Application Scenarios
Consider a pharmaceutical API reaction suite where six jacketed reactors each carry a Pt100 RTD immersed in the product. The reactors share a common utility skid, but the product-side sensing elements are grounded through their thermowell welds to different vessel bodies — and each vessel body sits at a slightly different electrical potential because of cleaning-in-place piping and agitator drive grounds. On a non-isolated RTD module, these small ground-potential differences would circulate common-mode current through the sensor leads, corrupting readings and triggering nuisance “out-of-range” faults at exactly the moment a batch is reaching its critical holding temperature.
This is the precise problem that the Allen-Bradley 1756-IR6I was engineered to eliminate. Because each of the six RTD channels is independently isolated, the module tolerates these per-vessel ground-potential differences without common-mode current circulating, and the 120 dB common-mode noise rejection at 60 Hz (100 dB at 50 Hz) strips out the inverter-driven heater noise that rides on the same cable tray as the sensor runsemacstores.com. Combined with the module’s open-circuit detection — which drives the reading to negative full scale within 5 seconds on any lost wire — the 1756-IR6I delivers regulatory-compliant, batch-record-grade temperature data on the most demanding multi-vessel installations without the external signal isolators and marshalling cabinets that a non-isolated alternative would require.
Parameter
| Main Parameters | Value / Description |
|---|---|
| Product Model | 1756-IR6I |
| Manufacturer | Rockwell Automation / Allen-Bradley (USA) |
| Product Category | Isolated RTD Analog Input Module (ControlLogix 1756 series) |
| Number of Inputs | 6, individually isolated RTD channels |
| Input Ranges | 1–487 Ω, 2–1000 Ω, 4–2000 Ω, 8–4020 Ω (resistance) |
| Resolution | 16 bits — 7.7 mΩ/bit (1–487 Ω) · 15 mΩ/bit (2–1000 Ω) · 30 mΩ/bit (4–2000 Ω) · 60 mΩ/bit (8–4020 Ω) |
| Supported Sensors | Pt100/200/500/1000 (α=385 & 3916), Ni120 & Ni100/120/200/500 (α=672 & 618), Cu 10 Ω; 2-, 3-, or 4-wire |
| Calibration Accuracy | Better than 0.1% of range @ 25 °C; module error 0.54% of range |
| Conversion Method | Sigma-Delta, 15 Hz channel bandwidth, <80 ms settling to 5% FS |
| Noise Rejection | NMR 60 dB @ 60 Hz; CMR 120 dB @ 60 Hz, 100 dB @ 50 Hz |
| Isolation Voltage | 250 V continuous (basic insulation), channel-to-backplane and channel-to-channel; routine-tested at 1350 V AC / 2 s |
| Backplane Draw | 250 mA @ 5.1 Vdc + 125 mA @ 24 Vdc; 4.25 W total, 4.3 W max dissipation |
| Operating Temperature | 0…60 °C (32…140 °F); storage –40…+85 °C; humidity 5–95% non-condensing |
| Overvoltage Protection | 24 V AC/DC maximum on signal terminals |
| Slot / RTB | 1 slot width; 1756-TBNH or 1756-TBSH removable terminal block, 20-pin |
| Certifications | UL Listed, CSA Certified (incl. Class I Div 2 Groups A,B,C,D), CE (EMC + LVD), C-Tick, ATEX Ex nA IIC T4 X Gc, FM Class I Div 2, KC |
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