The piezo breeze sensor is a basic but unique piezo sensor application in which changes in the velocity of subject gases can be quickly and accurately determined.
To accomplish this, the breeze sensor is comprised of two piezoelectric elements in a series-opposed circuit (see Figure 1).
One element is exposed to the gas whose velocity is being monitored, the other is isolated from the gas. When the gas is motionless, or its flow is relatively constant, charged air molecules at the surfaces of the element exposed to the gas are in balance with the free charge carriers and dipoles in the element.
The charge across the element is balanced and both elements generate the same electric charge. Voltage across the bias resistor is approximately zero. When gas movement increases, however, the charges at the surfaces of the element exposed to the gas are removed from the surface at an increased rate, and the charge across the element is thrown out of balance. A voltage across the resistor indicates the two elements are no longer in balance (see Figure 2). APC’s engineers recommend using APC-850 piezo material as a starting point for developing most piezo sensors.
