Hotwire Systems

“Your ear is the best FFT analyzer.”

Hotwire anemometers are used to measure the flow velocity in gas and in liquids.

Predominantly, they are used to measure unsteady flow effects as they are able to resolve frequencies up to the kilohertz area because of their short response time.

Only a very thin wire – some µm thick – is heated electrically. This wire emits the heat to the environment due to thermal convection and radiation. The flow around the wire is essential for convection if the temperature of the hotwire is significantly above the temperature of the flow.

Using an electrical control circut to heat the wire to a constant temperature (CTA bridges), the voltage required is a direct measure for the speed. The relation between voltage and speed has to be calibrated for each probe.

For industrial use as well as for use in a laboratory we have developed an easy to use 4 channel hotwire system. For tracking down of special phenomina, e.g. for flow separation or for Carman vortex flow the signals of the hotwire can be made audible on a headset.