Pyromation Series 610 1_16 DIN - Manual (Page 123)

1 /
4
-DIN, 1 /
8
-DIN & 1 /
16
- DIN Controllers & Indicators - Product Manual
12 Manually Tuning Controllers
Single Control Tuning (PID with Primary Output only)
This simple technique balances the need to reach setpoint quickly, with the wish to limit
setpoint overshoot at start-up or during process changes. It determines values for the
Primary Proportional Band (
):) ), Integral Time Constant ( +-/ ) and
( * /! ) that allow the algorithm to give acceptable results in most
applications that use a device.
1. Check that the Setpoint Upper Limit ( -)1' ) and Setpoint Lower Limit ( -)'' ) are set to
safe levels for your process. Adjust if required.
2.
3. Select On-Off control (i.e. set ):) = 0).
4. Switch on the process. The will oscillate about the setpoint. Record the
Peak-to-Peak variation (P) of the first cycle (i.e. the difference between the highest value
of the first overshoot and the lowest value of the first undershoot), and the time period of
the oscillation (T) in minutes. See the example diagram below - Manually Tuning PID.
Derivative Time
Constant PID control
single control
CAUTION:
This technique is suitable only for processes that are not harmed by large
fluctuations in the process variable.
Set the Setpoint to the normal operating value for the process (or to a lower value if
overshoots beyond this value might cause damage).
process variable
5. Calculate the PID control parameters using the formula below. Input Span is the difference
between Scale Range Lower Limit and Scale Range Upper Limit:
Input Span
P
):) = x 100
+-/ = T minutes
6
T
+ .! = minutes
Time
Process Va
riable
Figure 39. Manually Tuning PID
Page 118
Manual Tuning 59305, Issue 6 – March 2006