Technical data
Publication 1794-2.1 - January 2000
128 24V dc Thermocouple/RTD Input Module Cat. No. 1794-IRT8 FLEX I/O and FLEX Integra Product Data
Specifications - 1794-IRT8
Number of Inputs 8 Channels (2 groups of 4)
Module Location Cat. No. 1794-TB3G, -TB3GS Terminal Base Unit
Nominal Input Ranges -40 to +100mV dc for thermocouples
0 to 325mV dc for RTDs
0 to 500 Ω for resistance range
Supported RTD Types Resistance:
100 Ω Pt ∝ = 0.00385 Euro (-200 to +870
o
C)
100 Ω Pt ∝ = 0.003916 U.S. (-200 to +630
o
C)
200 Ω Pt ∝ = 0.00385 Euro (-200 to +400
o
C)
200 Ω Pt ∝ = 0.003916 U.S. (-200 to +400
o
C)
100 Ω Nickel ∝ = 0.00618 (-60 to +250
o
C)
120 Ω Nickel ∝ = 0.00672 (-80 to +320
o
C)
200 Ω Nickel ∝ = 0.00618 (-60 to +200
o
C)
10 Ω Copper ∝ = 0.00427 (-200 to +260
o
C)
Supported Thermocouple
Types
Type B: 300 to 1800
o
C (572 to 3272
o
F)
Type E: -270 to 1000
o
C (-454 to 1832
o
F)
Type J: -210 to 1200
o
C (-346 to 2192
o
F)
Type K: -270 to 1372
o
C (-454 to 2502
o
F)
Type TXK/XK (L):-200 to 800
o
C (-328 to 1472
o
F)
Type N: -270 to 1300
o
C (-454 to 2372
o
F)
Type R: -50 to 1768
o
C (-58 to 3214
o
F)
Type S: -50 to 1768
o
C (-58 to 3214
o
F)
Type T: -270 to 400
o
C (-454 to 752
o
F)
Resolution 14 bits
Data Format
o
C (implied decimal point XXX.X)
o
F (implied decimal point XXX.X)
o
K (implied decimal point XXX.X)
-32767 to +32767
0-65535
0-5000 (Ω mode) (implied decimal point XXX.X)
-4000 to +10000 (millivolt mode) (implied decimal
point XXX.XX)
Accuracy vs. Filter Cutoff 0.05% of full range in millivolt mode with filtering
selected
Hardware only = 0.10% of full range in millivolt
mode
Common Mode Rejection -80db @ 5V peak-to-peak 50-60Hz
Common Mode Input Range ±4V minimum
Isolation Voltage 1500V ac (rms) or 2550V dc for 1.0s between
customer and system
System Throughput
- add 0.5ms if filtering is
selected
For maximum throughput short circuit all unused
channels.
5.4ms - millivolt
7.05ms -Ω- 2-wire RTD
9.1ms -Ω- 3-wire RTD
9.2ms -Ω- 4-wire RTD
7.3ms - 2-wire RTD (
o
F)
9.4ms - 4-wire RTD (
o
F)
7.7ms - 2-wire RTD (
o
C), (
o
K)
9.8ms - 4-wire RTD (
o
C), (
o
K)
9.35ms - 3-wire RTD (
o
F)
9.75ms - 3-wire RTD (
o
C), (
o
K)
6.65ms - Thermocouples (
o
F)
7.0ms - Thermocouples (
o
C), (
o
K)
Open Circuit Detection Defaults to maximum value
Specifications - 1794-IRT8 (continued)
Excitation Current 630µA
Open Input Detection Time 0 to 3.8s for revision D or earlier
Immediate detection (maximum 1 scan) for
revision E or later
Overvoltage Capability
7V dc continuous @ 25
o
C
RFI Immunity Error of less than 1% of range at 10V/M
27 to 1000MHz
Overall Drift
with Temperature
150ppm/
o
C of span (maximum)
Cold Junction Compensation
Range
0 to 70
o
C
Cold Junction Compensator A-B Cold Junction Compensator Kit, 1794-CJC2
(kit supplied with the module and contains 2
compensators)
Indicators 1 green power status indicator
Flexbus Current 40mA
Power Dissipation 3W maximum @ 31.2V dc
Thermal Dissipation Maximum 10.2 BTU/hr @ 31.2V dc
Keyswitch Position 3
General Specifications
External dc Power
Supply Voltage
Voltage Range
Supply Current
24V dc nominal
19.2 to 31.2V dc (includes 5% ac ripple)
85mA @ 24V dc
Dimensions HxWxD 46mm x 94mm x 53mm (1.8in x 3.7in x 2.1in)
Environmental Conditions
Operational Temperature
Storage Temperature
Relative Humidity
Shock Operating
Non-operating
Vibration
0 to 55
o
C (32 to 131
o
F)
-40 to 85
o
C (-40 to 185
o
F)
5 to 95% noncondensing (operating)
5 to 80% noncondensing (non-operating)
30g peak acceleration, 11(±1)ms pulse width
50g peak acceleration, 11(±1)ms pulse width
Tested 5g @ 10-500Hz per IEC 68-2-6
Conductors
Thermocouple
mV
Category
Use appropriate shielded thermocouple wire
1
Belden 8761
2
2
Publications
Installation Instructions
User Manual
1794-5.50
1794-6.5.12
Agency Certification
1 Refer to thermocouple manufacturer for proper thermocouple extension.
2 Use this conductor category information for planning conductor routing. Refer to
publication 1770-4.1, “Industrial Wiring and Grounding Guidelines for Noise Immunity.”
Class I Division 2 certified
Groups A, B, C, D certified
Class I Zone 2 Group IIC certified