Microwave based flow detector
How does a Microwave based flow detector work?
A microwave-based motion detector detects the Doppler shift of the flowing material. A complete flow detector consists of a transmitter and transducer.
The transducer has a Gunn diode configured within a waveguide (horn) antenna and functions as both a microwave transmitter and receiver. The transmitter contains the measuring electronics and relay output. The Gunn diode emits a low power, continuous signal that is reflected from moving material in the process. It monitors the movement of bulk materials and can be used to detect and indicate material blockages or feeder shutdowns.
If the reflecting medium is moving, there will be, in accordance with the Doppler effect, a frequency shift between the transmitted and the received signals. The frequency shift is proportional to the velocity of the process material. The transducer superimposes the transmitted and received signals. Since the two frequencies differ only slightly, the differential signal produced is low frequency. This low frequency signal is delivered to the electronics by capacitive coupling and processed in a low frequency amplifier.