Watlow Series 935A Manual de usuario descargar pdf (Pagina 34)

Auto-tuning

Auto-tune automatically sets PID parameters for your system.

1. Press . and , for three seconds.

2. You'll see [`Aut].

3. Press and hold ß, then select [`YES] with . or ,. [tune] will flash to indicate auto-tun-

ing. Display reverts to normal after auto-tuning.

4. [`Aut] = [``no] stops auto-tuning.

Figure 7 - Auto-tuning the Series 935A

Manual Tuning

For optimum performance, tune the Series 935A to your thermal system. The settings here are for a

broad spectrum of applications; your system may have different requirements.

Tune heating outputs at a set point above ambient temperature.

Tune cooling outputs at a set point below ambient temp.

1. Apply power to the 935A and enter a set point.

In the Operations Menu, [`Aut] must = [``no].

Begin with these Configuration Menu settings:

[Pb`h = [```1], [``1t] = [`000], [``dE] = [`000],

[Ct`h] = [`%0]], [`CAL] = [```0].

2. Proportional Band Adjustment: Gradually increase [Pb`h] until the upper display temp. stabilizes

at a constant value.

3. Integral Adjustment: Gradually decrease [``It] from 30.00 until the display temperature begins to

oscillate or “hunt.” Then slowly increase [``It] until the upper display stabilizes again near set

point.

4. Cycle Time Adjustment: Set [Ct`h] as required. Faster cycle times sometimes achieve the best

system control. However, if a mechanical contactor or solenoid is switching power to the load, a

longer cycle time will minimize wear on relays.

5. Derivative Adjustment: Increase [``dE] to 0.10 minute. Then raise set point by 20° to 30°F, or 11°

to 17°C. Observe approach to set point. If load temperature overshoots, increase [``dE] by 0.50

minute. Raise set point by 20 to 30°F, or 11 to 17°C and watch approach again. Repeat until sys-

tem rises to new set point appropriately.

6. Calibration Offset Adjustment: Enter the [`CAL] offset value you want. Calibration offset adds or

subtracts degrees from the value of the input signal.

Temperature

Time

90%

Set Point

32 Watlow Series 935A User’s Manual

Auto-tuning

NOTE:

[`Aut] is

not visible at

factory default.

CAUTION:

Successful Series

935A auto-tuning

requires 3

oscillations thru the

90% set point in 85

min. or less. If the

system cannot

perform the

oscillations in that

time, the control will

revert to the

previous PID values.

NOTE:

Manual tuning is a

slow procedure,

taking from minutes

to hours to obtain

optimum value.

Operations Menu

[`Aut]

✓

Auto-tune

[`ALO]

Alarm Range Low

[`Ah1]

Alarm Range High

[tMr]

Countdown Timer

[IdLE]

Idle

[`L-r]

Local / Remote

[`Pid]

PID

[CnFg]

Configuration

Auto-tuning occurs at 90% of set point

in less than or equal to 85 minutes.

1 2 ... 29 30 31 32 33 34 35 36 37 38 39 ... 67 68

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Watlow Series 935A Manual de usuario Pagina 34

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