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Installation manual
3-9000-771
3
Electrical Installation
3.1
Cable length TTL mode
The maximum cable length is 2000 feet when the "TTL" mode is selected.
3.2
Cable length Open Collector mode
For the "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
Length
(x1000ft)
0.5
1
2
4
0.5
1
1.7
6.5
The 22 AWG wire characteristics are as follows:
•
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 is 24 VDC
Installation manual
Cable
Cable
Pull-up
resistance
resistance
(2
Capacitan
Resistance Resistance Frequency Current
Conductor
ce
s)
Ω
nF
Ω
16.8
10.00
1000
33.6
20.00
1000
67.2
40.00
1000
134.4
80.00
1000
16.8
10.00
500
33.6
20.00
500
57.12
34.00
500
218.4
130.00
500
Electrical Installation
Total
Maximu
Sink
m
frequency
Ω
(Hz)
(A)
1016.8
5000
0.024
1033.6
1000
0.023
1067.2
1000
0.022
1134.4
1000
0.021
516.8
5000
0.046
533.6
5000
0.045
557.12
5000
0.043
718.4
1000
0.033
May 2019
Cable
voltage
drop
(2
Conductor
s)
VDC
0.397
0.780
1.511
2.843
0.780
1.511
2.461
7.296
41
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