535-PROF User's Manual
Chapter 7
117
Applications
W. RATIO CONTROL
Ratio Control is employed in mixing applications that require the materials to be
mixed to a desired ratio.
For example:
A given process requires Material A to be blended with Material
B in a 2:1 ratio. Material B is uncontrolled or wild. Flow sensors/transmitters are
used to measure the flow rate of each stream. The flow signal for Material A is
wired to the process variable input, and the flow signal for Material B is wired to
the remote setpoint input of the 535.
For this example, as shown in
Figure 7.22, we would set
RSP RATIO
to 2.0. If
the flow of Material B is measured at 50 gallons/minute, the effective remote
setpoint value would be 2 times 50, or 100. The 535 controller would try to maintain
the flow of Material A at 100. As the flow of Material B changes, the setpoint
would change accordingly, always in a 2:1 ratio.
Figure 7.22
Ratio Control in Mixing Applicatoin
1
2
3
4
5
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7
8
16
15
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11
10
9
17
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32
31
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25
BOTTOM
(As viewed from rear)
EARTH GND
PV 1+
PV 1-
AC+
AC-
OUT 1-
OUT 1+
MIXER
CONTROLLED STREAM
RSP+
RSP-
flow
sensor
WILD STREAM
MATERIAL B
MATERIAL A
flow
sensor
