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omega
.com
CONFIGURATION
Analog Output (4-20mA) Configuration.
(Not available on battery only units.)
Since the meter’s analog output is isolated and passive, loop power must be supplied externally as shown previously.
(In addition, an external resistor R
L
will be needed to convert the loop current to voltage for voltage-only input devices.)
The meter’s loop transmitter minimum voltage drop is 6Vdc which, with wiring resistance and loop power supply
voltage, will determine the maximum resistance for R
L
.
The flow rates corresponding to 4 and 20mA can be set by the user via the SET 4 and SET20 tabs on the meter’s setup menus.
Modbus
®
Serial Communication Configuration (
factory configured
).
These connections provide a half-duplex, isolated, RS485 serial communications port using the Modbus
®
messaging
protocol. The TXD connection is the transmitted data output from the meter and RXD is the received data input to the
meter. See
Modbus
®
Interface Description, LT-103393 (available at
omega
.com) for supported Modbus
®
message
protocol and electrical interface specifications.
A 120-ohm termination resistor is built into the Modbus
®
option board but is shipped in the unused position.
To engage the termination resistor, move the jumper on JP1 from position 3-4 to position 1-2.
Note: As configured by the factory, any alarm state will force 22.8mA on the loop.
This can be changed to 3.2mA - see Technical Bulletin, ‘iMAG4700/AG3000: Changing the 4-20mA Alarm’
FMG470 Series
