FORCE BALANCE PRINCIPLE:
“A controller which generates and output signal by opposing torques”.
The input force is applied on the input bellows which novas the beam. This crackles nozzle back pressure. The nozzle back pressure is sensed by the balancing bellows which brings the beam to balance. The baffle movement is very less about 0.002” for full scale output.
MOTION BALANCE PRINCIPLE:
“A controller which generates an output signal by motion of its parts”.
The increase in input signal will cause the baffle to move towards the nozzle. The nozzle back pressure will increase. This increase in back pressure acting on the balancing bellows, will expands the bellows, there by moving the nozzle upward. The nozzle will move until motion (almost) equals the input (baffle) motion.
Advantages of force Balance:
- Moving parts are fever.
- Baffle movement is negligible.
- Frictional losses are less.