Measurement Computing PointScan 300 Series rev.1.0 - Manual (Page 31)

PointScan/300 User’s Manual 9-12-01 Analog Input Modules 6-3
PointScan/301
4-20 mA Input Module
This 4-20 mA analog input module has eight channels that accept 4-20 mA signals from self powered or
loop powered devices. Two screw terminals are provided for each input channel. The return screw
terminals are tied through movable jumpers to +24 volts DC or to instrumentation ground.
Open Loop Detection Feature
The Remote IO Toolkit configuration program provides a selection that allows inputs below
4 mA to be reported as zero, or be reported as negative values to detect loop failure.
Replaceable Current Shunts
This module base has replaceable 100 ohm current shunts, should a faulty field device or wiring error cause
the original shunt to overheat. To access these shunts, unplug the logic module from the base and open the
access door. A spare shunt is provided.
4-20 mA Input Scaling
Current inputs are reported as unscaled values from 0 to 32767. Refer to the Remote IO Toolkit online help
system for more information.
Loop Power Jumpers
If any of your 4-20 mA transmitters require loop power, connect 24 VDC to terminals 17 and 18 of the
module base as shown below. (The 24 VDC may come from an external DC power source, or from the
power supply.) Then set the loop power jumper for each unpowered loop input channel to the DC+
position. For all self-powered 4-20 mA input field devices, set the loop power jumper to the GND position
to provide a ground reference for the input channel.
The loop power jumpers are located inside the module base, and may be accessed by removing the plug-in
logic module and opening the access door.