Emerson Rosemount OCX 8800 - Differential Pressure Transmitter to Measure Flow; Troubleshooting

7.8.16 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 7-25 lists the appropriate configuration settings, and Figure 7-11 illustrates the
correct function block configuration.
Analog input function block configuration for a differential pressure
measurement
Table 7-25:
Parameter Configured values
L_TYPE Indirect square root
XD_SCALE 0 to 20 in.
OUT_SCALE 0 to 800 gal/min
Function block diagram for a differential pressure transmitter used in a
flow measurement
Figure 7-11:
7.8.17 Troubleshooting
Refer to Table 7-26 to troubleshoot any problems that you encounter.
TroubleshootingTable 7-26:
Symptom Possible cause Corrective action
Mode will not leave OOS. 1. Target mode not set 1. Set target mode to something oth-
er than OOS.
Foundation Fieldbus
Reference Manual 147