Chapter 3 Electrical Installation; Cable Length Ttl Mode; Cable Length Open Collector Mode - Emerson Rosemount 3410 Series Installation Manual

Installation manual
00825-0600-3104
3 Electrical installation
3.1

Cable length TTL mode

The maximum cable length is 2000 feet (609.6 m) when the Digital Output "TTL" mode is
selected.
3.2

Cable length Open Collector mode

For the Digital Output open collector mode, the maximum cable length depends on
the cable parameters, pull-up resistance used, the maximum frequency to output, and
frequency input parameters being driven. The following table provides estimated cable
lengths for different pull-up resistor values and different Max Frequency settings in the
meter using the following cable parameters. The table also provides an estimated cable
voltage drop which indicates how much voltage will be across the cabling and effectively
indicates to what voltage level the frequency input can be pulled down to by the frequency
output.
If the voltage drop is higher than the voltage required for the frequency input to see a
low state, then the configuration will most likely not work for your system. Performance of
frequency outputs will vary from this table with setup and frequency input being driven.
Table 3-1: Configurations for open collector frequency outputs
Cable Cable
resistance
Length (2 Conductors)
(x1000 ft) Ω
0.5 16.8
1 33.6
2 67.2
4 134.4
0.5 16.8
1 33.6
1.7 57.12
6.5 218.4
The 22 AWG wire characteristics:
• Capacitance = 20 pF/ft. or 20 nF/1000 ft. (between two wires)
• Resistance = 0.0168 Ohms/ft or 16.8 Ohms/1000 ft
• Pull-up voltage = 24 Vdc
Installation manual
Cable Pull-up
resistance
Capacitance Resistance Ω Resistance Ω
nF
10.00 1000
20.00 1000
40.00 1000
80.00 1000
10.00 500
20.00 500
34.00 500
130.00 500
Total Maximum
frequency
Frequency
(Hz)
1016.8 5000
1033.6 1000
1067.2 1000
1134.4 1000
516.8 5000
533.6 5000
557.12 5000
718.4 1000
Electrical installation
October 2023
Sink Cable voltage
drop
Current (A) (2 Conductors)
Vdc
0.024 0.397
0.023 0.780
0.022 1.511
0.021 2.843
0.046 0.780
0.045 1.511
0.043 2.461
0.033 7.296
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