Measurement Computing PointScan 300 Series rev.1.0 - Manual (Page 29)

PointScan/300 User’s Manual 9-12-01 Analog Input Modules 6-1
Analog Input Modules 6
This section documents the following modules:
PointScan/301 PointScan/302 PointScan/303
PointScan/304 PointScan/305 PointScan/306
Power Requirements
The internal analog input circuitry is powered by the gateway through the PT-Bus wiring. External power is
required only for 4-20 mA loop signals coming from an unpowered source.
Analog Isolation
The PT-Bus wiring between PointScan/300 Series modules is isolated to a rating of 1,200 volts. Therefore,
all PointScan/300 Series modules are isolated from one another. In addition, the PointScan/304 module
provides 50 volt channel to channel isolation.
4-20 mA Input Circuit Jumpers
The PointScan/304 module has jumpers for connecting or disconnecting 100 ohm current shunts from each
input circuit. The PointScan/301 module has jumpers for providing 24 VDC loop power or instrumentation
ground to each field device. The jumpers are located behind the access door inside the module base. To
gain access to them, unplug the logic module from the base and open the access door. Refer to the
upcoming pages for more information on these jumpers.
These jumpers must be set to match the corresponding input signal type, regardless of software range
selection. Improper jumper selection could result in damage to the input circuitry.
Replaceable Current Shunts
PointScan/300 Series modules that support 4-20 mA inputs have a 100 ohm replaceable shunt for each
channel. These shunts are enabled by jumper settings, and are replaceable if damaged by an equipment
failure or wiring error.
These high precision shunts are located behind the access door inside the analog input module's base. A
spare shunt is provided in the base assembly for your convenience. These shunts are illustrated within the
diagrams of the applicable analog input modules.
If factory supplied shunts are used for replacements, recalibration of the input channels will not be
necessary.