19
Model 580A Differential Pressure Switch
Section 3
Linkage Calibration Procedure
The switch linkage should be calibrated whenever the Model 580A switch has
been rebuilt.
To calibrate the switch linkage, perform the following steps. Refer to
Figure
3.7
as needed.
1. Loosen the three linkage screws and turn the crank to the 12 o’clock
position.
2.
Use a 1/8-inch Allen wrench to hold the index shaft and slip the index
pointer to 0 on the switch index. Tighten the screw on the crank to the
mid-slot position to set the crank radius.
3.
Turn the index pointer to index number "1" on the outer edge of the
switch index.
4.
Apply 10% differential pressure and adjust the switch plate
until the
switch actuates. Lock the two linkage screws.
5.
Rotate the index pointer to index number “9.” Apply 90% differential
pressure and adjust the crank radius until the switch actuates.
6. Recheck 10% and 90% set points. Adjust the crank radius and the index
pointer until both set points are accurate within a 2% tolerance (nominal).
Figure 3.7—Linkage arrangement
7. If the switch is to be field-set at low differential pressure values (1% or
2% of pressure range), check the crank to prevent a 12 o'clock position.
Otherwise, the minimum set point position will be restricted and the set
point may become reversed.
8. Adjust the low switch to actuate at the desired pressure by applying test
pressures in a decreasing direction, in discrete steps. Allow the unit and