Analysis of a constant voltage anemometer circuit

A new circuit arrangement using an operational amplifier that maintains a constant voltage across a sensor connected between a node in the circuit and ground is described. The basic circuit consists of a T resistor network in the feedback of an operational amplifier where the sensor is connected in place of the center grounded element. The analysis of such a circuit arrangement is presented for a particular application to a hot-wire/film anemometer. An introduction is given to focus on the requirements of such a circuit to function as an anemometer, considering the hot-wire as a first order low-pass filter due to its thermal inertia. An innovative internal compensation method for the thermal inertia effects is presented which would extend the bandwidth. The expression for the overall bandwidth of such a circuit is derived with its sensitivity. An approach to extend the bandwidth even further using a composite amplifier configuration is presented. Experimental results showing excellent agreement with conventional approaches are presented. The advantage of the constant voltage operation in terms of insignificant cable capacitance effects and higher signal to noise ratio is discussed