week 2 Flashcards
Need for transmitters
They convert a measured value into a proportional standard instrument signal
Diaphragm
moves a small distance when pressure is applied across it from the process
Force bar
pivots like a see saw when diaphragm moves, pushing flapper closer to nozzle
Flapper/nozzle
flapper restricts air from venting out of nozzle which creates a greater back pressure
Restrictor
smaller hole within the nozzle giving a greater pressure drop when the flapper moves (0.2 to 1.0 bar range)
Value restrictor relay
boost output of air to value signal while keeping output and back pressure at the same pressure
maximum movement of the flapper
10/1000 of an inch
pneumatic transmitters disadvantages
slow response,
lots of moving parts,
high maintenance
pneumatic transmitters advantages
safe in hazardous areas
calibration of pneumatic transmitters
use a test gauge
TX(transmitter) range
0 to 300 mbar
electronic transmitter
diaphragms move the capacitor plates when pressure is applied
electrical transmitter calibration
both input and the output must be measured
advantages of electrical transmitter
fast response,
few moving parts,
disadvantages of electrical transmitter
requires special standard to operate in hazardous areas