Instruction manual

RFT9739 Field-Mount Transmitter Instruction Manual 87
Appendix
C Theory of Operation
The flow tubes of the Coriolis mass flow sensor are driven to vibrate at
their natural frequency by a magnet and drive coil attached to the apex
of the bent tubes (see
Figure C-1
). An AC drive control amplifier circuit
in the transmitter reinforces the signal from the sensor’s left velocity
pickoff coil to generate the drive coil voltage. The amplitude of this drive
coil voltage is continuously adjusted by the circuit to maintain a constant,
low amplitude of flow tube displacement, minimizing stress to the tube
assembly.
Figure C-1.
Coriolis mass flow sensor