TM 5-3895-374-24-2955-2575)The PB is now very near its "CRITICAL" setting. Carefully increase or decrease the PB setting until cycles oroscillations 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 belowand 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 settingyou 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 obtainthe 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 thePB control until the desired final temperature deviation is achieved.NOMOGRAM I9)You have now completed all the necessary measurements to obtain optimum performance from the controller. Onlytwo more adjustments are required; RATE and RESET.ECLIPSE INSTRUMENTATION DIVISIONpage 3-1100
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