Pulsafeeder Pulsa Series Pulsamatic Controls - Manual (Page 14)

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6. Repairs
6.1 Limit Switch Adjustment
This procedure adjust the limit switches to prevent the pump mechanism from jamming due to
over travel, without significantly restricting the range of stroke length settings.
The limit switches disable the actuator from operating below zero strokes or above full stroke,
either of which can cause jamming. For this reason, correct limit switch adjustment is very
important.
The procedure for checking limit switch adjustment is given under “Installation- Start Up”. As
stroke length is manually decreased, the switch closest to the circuit board should open (disabling
decrease clutch voltage) at as stroke indicator reading between (001) and (000). This reading must
not be below (000). As stroke length is manually increased, the switch farthest from the circuit
board should open (disabling increase clutch voltage) at a stroke indicator reading between 099
and 100. This reading must not be above 100.
To adjust a limit switch, loosen its two mounting screws, slide it in the required direction and
tighten the screws. Verify the adjustment as described under “Installation- Start Up”.
6.2 Potentiometer
1. Record the color codes of the potentiometer leads to TB2-3, 4, and 5, and disconnect them
from TB2.
2. Verify full potentiometer resistance of approximately 1000 ohms between the leads removed
from pins 4 and 5.
3. A needle type (analog) meter is recommended for checking potentiometer operation. As the
potentiometer gear is turned counterclockwise, the resistance between leads removed from
pins 5 and 3 should vary uniformly from zero to approximately 1000 ohms.
As the potentiometer gear is turned clockwise, the resistance should vary uniformly from
approximately 1000 ohms to zero.
4. If the extreme readings vary significantly from zero and 1000 ohms respectively or if the
resistance variation with rotation is not smooth at any point, the potentiometer should be
replaced. If the directions of rotation are the reverse of those stated above, then the
potentiometer has been wired for reverse acting operation.
5. To replace the potentiometer assembly, assure that pump has been turned manually to the
“000” indicator setting. Turn the potentiometer gear full clockwise (see from the gear end)
then back counterclockwise ¼ turn.
6. Install the potentiometer and reconnect leads to the circuit board.