2Ć1
2.0 MECHANICAL/ELECTRICAL
DESCRIPTION
The following is a description of the faceplate LEDs, field termination
connectors, and electrical characteristics of the field connections.
2.1 Mechanical Descrip ion
The input module is a printed circuit board assembly that plugs into
the backplane of the DCS 5000/AutoMax rack. It consists of a printed
circuit board, a faceplate, and a protective enclosure. The faceplate
contains tabs at the top and bottom to simplify removing the module
from the rack. Module dimensions are listed in Appendix A.
The faceplate of the module contains a female connector socket and
4 LED indicators that show the status of the inputs. Input signals are
brought into the module via a multiĆconductor cable (M/N 57C371;
see Appendix D). One end of this cable attaches to the faceplate
connector, while the other end of the cable has stakeĆon connectors
that attach to a terminal strip for easy field wiring. The faceplate
connector socket and cable plug are keyed to prevent the cable from
being plugged into the wrong module.
On the back of the module are two edge connectors that attach to
the system backplane.
2.2 Elec rical Descrip ion
The input module contains two analog input channels with
softwareĆselectable filters. These channels are connected through a
multiplexer to a successive approximation analog to digital converter.
As supplied, the module can convert +10 volt or +1 volt inputs. If
you add external resistors, the module can convert +5 volt or 4Ć20
ma current inputs.
Each channel provides 12 bit conversion plus sign (+4095). The
module provides 100% overranging in the event that the input signal
exceeds the maximum normal input voltage. hen in the overrange
condition, the magnitude is doubled (+8191) and the accuracy is
halved (bit 0 is no longer significant).
The analog to digital converter provides conversion rates as fast as
once every 500 microseconds. The update period is software
programmable in increments of 500 microseconds, up to a maximum
of 32.7675 seconds. Sample and hold circuits maintain constant
input values during conversion.
Each channel contains a low pass filter with userĆselectable
bandwidths to smooth out transients and also provide antiĆaliasing
for signals with high frequency components. The filter cutoff
frequencies are given in figure 4.6.
A single isolated common is provided for both analog input channels.
Input signals have 600 volt isolation to logic common. An onĆboard
DCĆDC converter provides power to the isolated portion of the circuit.
The +15 volt outputs from the supply are brought to the connectors
on the faceplate of the module. A circuit diagram is shown in figure
2.1. Refer to Appendix A for power supply current limitations.
