Allen-Bradley MicroLogix 1200 RTD/Resistance User manual

Publication 1762-IN014B-EN-P - July 2013
Installation Instructions
MicroLogix 1200 RTD/Resistance Input Module
Catalog Number 1762-IR4
Topic Page
Module Overview 2
Description 2
Module Installation 3
System Assembly 4
Mounting 4
Field Wiring Connections 7
I/O Memory Mapping 15
Specifications 19
North American Hazardous Location Approval 22
Additional Resources 23

2MicroLogix 1200 RTD/Resistance Input Module
Publication 1762-IN014B-EN-P - July 2013
Module Overview
The 1762-IR4 module receives and stores digitally converted analog data from RTDs or other
resistance inputs, such as potentiometers. The module supports connections from any
combination of up to 4 RTDs or other resistance inputs. See the input specifications on page 20
for supported RTD and resistance types, their associated temperature ranges, and the analog
input signal ranges that each channel supports. Each of the 4 input channels is individually
configurable for a specific input device and provides open- or short-circuit and over- or
under-range indication.
Description
Item Description Item Description
1a upper panel mounting tab 5bus connector cover
1b lower panel mounting tab 6flat ribbon cable with bus connector (female)
2power diagnostic LED 7terminal block
3module door with terminal identification
label 8DIN rail latch
4bus connector with male pins 9pull loop
9
3
5
2
1b
1a
7
6
4
8
6
1a
1b
2

MicroLogix 1200 RTD/Resistance Input Module 3
Publication 1762-IN014B-EN-P - July 2013
Module Installation
1762 I/O is suitable for use in an industrial environment when installed in accordance with these
instructions. Specifically, this equipment is intended for use in clean, dry environments
(Pollution degree 2(1)) and to circuits not exceeding Over Voltage Category II(2) (IEC
60664-1).(3)
Prevent Electrostatic Discharge
Remove Power
(1) Pollution Degree 2 is an environment where, normally, only non-conductive pollution occurs except that occasionally a
temporary conductivity caused by condensation shall be expected.
(2) Over Voltage Category II is the load level section of the electrical distribution system. At this level transient voltages are
controlled and do not exceed the impulse voltage capability of the product’s insulation.
(3) Pollution Degree 2 and Over Voltage Category II are International Electrotechnical Commission (IEC) designations.
ATTENTION
Electrostatic discharge can damage integrated circuits or semiconductors
if you touch bus connector pins. Follow these guidelines when you handle
the module:
•Touch a grounded object to discharge static potential.
•Wear an approved wrist-strap grounding device.
•Do not touch the bus connector or connector pins.
•Do not touch circuit components inside the module.
•If available, use a static-safe work station.
•When not in use, keep the module in its static-shield box.
ATTENTION
Remove power before removing or installing this module. When you
remove or install a module with power applied, an electrical arc may occur.
An electrical arc can cause personal injury or property damage by:
•sending an erroneous signal to your system’s field devices, causing
unintended machine motion
•causing an explosion in a hazardous environment
•causing permanent damage to the module’s circuitry
Electrical arcing causes excessive wear to contacts on both the module and
its mating connector. Worn contacts may create electrical resistance.

4MicroLogix 1200 RTD/Resistance Input Module
Publication 1762-IN014B-EN-P - July 2013
System Assembly
The expansion I/O module is attached to the controller or another I/O module by means of a
ribbon cable after mounting as shown below.
Mounting
TIP
Use the pull loop on the connector to disconnect modules. Do not pull
on the ribbon cable.
WARNING
EXPLOSION HAZARD
•In Class I, Division 2 applications, the bus connector must be fully
seated and the bus connector cover must be snapped in place.
•In Class I, Division 2 applications, all modules must be mounted in
direct contact with each other as shown on page 5. If DIN rail
mounting is used, an end stop must be installed ahead of the
controller and after the last 1762 I/O module.
ATTENTION
Do not remove protective debris strip until after the module and all other
equipment near the module is mounted and wiring is complete. Once
wiring is complete and the module is free of debris, carefully the remove
protective debris strip. Failure to remove the strip before operating can
cause overheating.

