Reduction of power consumption and expansion of the measurement range by pulsed excitation of thermal flow sensors

- A pulsed excitation method for thermal flow sensors is presented.
- Driving the heater of a thermal flow sensor with a voltage pulse will reduce power consumption dramatically.
- Generating impulses of constant energy by discharging a capacitor to drive the heater of a thermal flow sensor will compensate thermal influences.
- The response of a constant energy pulse provides more information than a continuous thermal voltage and allows to expand the measurement range.

A new excitation method for thermal flow sensors has been developed by powering them not continuously, but with short pulses. The impulses can be generated by a pulse generator or a capacitor circuit and can have a duration of milliseconds or less, depending on the voltage and the required resolution. Although the sensor will not reach the thermal equilibrium which is typically used for flow measurements, the dynamic heating response curve of the impulses contains enough information to determine the flow rate.