Specifications

Publication 1794-SG002D-EN-P - May 2012
Select FLEX I/O Modules 43
1794-IR8 RTD Input Module
The 1794-IR8 is a temperature-measuring module that accepts 2- and 3-wire
RTDs. use the 1794-IR8 in applications where channel fast-update rate is not
required. If you need channel fast-update rates, use the 1794-IRT8 module
described on page 44.
RTD Input Module
Specification 1794-IR8
Input resolution 16 bits across 435 Ω
Sensors supported Resistance:
100 Ω Pt μ = 0.00385 Euro (-200…870 °C)
100 Ω Pt μ = 0.003916 U.S. (-200…630 °C)
200 Ω Pt μ = 0.00385 Euro (-200…630 °C)
500 Ω Pt μ = 0.00385 U.S. (-200…630 °C)
100 Ω Nickel μ = 0.00618 (-60…250 °C)
120 Ω Nickel μ = 0.00672 (-60…250 °C)
200 Ω Nickel μ = 0.00618 (-60…250 °C)
500 Ω Nickel μ = 0.00618 (-60…250 °C)
10 Ω Copper μ = 0.00427 (-200…260 °C)
Data format 16 bits, 2’s complement, left justified;
Offset binary
Settling time 100% of final value available at system throughput rate
Normal mode rejection ratio 60 dB @ 60 Hz for A/D filter cutoff @ 15 Hz
Common mode rejection ratio -120 db @ 60 Hz
-100 dB @ 50 Hz with A/D filter cutoff @ 10 Hz
Common mode voltage 0V between channels (common return)
Accuracy, normal mode (max)
(1)
(1) The number is based on the hardware of the module only. Additional errors are introduced depending on the
sensor used., environment, and other factors. Contact technical support for more information.
0.05% Full Scale (low humidity) without calibration
Accuracy, enhanced mode (typical) 0.01% Full Scale (low humidity) without calibration
System throughput, normal mode Programmable from 28…325 ms/channel
325 ms (1 channel scanned)
2.6 s (8 channels scanned)
System throughput, enhanced mode Programmable from 56…650 ms/channel
650 ms (1 channel scanned)
2.925 s (8 channels scanned)
Open RTD detection Out of range upscale reading
Open circuit detection type Available at system throughput rate
Overvoltage capability 35V DC, 25V AC continuous @ 25 °C
250V peak transient
Channel bandwidth DC to 2.62 Hz (-3 dB)
RTD excitation current 718.39 μA
RFI immunity Error of <1% of range @ 10V/m, 27…1000 MHz
Gain drift with temperature Normal mode: 20 ppm/ °C max
Enhanced mode: 10 ppm/ °C max
Dimensions (HxWxD), approx 46 x 94 x 53 mm (1.8 x 3.7 x 2.1 in.)
94 x 94 x 69 mm (3.7 x 3.7 x 2.7 in.) installed
Temperature, operating 0…55 °C (32…131 °F)