MicroLogix 1200 RTD/Resistance Input Module 5
Publication 1762-IN014B-EN-P - July 2013
Minimum Spacing
Maintain spacing from enclosure
walls, wireways, adjacent
equipment, etc. Allow 50.8 mm
(2 in.) of space on all sides for
adequate ventilation, as shown:
DIN Rail Mounting
The module can be mounted using the following DIN rails: 35 x 7.5 mm
(EN 50 022 - 35 x 7.5) or 35 x 15 mm (EN 50 022 - 35 x 15).
Before mounting the module on a DIN rail, close the DIN rail latch. Press the DIN rail
mounting area of the module against the DIN rail. The latch will momentarily open and lock
into place.
TIP
The 1762 expansion I/O may be mounted horizontally only.
ATTENTION
During panel or DIN rail mounting of all devices, be sure that all debris
(metal chips, wire strands, etc.) is kept from falling into the module.
Debris that falls into the module could cause damage when power is
applied to the module.
Side Side
Top
Bottom
MicroLogix 1200
1762 I/O 1762 I/O 1762 I/O

6MicroLogix 1200 RTD/Resistance Input Module
Publication 1762-IN014B-EN-P - July 2013
Use DIN rail end anchors (Allen-Bradley part number 1492-EA35 or 1492-EAH35) for
environments with vibration or shock concerns.
Panel Mounting
Use the dimensional template shown below to mount the module. The preferred mounting
method is to use two M4 or #8 panhead screws per module. M3.5 or #6 panhead screws may also
be used, but a washer may be needed to ensure a good ground contact. Mounting screws are
required on every module.
TIP
For environments with extreme vibration and shock concerns, use the
panel mounting method described below, instead of DIN rail
mounting.
End Anchor
End Anchor
90
(3.54)
100
(3.94)
40.4
(1.59)
40.4
(1.59)
14.5
(0.57)
For more than two modules: (number of modules - 1) x 40.4 mm (1.59 in.)
NOTE:
Hole spacing tolerance: ±0.4 mm (0.016 in.).
1762 I/O
1762 I/O
1762 I/O
MicroLogix 1200

MicroLogix 1200 RTD/Resistance Input Module 7
Publication 1762-IN014B-EN-P - July 2013
Field Wiring Connections
Grounding the Module
This product is intended to be mounted to a well-grounded mounting surface such as a metal
panel. Additional grounding connections from the module’s mounting tabs or DIN rail (if used)
are not required unless the mounting surface cannot be grounded. Refer to Industrial
Automation Wiring and Grounding Guidelines, Allen-Bradley publication 1770-4.1, for
additional information.
System Wiring Guidelines
Consider the following when wiring your system:
•Do not use the module’s NC terminals as connection points.
•Use Belden shielded, twisted-pair wire to ensure proper operation and high immunity to
electrical noise. See “RTD Wiring Considerations”.
•To limit noise, locate RTD and resistance device signal wires as far away as possible from
power lines, load lines, and other sources of electrical noise, such as hard-contact
switches, relays, and AC motor drives.
•Locate RTD modules away from other modules which generate a significant amount of
heat.
•Under normal conditions, the drain wire and shield junction should be connected to
earth ground, via a panel or DIN rail mounting screw at the 1762-IR4 module end.
•Keep shield connection to ground as short as possible.
•To ensure optimum accuracy, limit overall cable impedance by keeping your cable as
short as possible. Locate the I/O system as close to your sensors or actuators as your
application will permit. See the table on the following page.
Terminal Block Layout
EXC 2
SENSE 2
RTN 2
EXC 3
SENSE 3
RTN 3
EXC 0
SENSE 0
RTN 0
EXC 1
SENSE 1
RTN 1
NC
NC
NC
NC
NC
NC
NC terminals are not intended for
use as connection points.
Do not connect any wires to the NC
terminals.

