TM 5-3895-374-24-2
955-257
5)
The PB is now very near its "CRITICAL" setting. Carefully increase or decrease the PB setting until cycles or
oscillations JUST appear in the temperature recording.
If no oscillations occur in the process temperature even at the minimum PB setting of 1%, skip steps 6 thru 14 below
and proceed to the Section: "TUNING PROCEDURE WHEN NO OSCILLATIONS ARE OBSERVED".
6)
Read the steady-state deviation, or droop, between setpoint and actual temperature with the "CRITICAL" PB setting
you have achieved. (Because the temperature is cycling a bit, use the average temperature).
7)
Measure the oscillation time, in minutes, between neighboring peaks or valleys.
This is most easily accomplished with a chart recorder: but a measurement can be read at 1 minute intervals to obtain
the timing.
8)
Now, increase the PB setting until the temperature deviation, or droop, increases 65%.
The desired final temperature deviation can be calculated by multiplying the initial temperature deviation achieved with the
"CRITICAL" PB setting by 1.65 or by use of the convenient Nomogram I below. Try several trial-and-error settings of the
PB control until the desired final temperature deviation is achieved.
NOMOGRAM I
9)
You have now completed all the necessary measurements to obtain optimum performance from the controller. Only
two more adjustments are required; RATE and RESET.
ECLIPSE INSTRUMENTATION DIVISION
page 3-1100
