Comptus A70-DL0, Instruction Manual

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8
INSTALLATION
Wiring Considerations
The wire type is noncritical for most applica-
tions. If the wiring is located in an electrically
noisy environment, or longer than 60 feet a twisted
pair with shield is recommended. Connect the shield
to ground at one end only, see Figure 6. The insula-
tion should be sunlight resistant. Polyethylene or
polyvinyl chloride insulation is recommended.
Before proceeding verify that the maximum
resistance of the current loop including the
wiring and sensing element does not exceed the
maximum given by Formula 1. If this resistance
is exceeded the loop current will not attain full
scale.
Formula 1
Maximum Loop Resistance
R - Maximum Loop Resistance in Ohms
V - DC Excitation Voltage
R = (V - 10 Vdc) X 50
The resistance of various gages of copper wire is
given in Table 1.
Table 1
Wire Gage Resistance in
AWG Ohms per foot
12 .0016
14 .0026
16 .0041
18 .0065
20 .0103
22 .0165
24 .0262
A70-DL POWER SUPPLY
Proper operation of the Transmitter requires that
the power supply provide a voltage in the range
of 12-24 VDC. Voltage ripple must be less than
100 volts per second for proper operation. The
Transmitter is designed so that the loop current
will not exceed approximately 30 ma under any
circumstances.
A 12 volt power supply can drive a current loop
with a total resistance of 150 ohms. A 16 volt
power supply can drive a current loop with a
total resistance of 450 ohms.
Figure 8
Graph of Maximum Loop Resistance
voltage
Excitation
Minimum
Excitation Voltage
10 14 18 22 26
300
100
0
200
Resistance
Total Loop
600
400
500
Ohms
A96-100P Surge Arrestor