8MicroLogix 1200 RTD/Resistance Input Module
Publication 1762-IN014B-EN-P - July 2013
RTD Wiring Considerations
Since the operating principle of the RTD module is based on the measurement of resistance, take
special care when selecting your input cable. For 2-wire or 3-wire configurations, select a cable
that has a consistent impedance throughout its entire length.
When using a 3-wire configuration, the module compensates for resistance error due to lead wire
length. For example, in a 3-wire configuration, the module reads the resistance due to the length
of one of the wires and assumes that the resistance of the other wire is equal. If the resistances of
the individual lead wires are much different, an error may exist. The closer the resistance values
are to each other, the greater the amount of error is eliminated.
To insure that the lead values match as closely as possible:
•Keep lead resistance as small as possible and less than 25Ω .
•Use quality cable that has a small tolerance impedance rating.
•Use a heavy-gauge lead wire which has less resistance per foot.
Configuration Recommended Cable
2-wire Belden™ 9501 or equivalent
3-wire — less than 30.48 m (100ft.) Belden™ 9533 or equivalent
3-wire — greater than 30.48 m (100 ft.) or high humidity conditions Belden™ 83503 or equivalent
IMPORTANT
The RTD module requires three wires to compensate for lead resistance
error. We recommend that you do not use 2-wire RTDs if long cable runs
are required, as it reduces the accuracy of the system. However, if a
two-wire configuration is required, reduce the effect of the lead wire
resistance by using a lower gauge wire for the cable (for example, use
AWG #16 instead of AWG #24). The module’s terminal block accepts
two AWG #14 gauge wires.
IMPORTANT
To ensure temperature or resistance value accuracy, the resistance
difference of the cable lead wires must be equal to or less than 0.01Ω .

MicroLogix 1200 RTD/Resistance Input Module 9
Publication 1762-IN014B-EN-P - July 2013
RTD Wiring Configurations
For a 3-wire configuration, the module can compensate for a maximum cable length associated
with an overall cable impedance of 25 ohms.
Three configurations of RTDs can be connected to the 1762-IR4 module:
•2-wire RTD, which is composed of an RTD EXC (excitation) lead wire and a RTN
(return) lead wire
•3-wire RTD, which is composed of a Sense and 2 RTD lead wires
(RTD EXC and RTN)
•4-wire RTD, which is composed of a Sense and 2 RTD lead wires
(RTD EXC and RTN). The second sense wire of a 4-wire RTD is left open.
2-Wire RTD Configuration
IMPORTANT
Using 2-wire configurations does not permit the module to compensate for
resistance error to do lead wire length. The resulting analog data includes
the effect of this uncompensated lead wire resistance. The module
continues to place the uncompensated analog data in the input data file, but
the open-circuit status bit (OCx) is set in word 4 of the input data file for
any enabled channel using a 2-wire configuration. These status bits may be
used in the control program to indicate that the analog data includes error
due to uncompensated lead wires. See page 16 for a detailed discussion of
the open-circuit status bits.
EXC 2
SENSE 2
RTN 2
NC
Belden 9501 Shielded Cable
Cable Shield (to Ground)
RTD EXC
Return
RTD EXC
Return

10 MicroLogix 1200 RTD/Resistance Input Module
Publication 1762-IN014B-EN-P - July 2013
3-Wire RTD Configuration
4-Wire RTD Configuration
Wiring Resistance Devices (Potentiometers)
Potentiometer wiring requires the same type of cable as that for the RTD described on page 8.
Potentiometers can be connected to the module as a 2-wire or 3-wire connection as shown on
page 11.
EXC 2
SENSE 2
RTN 2
NC
Belden 83503 or 9533 Shielded Cable
Cable Shield (to Ground)
RTD EXC
Sense
RTD EXC
Return
Sense
Return
EXC 2
SENSE 2
RTN 2
NC
Belden 83503 or 9533 Shielded Cable
Leave one sensor wire open.
Cable Shield (to Ground)
RTD EXC
Return
RTD EXC
Return
Sense Sense