Specifications

23
SLC 500 Programmable Controllers and I/O Modules
1746-NR4 and -NR8 RTD Resistance Input Modules
Features
These modules provide a choice of four filter frequencies, permitting you to select input noise filtering
appropriate to the application and surrounding environment. Either or both 50Hz and 60Hz noise can be
filtered from the input signal for greater noise rejection and resolution. For applications where system
response speed is critical, minimum filtering can be selected to reduce the time it takes a step change
at the input to be made available to the SLC 500 controller.
These modules require no user calibration. The 1746-NR4 module’s channels initiate a calibration cycle
at power-up, on channel configuration, or on your command to compensate for module component drift.
The 1746-NR8 initiates a calibration cycle at power-up or at user-enabled periodic intervals (default =
every 5 minutes). This enhances module accuracy and saves valuable service time and money.
Provides fault diagnostics to check for open circuits, short circuits or out-of-range values, then indicates operational problems on
status LEDs. Channel status LEDs and diagnostic bits signal you if input channel data is out of range or if an open-circuit or short-
circuit condition is present. Channel configuration validity is also checked. In addition, a module status LED differentiates
recoverable channel errors from more serious module-related problems, saving you troubleshooting time and money.
Specifications
Description 1746-NR4 Specification 1746-NR8 Specification
Backplane Current Draw 50 mA at 5V dc, 50 mA at 24V dc 100 mA at 5V dc, 70 mA at 24V dc
Temperature Scale (Selectable) 1˚C or 1˚F and 0.1˚C or 0.1˚F
Resistance Scale (Selectable) 1Ω or 0.1Ω for all resistance ranges; or 0.1Ω or 0.01Ω for 150Ω potentiometer.
Input Step Response Selectable Filter: Selectable Filter:
• 10 Hz • 28 Hz
• 50 Hz • 50/60 Hz
• 60 Hz • 800 Hz
• 250 Hz • 6400 Hz
RTD Excitation Current Two current values are user-selectable: Two current values are user-selectable:
• 0.5 mA
(1)
0.25 mA
(1)
• 2.0 mA
(2)
1.0 mA
(2)
Open-Circuit or Short-Circuit Method Zero, upscale or downscale
Maximum Cable Impedance 25Ω maximum per 1000 feet
Maximum Wire Size Two 24 AWG wires per terminal One 24 AWG wire per terminal
Calibration Auto-calibration at power-up and Auto-calibration at power-up and
when a channel is enabled user-enabled periodic calibration
Channel-to-Channel Isolation None ±5V
Input-to-Backplane Isolation 500V ac for 1 minute
Common Mode Voltage Separation ±1V maximum
Recommended for use with higher resistance ranges for both RTDs and direct resistance inputs (1000W RTDs and 3000W resistance input).
Contact the RTD manufacturer for recommendations. Cannot use for 10W Copper RTD.
Must use for 10W Copper RTD. Recommended to use for all other RTD and direct resistance inputs, except 1000W RTDs and 3000W resistance input ranges.
Contact RTD manufacturer for recommendations.