolutions.