CONTROL POINT ADJUSTMENT (CPA Models Only)
COMPENSATION STARTPOINT ADJUSTMENT (RP920B and
D)
1.
Pipe the CPA device to Port 9.
NOTE:
A 1 psi change in the CPA pressure causes a
change of 2.5 percent of the primary sensor
span.
2.
Set the CPA to the center of its range when calibrating
controllers. For example: Set the CPA to 9 psi (62 kPa)
for a 3- to 15-psi (21 to 103 kPa) signal range.
PROPORTIONAL BAND ADJUSTMENT
Adjust the Proportional Band (PB) according to the job
drawings with the proportional band adjustment knob (Fig.
14).
PB = Operating Throttling Range
Primary Sensor Span
AUTHORITY ADJUSTMENT (RP920B and D)
Adjust the authority according to the job drawings with
the authority adjustment knob (Fig. 14). Calculate the
authority setting as follows:
Negative compensation:
ASC
Positive compensation:
A
C
x
Where (in measured variable units):
A
C
= Authority
ASC = Compensation sensor operating range
s c s = Compensation sensor span
ASP = Primary sensor operating range
SPs
Primary sensor span
Throttling range in measured variable (use 0
for RP920D)
If the authority is greater than 300 percent or
must be calculated using pressure units, see
RP920A-D Modular Pneumatic Controller
Engineering Data 77-6082.
NOTE: Calibration can cause the actual
authority setting to vary from the
calculated value.
Adjust the compensation startpoint according to the job
drawings with the compensation startpoint adjustment
knob (Fig. 14). If the startpoint is not in percent, convert it
to a percentage of the compensation sensor range. See
APPENDIX A.
RESET TIME ADJUSTMENT (RP920C
and
D)
Adjust the reset time according to the job drawings
with
the
reset time adjustment knob (Fig, 14). When the system
is in operation and stable, decrease the setting a little at a
time until
the system becomes unstable. Increase the setting
slightly until the system becomes stable.
COVER
a cover is used, snap it straight on from the front. The
cover is secured by tightening the self-tapping screw in the
lower right comer.
13
85-O 142
