Watlow Series 982 User Manual download pdf (Page 110)

8.2 WATLOW Series 982 User’s Manual

Tuning, Alarms and Error Codes, Chapter 8

Tuning

To start auto-tuning:

1.Press the Mode key until the AUt prompt appears in the lower display.

2. Use the Up/Down key to select Pid in the upper display.

3.Press the Display key. While the control is in the tuning mode, the

lower display alternately displays the normal information and the tunE

prompt. The time between alternations is 1 second.

4.When tuning is complete, the displays return to their previous state

and AUt reverts to OFF. The 981/982 installs appropriate PID tuning

parameters and saves them in non-volatile memory.

To abort auto-tuning either reset the AUt prompt to OFF, or cycle power

off and on. In all cases, aborting auto-tune restores all values to those pre-

vious to auto-tuning.

Manual Tuning ç

For optimum control performance, tune the Series 981/982 to your ther-

mal system. The tuning settings here are for a broad spectrum of applica-

tions; your system may have somewhat different requirements. NOTE:

This is a slow procedure, taking from minutes to hours to obtain optimum

values.

NOTE:

Tune heating outputs at a set point above

ambient process value.

Tune cooling outputs at a set point below ambient process value.

NOTE:

1.Apply power to the Series 981/982 and enter a set point. Begin with

these Operation parameters: Pb = 1, rE/It = 0.00, rA/dE = 0.00, Ct =

5.0,

AUT = OFF.

2.Proportional Band Adjustment: Gradually increase Pb until the

upper display process value stabilizes at a constant value. The process

value will not be right on set point because the initial reset value is 0.00

repeats per minute. (When Pb = 0, rE/It, rA/dE and cycle time are

inoperative, the 981/982 functions as a simple ON/OFF control.) The

HYS prompt determines the switching differential value.

3.Reset/Integral Adjustment: Gradually increase rE, or decrease It until

the upper display process value begins to oscillate or “hunt.” Then slowly

decrease rE or increase It until the upper display stabilizes again near

set point.

4.Cycle Time Adjustment: Set Ct as required. Faster cycle times some-

times achieve the best system control. See Chapter 9, “Burst Firing,” for

more information. However, if a mechanical contactor or solenoid is

switching power to the load, a longer cycle time may be desirable to

CAUTION:

If a mechanical

relay or contactor is

switching power to

the load, a longer

cycle time may be

desirable to mini-

mize wear on the

mechanical compo-

nents. Typical life of

a mechanical relay

is 100,000 cycles.

CAUTION:

If a mechanical

relay or contactor is

switching power to

the load, a longer

cycle time may be

desirable to mini-

mize wear on the

mechanical compo-

nents. Typical life of

a mechanical relay

is 100,000 cycles.

NOTE:

You cannot access

the AUt prompt

while the controller

is in run mode.

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Watlow Series 982 User Manual Page 110

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