Micromod Micro-DCI: 53SL5100A Single Loop Controller - Manual (Page 110)

Single Loop Process Controller Instruction Manual
102 Instrument Tuning
Table 10-4. Step Response Method
Step Procedure
1 Set the process to approximately normal conditions in Manual mode.
2 Introduce a 10% (approximate) step change to the manually regulated signal to the
valve. Observe the magnitude of the step in percent of full signal span F. Also plot a
graph of the resulting transient curve traced by the controlled variable.
3 Draw a straight line tangent to a point on the curve having the greatest slope (most
linear).
4 Measure the apparent dead time L in minutes as shown in Figure 10-1 .
5 Measure RL, the product of the slope and dead time as shown in Figure 10-1 . This
value should be expressed in percent of full scale span.
6 Compute the best settings as follows:
A. Proportional (P): P.B. = (100 RL)/ F.
B. Proportional & Integral(PI): P.B. = (100 RL)/ F, TR = 3L
C. Proportional, Integral, and Derivative (PID): P.B. = (80 RL)/ F, TR = 2L, TD = 0.5L
Figure 10-1. Typical Step Response Method