Omega-vehicle-security OMP-MODL Manuel d'utilisateur télécharger pdf (Page 52)

3... INTERFACE MODULES

USING THE OMP-MODL3-28

To minimize noise pickup on sensor wiring between the OMP-MODL and the

end sensor or signal source, 18 to 22 AWG shielded, twisted pair wire is

recommended. At the low current levels input to the MLIM-1, voltage drop

in signal wiring is not a concern, however for extremely long runs, a voltage

drop analysis should be performed for the entire loop and if necessary larger

gauge wire should be used.

FYI: Typically, with current signals (in contrast to low

level voltage signals), noise pickup will be less due to the

low impedances involved in the circuit. However, in real-

world applications, one should attempt to minimize noise

on signal wires whenever possible... remember, Mother

Nature loves to throw surprise parties.

Shielded wire minimizes the amount of noise picked up

by the internal conductors carrying the signals by

providing an `electrical shell’ or Faraday cage around the

internal conductors.

Twisted pair wiring exposes both conductors equally to

the ambient electrical noise. This common-mode type

noise is easier to reject by the Interface Modules input

signal conditioning circuitry than un-balanced (or

differential) noise.

Shielding and/or twisted pair wire is especially recommended in electrically

noisy environments for optimum signal protection. If shielded wire is used, a

ground wire should be run from the MLAD-1 module Chassis Ground

(terminal strip connection #16) to an earth ground connection to conduct

away noise picked up by the wiring shield (Figure 2-8). Only one ground

wire is required as all of the Shield terminal strip connections are

Terminal Strip

ml057

4-20mA

Panel Meter

+ XTMR -

4-20mA

Controller

Power

Supply

+ XTMR -

+ -

GND

1 2 3 4 5 6 7

Figure 3... -16: Terminal strip connections for multiple 4-20mA inputs

1 2 ... 47 48 49 50 51 52 53 54 55 56 57 ... 296 297

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Omega-vehicle-security OMP-MODL Manuel d'utilisateur Page 52

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