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Instruction Manual
IM-106-880C, OI
September 2009
7-33
Hazardous Area OCX 8800
Differential Pressure Transmitter to Measure Flow
Situation
The liquid flow in a line is to be measured using the differential pressure
across an orifice plate in the line, and the flow measurement will be used
in a flow control loop. Based on the orifice specification sheet, the
differential pressure transmitter was calibrated for 0 to 20 in H
2
0 for a flow
of 0 to 800 gal/min, and the transducer was not configured to take the
square root of the differential pressure.
Solution
Table 7-24 lists the appropriate configuration settings, and Figure 7-12
illustrates the correct function block configuration.
Table 7-24. Analog Input
Function Block Configuration for
a Differential Pressure
Measurement
Figure 7-12. Function Block Diagram for a Differential Pressure Transmitter Used in a Flow Measurement
Parameter Configured Values
L_TYPE Indirect Square Root
XD_SCALE 0 to 20 in.
OUT_SCALE 0 to 800 gal/min
38740089
AI
Function
Block
PID
Function
Block
AO
Function
Block
OUT_D
OUT
Analog
Measurement
BKCAL_INBKCAL_OUT
IN