DigitalFlow™ GC868 Startup Guide (1 and 2-Channel)
1-32
Chapter 1. Installation
Figure 1-40: Totalizer/Frequency Outputs Wiring
1.8.7
Wiring an RTD
Inputs Option Card
The Model GC868 can accommodate up to four RTD (Resistance Temperature
Device) input option cards. Each RTD input option card provides two direct RTD
inputs (designated as A and B).
Each RTD input requires three wires, which should be fed through one of the conduit
holes on the bottom of the electronic console. Wire this terminal block in accordance
with the pin number assignments shown in Figure 1-42 on page 1-43.
1.8.8
Wiring a 0/4-20
mA Analog
Outputs Option
Card
The Model GC868 flowmeter can accommodate up to 4 analog output option cards.
Each analog output option card includes four isolated 0/4-20 mA outputs
(designated as A, B, C and D).
Connections to these outputs may be made with standard twisted-pair wiring. The
total current loop impedance for these circuits must not exceed 1000 ohms. Wire this
terminal block in accordance with the pin number assignments shown in Figure 1-42
on page 1-43.
1.8.9
Wiring the
MODBUS Option
Card
The modified GC868 uses the RS485 standard for MODBUS communications. This
standard allows up to 32 nodes (drivers and receivers) on one multidrop network, at
distances up to 4,000 ft (1,200 m). To connect the instrument(s) to the control
system, Panametrics recommends using a 24-gauge (24 AWG) twisted-pair cable
with a characteristic impedance of 120 ohms and a 120-ohm termination at each
end of the communications line.
The MODBUS option card must be plugged into either slot 5 or slot 6 of the GC868. On
the option card, pin 1 is the
[TMT-]
inverting or negative connection and pin 2 is the
[TMT+]
non-inverting or positive connection. To link the GC868 to the control system,
connect the two wires of the twisted-pair cable from these terminals to the
corresponding terminals at the control system.
NO
C
IN
Common
Volts –
(Common)
Volts +
(Int. Pwr. Sup.)
NO
C
+5V
200
Model GC868
Model GC868
Pulse Counter
Frequency Counter
Totalizer Output
Frequency Output
Load
Max. Current: 4A
Max. Voltage: 150V
Isolation Voltage: 500V
Max. Load Power: 10W In
C = Isolated Return
C = Isolated Return
