RP922A PneumaticPotentiometer
Copyright © 1983 Honeywell Inc. • All Rights Reserved 77-5053
SPECIFICATION DATA
GENERALThe RP922A is a three-port pneumatic potentiometer. It is amultipurpose device used in control systems for the following:
— Sum of two input pressures— Average of two input pressures— Adjustable flow restriction— Adjustable pressure supply
FEATURES• High efficiency integral filters for all ports• High reliability, no internal moving parts• Compact size• High accuracy
2
RP922A PNEUMATIC POTENTIOMETER
77-5053
SPECIFICATIONSOperating Temperature:39 to 122F 4 to 50C)
Operating Pressure:0 to 20 psi (0 to 138 kPa)
Maximum Safe Air Pressure:30 psi (207 kPa)
Air Connection:5/32 in. (4 mm) push-on barb
Air Consumption:— Sum of two input pressures: none— Ratio of two input pressures: none— Adjustable flow restriction: none— Adjustable pressure supply application: 0.007 scfm
(0.00331/sec) at 14.5 psi (101 kPa)
Mounting:Snap-on device rail mounting or mounting on walls or panelswith screws.
Dimensions:See Figure 1.
Fig. 1. RP922A dimensions in inches (millimeters).
TYPICAL OPERATION1. Averaging-Ratio Relay, Summing Relay
— A typical application uses the RP922A to provideaveraging-ratio pressure output. P1 and P3connect to pressure signals and P2 connects to acontroller input port. P2 is a functional output ofP1 and P3 (Fig. 2 and Table 1).
— The RP922A sums the input velocity signals oftwo ducts with different areas to produce a totalflow signal (Fig. 3).
Fig. 2. Averaging-Ratio relay application.
Table 1. Ratio pressure at port 2. 1
Ratio Output at P2 Scale Setting
9-1 9 P1 + P310
10
3-1 3 P1 + P34
25
2-1 2 P1 + P33
33
1-1 P1 + P32
50 (Averaging)
1-2 P1 + 2 P33
67
1-3 P1 + 3 P34
75
1-9 P1 + 9 P310
90
1 Idealized Response. Actual response is higher thanthe calculated response by about 5 percent of theP1, P3 difference.
2. Adjustable Flow Restriction— A typical application uses the RP922A to function
as an adjustable airflow restriction. Thirty percentscale setting is equivalent to an 0.007-inchrestrictor, ninety percent scale setting isequivalent to an 0.005-inch restrictor (Fig. 4).
3. Adjustable Pressure Supply— The RP922A provides an adjustable pressure
from 10 to 90 percent of the pressure at Port P1(Fig. 5 and Fig. 6).
— The RP922A widens the effective proportionalband of a controller by reducing the sensor inputpressure by a fixed ratio (i.e., at a scale setting of50, controller pb is doubled) (Fig. 7 and Table 1).
2-7/8 (73)
2-1/2 (64)
2-7/16 (62)
++
50 4030
20
1090
8070
60
++
+ +
C7865
12
3
MM
SENSORS
RP922
INPUT
CONTROLLER
1 2 3
C7859
RP922A PNEUMATIC POTENTIOMETER
3 77-5053
Fig. 3. Summing relay application.
Fig. 4. Adjustable flow restrictor application.
Fig. 5. Adjustable pressure supply application.
Fig. 6. Output pressure vs scale settings.
Fig. 7. Adjustable sensor input span application.
TO TOTAL CFM FLOW SIGNAL
VELOCITY SIGNAL 1
VELOCITY SIGNAL 2
1 2 3
C7860
TO CONTROLLED DEVICE
CONTROL SIGNAL
INPUT PRESSURE
1 2 3
C7861
DEAD ENDED PORT
CONTROL SIGNAL
INPUT PRESSURE
1 2 3
C7862
OU
TP
UT
PE
RC
EN
TA
GE
OF
INP
UT
PR
ES
SU
RE
SCALE SETTINGC7863
90
90 20 30 40 50 60 70 80 90
70
50
30
10
TO CONTROLLER INPUT (BLOCKED PORT)
RP970A
RP922A
3
4 1 2
SENSOR
1 2 3
C7864
M
M
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Helping You Control Your World
77-5053 11-83
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