3.2.1 - Instrumentation - Measurement
3.2.1 - Instrumentation - Measurement
3.2.1 - Instrumentation - Measurement
3 basic
components
Decision -
of Process Control Controller
Action
Unit 1: Process Control Loop
Pressure
Flow
Level
Process Temperature
pH
dP cell
Capacitance
I/P
Sensor Radar, Sonic
Magnetic
Resistance
IR/Laser
4-20 mA
Transmitter 1-5 Vdc
Controller PID
Fuzzy logic
4-20 mA
Transducer 3-15 psig
Linear
Control valve Equal percentage
20 50
P (psig)
100 20
0 4
0 p(t), psig 200
C (s ) KT
H (s )
PV (s ) T s 1
KT = transmitter gain
T = transmitter time constant
100 20
0 4
0 p(t), psig 200
KT
20 4mA
16mA
0.08mA / psig
200 0psig 200 psig
Or in percent transmitter output (%TO)
KT
100 0%TO 0.5%TO / psig
200 0psig
The signal
• Pneumatic transmitter 3–15 psi.
• electronics -current transmitter 4–20-mA output.
-Voltage transmitter 1-5 volt (VDC)
KT
20 4mA
KT
5 1Volt
200 0psig 200 0 psig
KT
15 3 psi
200 0 psig
Question
Calibration:
A temperature transmitter with a range of 100 to 350oF