Cam Selection - ABB AV1 Operating Instructions Manual

Table C-1. Control Signal Pressure Conversions (AV1)
Control System Spans
% of
20.7 to 103.4 kPa
Control
(3.0 to 15.0 psig)
Signal
kPa psig
0 20.7 3.0
10 29.0 4.2
20 37.2 5.4
30 45.5 6.6
40 53.8 7.8
50 62.1 9.0
Table C-2. Input to Output I/P Converter Relationships (AV2)
I/P Converter
% of
Control Input
Signal
mA
0 4.0
10 5.6
20 7.2
30 8.8
40 10.4
50 12.0

CAM SELECTION

Table C-1 relates the percentage of control signal to the corre-
sponding pressure values of the input signal. Table
percentage of control signal to input (current) and output (pounds
per square inch gage) values of the I/P converter.
% of
20.7 to 186.2 kPa
Control
(3.0 to 27.0 psig)
Signal
kPa psig
20.7 3.0 60
37.3 5.4 70
53.8 7.8 80
70.4 10.2 90
86.9 12.6 100
103.5 15.0
% of
Output Control
Signal
kPa psig
20.7 3.0 60
29.0 4.2 70
37.2 5.4 80
45.5 6.6 90
53.8 7.8 100
62.1 9.0
In a system involving only a single actuator or cylinder, the B cam
is probably satisfactory and should be tried first. However, one of
the other cams may provide a more stable control over a wide
range of operation within a given proportional band gain adjust-
ment on the controller. Where the actuator or cylinder is part of a
complex control system, the three standard cams A, B and C pro-
vide a choice of control characteristics. The cam, in conjunction
with a span adjustment, are likely to meet the control characteris-
tic required for the system.
Steps is selecting a standard cam for a particular application are:
1. With the B (linear) cam in place, determine and plot the actual
controlled medium versus piston (or valve) position characteristic
by manually adjusting valve position and measuring the controlled
medium (Fig. C-4).
CAM CHARACTERIZATION
C-2
Control System Spans
20.7 to 103.4 kPa 20.7 to 186.2 kPa
(3.0 to 15.0 psig) (3.0 to 27.0 psig)
kPa psig kPa
70.3 10.2 120.0
78.6 11.4 136.6
86.9 12.6 153.1
95.2 13.8 169.7
103.4 15.0 186.2
I/P Converter
Input Output
mA kPa
13.6 70.3
15.2 78.6
16.8 86.9
18.4 95.2
20.0 103.4
CAM SELECTION
relates the
psig
17.4
19.8
22.2
24.6
27.0
psig
10.2
11.4
12.6
13.8
15.0
C - 3