Athena 2000 Series Instruction Manual - Page 12

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Adjustments

NOTE: Each

process will tolerate

differing warm-up

curves. Often, a fast

warm-up is more

important than the

elimination of over-

shoot. If it is impor-

tant to eliminate

overshoot, a slower

setting should be

used, but it will also

add to the time it

takes the process to

reach the setpoint.

In general, it is

best to maintain the

tightest parameters

possible (narrow

proportional band,

faster reset, faster

rate) that still deliver

optimal process

response.

Maintenance

CAUTION:

Since the front

panel and the

meter face are

plastic, do not

use solvents to

clean them.

until it finally stabilizes, the reset time is correct.

Then proceed to Step 7. If it continues to oscillate,

reset it to short, continue with Step 6.

6. Set reset switches to the next slowest time.

Repeat Step 5. Continue changing settings until

the process stabilizes.

7. Turn proportional band pot 1/4 turn toward nar-

row (counterclockwise). Process could begin to

oscillate again. If it doesn't, proceed to step 8. If it

oscillates, back up 1/8 turn clockwise.

8. Tighten proportional band by turning the pot

counterclockwise. Observe the process. If oscilla-

tion continues, widen back by 1/8 turn. Continue

until the process stabilizes.

9. Set the rate. Rate action responds to sudden load

changes and anticipates power output require-

ments. It also helps to eliminate overshoot on start-

up. Rate should be approximately 1/6 of reset time.

If the reset time is 0.8 minutes, the rate should be

turned clockwise. For 1 minute, mid-position. For 2

minutes, it should be at least 3/4 full; for 4 minutes

full slow.

10. Turn the process off to cool, then start up

again observing the warm-up curve. If it takes

the process too long to reach the setpoint, make

the rate faster by turning it back clockwise. If, on

the other hand, it overshoots the setpoint by an

amount that is not acceptable, slow the rate by

turning the pot counterclockwise.

11. Fine tuning. If, after having established parame-

ters, you'd like to improve response, it can be

accomplished by a simple "trial and observation"

technique.

A. Change a parameter (either rate or proportional

band) by a significant value (the pots generally

need to be moved 30° to produce an effect).

B. Change the setpoint.

C. Observe the way the process responds

-- if response is improved (i.e., faster rise, less

overshoots, faster stabilization at setpoint),

retain the new value. If not, return the old value.

D. Try another parameter.

Some preventive maintenance steps on the controllers are:

1. Keep the controller fairly clean, and protect it from

dirt, oil, and corrosion. An optional dust cover is

available for use in hostile environments.

2. Periodically recheck all electrical connections.