Abstract: A sensor for measuring changes in mass air flow is described that uses one or more thermoelectric devices, each of which serves both as a heating element and as a differential temperature sensor. The thermoelectric device or devices are sandwiched between two surface plates. The sensor operates the device or devices in constant current or in pulsed current mode. The operation in constant current mode involves passing the current through one thermoelectric device to create a temperature differential between the two surfaces. A second thermoelectric device generates a voltage in response to the differential, the voltage being proportional to the air flow rate. In another embodiment, the device contains a single thermoelectric device that operates in a pulsed mode, first to create a temperature differential using an applied current, and then to measure the voltage. When the voltage reaches zero, the cycle is repeated. The cycle time determines the air flow rate.