P, I Electronic Controllers

1. ICE401: PROCESS INSTRUMENTATION
AND CONTROL
Class 24
Proportional, Integral Electronic Controllers
Dr. S. Meenatchisundaram
Email: meenasundar@gmail.com
Process Instrumentation and Control (ICE 401)
Dr. S.Meenatchisundaram, MIT, Manipal, Aug – Nov 2015

2. Single Mode:
Process Instrumentation and Control (ICE 401)
Dr. S.Meenatchisundaram, MIT, Manipal, Aug – Nov 2015
Try:
• Level measurement in a sump tank is provided by a transducer
scaled as 0.2 V/m. A pump is to be turned on by application of +5V
when the sump level exceeds 2.0 m. The pump is to be turned back
off when the sump level drops to 1.5 m. Develop a two-position
controller.
Solution:
• Let us use the circuit of shown before. The high and low trip
voltages will be determined by the conditions of the problem. From
these, the values of the resistances can be determined.
VH = (0.2 V / m)(2.0 m) = 0.4 V
VL = (0.2 V / m)(1.5 m) = 0.3 V

3. Single Mode:
Process Instrumentation and Control (ICE 401)
Dr. S.Meenatchisundaram, MIT, Manipal, Aug – Nov 2015
• This gives the following relations for the resistances and VSP:
0.4V = Vsp
0.3V = Vsp – (R1/R2)V0
• For, Vsp = 0.3 V
R1/R2=0.02
Since there are two unknowns and only one condition, one unknown
can be selected. Picking R1=5k for example, means that R2= 250k .

4. Proportional Control Mode:
Process Instrumentation and Control (ICE 401)
Dr. S.Meenatchisundaram, MIT, Manipal, Aug – Nov 2015
0p pp K e p= +
0out p pV G e V= +
where,
Gp = R2/R1

5. Proportional Control Mode:
Process Instrumentation and Control (ICE 401)
Dr. S.Meenatchisundaram, MIT, Manipal, Aug – Nov 2015
Try:
A temperature controller controls temperature from 100°to 200°C. A
sensor provides an output of 2 to 8 V for this temperature range. The
controller output drives a heater with an output of 0 to 5 volts. What
circuit gain is needed if the controller is to be used with a proportional
gain of 4%/%?

6. Integral Control Mode:
Process Instrumentation and Control (ICE 401)
Dr. S.Meenatchisundaram, MIT, Manipal, Aug – Nov 2015
0
( ) (0)
t
I pp t K e dt p= +∫
0
(0)
t
out I e outV G V dt V= +∫

7. References:
• Process Control Instrumentation Technology, by Curtis D.
Johnson, Eighth Edition, Pearson Education Limited.
Process Instrumentation and Control (ICE 401)
Dr. S.Meenatchisundaram, MIT, Manipal, Aug – Nov 2015