1734-IT2I — POINT I/O 2-Channel Isolated Thermocouple Input Module

The 1734-IT2I is a two-channel thermocouple input module for the 1734 POINT I/O platform. Both channels accept standard thermocouple types (J, K, T, E, R, S, B) and report calibrated temperature readings in degrees Celsius or Fahrenheit directly to the controller, with built-in cold junction compensation handled on the module. The "I" suffix means the channels are individually isolated from each other and from the POINT I/O backplane — neither channel shares a reference with the other or with the control system ground.

Two channels is often exactly the right count for localized temperature monitoring at a POINT I/O node — one process thermocouple and one reference or safety thermocouple, a motor winding and bearing temperature pair, or inlet and outlet temperatures on a heat exchanger section. The individual channel isolation makes it straightforward to connect thermocouples from physically separate equipment with different ground references without creating measurement errors from ground loops.

Specifications

Parameter	Value
Part Number	1734-IT2I
Platform	POINT I/O (1734)
Input Channels	2 (individually isolated)
Thermocouple Types	J, K, T, E, R, S, B
Temperature Range (Type K)	−200°C to +1370°C
Temperature Range (Type J)	−210°C to +760°C
Temperature Range (Type T)	−200°C to +400°C
Resolution	0.1°C
Accuracy	±1°C typical @ 25°C ambient
Cold Junction Compensation	Internal, automatic
Channel Isolation	Channel-to-channel and channel-to-backplane
Isolation Voltage	250V AC continuous
Open-Circuit Detection	Yes (upscale or downscale configurable)
Backplane Current (5V)	100 mA
Operating Temperature	−20°C to 55°C
Standards	UL 508, CE, IEC 61131-2

Thermocouple Types and Accuracy

The module supports seven IEC standard thermocouple types. Selecting the right type for an application depends on temperature range, accuracy requirements, and the environment:

Type K (Chromel/Alumel) — the most versatile general-purpose choice. Wide range (up to 1370°C), good linearity across mid-range temperatures, and widely available. Used in furnaces, industrial ovens, and general process temperature measurement.
Type J (Iron/Constantan) — common in older equipment and food processing applications. Lower maximum temperature than K, but slightly better sensitivity in the 0–400°C range. Avoid in humid environments — the iron conductor corrodes.
Type T (Copper/Constantan) — the best choice for cryogenic and sub-zero applications. Accurate and stable below 0°C where K and J performance degrades. Common in refrigeration, cold storage, and laboratory systems.
Types R, S (Platinum/Rhodium) — high-accuracy, high-temperature types for metallurgical and glass furnace applications. Expensive and fragile; only justified where the temperature range or accuracy requirement demands them.
Type B — extreme temperatures up to 1820°C. Used in the most demanding high-temperature industrial processes.

The module's ±1°C typical accuracy applies to the signal conditioning and cold junction compensation electronics. The overall system accuracy also depends on the thermocouple's own calibration tolerance — standard tolerances for Type K are ±2.2°C or ±0.75%, whichever is greater. For critical measurements, use Special Limits of Error (SLE) thermocouples which offer ±1.1°C or ±0.4%.

FAQ

Q: Can the module detect a broken or disconnected thermocouple?

Yes. Open-circuit detection is built in. When a thermocouple wire breaks or disconnects, the channel drives to either full upscale or full downscale (configurable in the module properties). The controller program can monitor for this out-of-range condition to trigger an alarm.

Q: Can the two channels measure different thermocouple types simultaneously?

Yes. Each channel is configured independently in Studio 5000 — channel 0 can be Type K while channel 1 is Type T, or any other combination from the supported types.

Q: How long can the thermocouple extension wire be between the junction and the module?

Thermocouple extension wire must be used — not standard copper wire — to avoid introducing additional thermoelectric junctions that generate spurious voltages. Extension wire runs of 30–60 m are common without significant accuracy degradation, provided the wire is properly shielded and routed away from noise sources. Use the correct extension wire type for the thermocouple type (Type K extension wire for Type K thermocouples, etc.).

Q: What POINT I/O adapters is the 1734-IT2I compatible with?

All standard 1734 adapters are compatible — EtherNet/IP (1734-AENT), DeviceNet (1734-ADN), ControlNet (1734-ACN), and others. The thermocouple module communicates via the POINT I/O backplane and is independent of network protocol.

Q: The accuracy spec is ±1°C — does that apply across the full temperature range?

The ±1°C figure is the module electronics accuracy at 25°C ambient. At extreme temperatures (near the top of a thermocouple's range) and at ambient temperatures away from 25°C, total system accuracy is higher due to the thermocouple's own non-linearity and the temperature coefficient of the module's electronics. For applications requiring tighter accuracy at specific temperature ranges, check the full accuracy specification across the operating temperature and input range.

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