Rockwell Automation Allen-Bradley 1790D-N0C2, Руководство пользователя

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20 Rockwell Automation Publication 1790-UM001B-EN-P - April 2021
Chapter 2 Installation and Wiring
As output impedance (Rs) and/or resistance (DC) of the cable (Rc) get larger,
system accuracy decreases. If you determine that the inaccuracy error is
significant, implement the following equation in the control program to
compensate for the added inaccuracy error due to the impedance of the output
module and cable.
Wiring the Modules
After the analog module is properly installed, follow the wiring procedure
below. To ensure proper operation and high immunity to electrical noise,
always use Belden 8761 (shielded, twisted-pair) or equivalent wire.
To wire your module, follow these steps.
1. At each end of the cable, strip some casing to expose the individual wires.
2. Trim the signal wires to 5.08 cm (2 in.) lengths. Strip about 5 mm (3/16
in.) of insulation away to expose the end of the wire.
3. At one end of the cable, twist the drain wire and foil shield together.
Under normal conditions, this drain wire and shield junction must be
connected to earth ground, through a panel or DIN rail mounting screw
at the analog I/O module end. Keep the length of the drain wire as short
as possible.
In environments where high frequency noise is present, ground the cable
shields to earth at the module and via a 0.1 μF capacitor at the sensor end
for analog inputs and at the load end for analog outputs.
4. At the other end of the cable, cut the drain wire and foil shield back to the
cable.
In a current loop system, source and cable impedance do not impact
system accuracy.
ATTENTION: To prevent shock hazard, care should be taken when
wiring the module to analog signal sources. Before wiring any analog
module, disconnect power from the system power supply and from
any other source to the analog module.
ATTENTION: Never connect a voltage or current source to an analog
output channel.
ATTENTION: Be careful when stripping wires. Wire fragments that fall
into a module could cause damage at power-up.
V
s
= V
load
x
[R
s
+ (2 x R
c
) + R
load
[R
load
]
Cable
signal wire
signal wire
drain wire
foil shield
signal wire
signal wire
Cut foil shield and drain wire