Chapter 1. Installation
16 DigitalFlow™ XGM868i Startup Guide
1.7.5c Wiring a 0/4-20 mA Analog Inputs Option Card
To calculate the standard flow rates, the Model XGM868i requires accurate temperature and pressure data from the
measurement site. Transmitters installed in the flowcell can provide this information via an optional 0/4-20 mA analog
inputs option card. This option card includes two or four isolated 0/4-20 mA analog inputs (designated as A, B, C and
D), each of which includes a 24 VDC power supply for loop-powered transmitters. Either input may be used to process
the temperature signal, while the other input is used to process the pressure signal.
Note: To properly enter programming data into the meter, it is necessary to know which input is assigned to which
process parameter. This information should be entered in Appendix B, Data Records.
The analog inputs, which have an impedance of 118 ohms, should be connected with standard twisted-pair wiring.
Power to the transmitters may be supplied either by the integral 24 VDC power supply on the analog input option card
or by an external power supply. Figure 5 shows typical wiring diagrams, with and without an external power supply, for
one of the analog inputs.
Figure 5: Analog Input Wiring Diagram
+24V
INPUT +
INPUT +
+24V
+–
+ IN
– OUT
+ IN
– OUT
Sensor
Sensor
Transmitter
Transmitter
Analog Input
Analog Input
24 VDC
POWER SUPPLY
With External Power Supply
With Internal Power Supply
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