Allen-Bradley 1734-OE2C POINT I/O 2-Channel Analog Current Output Module

Two 4-20 mA outputs on a single POINT I/O slot

The Allen-Bradley 1734-OE2C is a POINT I/O analog output module with two current outputs. Each channel can be configured for 4 to 20 mA or 0 to 20 mA and drives loads such as valve positioners, current-to-pneumatic converters, chart recorders and variable-speed drive references. The module outputs 0 mA until communication has been established, which is a safe default for most loops.

It shares a housing with the voltage version, 1734-OE2V, and the installation sheet covers both. This page concerns the current version only; the C in the catalog number identifies current.

Technical specifications

Performance that matters when you size the loop

The sheet lists a resolution of 13 bits over 0 to 21 mA, around 2.5 microamps per count, an absolute accuracy of 0.1% of full scale at 25 °C and a drift of 30 ppm per degree Celsius. Conversion is by digital-to-analog converter at 16 microseconds, with a 24 microsecond step response to 63% of full scale.

The compliance of each channel covers loads from 0 to 750 ohm. Add up the loop resistance of the field cable and the receiving device before choosing it for a long run. The outputs are single-ended and non-isolated from each other, so do not use them where independent isolation between channels is required.

Power, mounting and keying

The module needs external 24V DC field power (10 to 28.8V DC range) with a supply current of 70 mA including both outputs at 20 mA, plus 75 mA from POINTBus at 5V DC. Power dissipation is 1.23 W with 750 ohm loads and 1.83 W with 0 ohm loads. It mounts on a 1734-TB, 1734-TBS, 1734-TOP or 1734-TOPS family base, with the keyswitch set to position 4.

Wire with shielded copper, 22 to 14 AWG, rated at 75 °C or higher. The status indicators show module, network and output status for each channel. The family is certified for Class I Division 2 and for Zone 2 ATEX and IECEx as listed in the sheet; confirm the marks on the module you receive.

Key features of the 1734-OE2C

• Two current output channels, each configurable for 4–20 mA or 0–20 mA.
• 13-bit resolution over 0–21 mA and 0.1 % of full scale absolute accuracy at 25 °C.
• Loads up to 750 ohm per channel.
• Fast 16 µs conversion for responsive control loops.
• Outputs held at 0 mA until communication is established.
• Narrow 12.1 mm module on removable POINT I/O terminal bases.

Checking the load and loop resistance

The module can drive a total loop resistance of up to 750 ohm. This includes the input resistance of the receiving device and the resistance of both cable conductors. For a long cable run to a valve positioner or a remote indicator, add up the device input resistance, the cable resistance and any barriers or isolators in the loop. If the total exceeds 750 ohm, the output will not reach 20 mA. Note that the outputs are non-isolated; where the receiving devices are on different earths, a signal isolator may be needed.

Fault and idle behaviour

In POINT I/O, the behaviour of outputs on communication fault or program mode is configured in the module properties in the controller project. Decide whether each channel should hold its last value or go to a defined safe value, and document this in the control philosophy, especially for valves and drive references.

Building a POINT I/O node

The module is installed on a terminal base on DIN rail, next to the communication adapter (for example an EtherNet/IP or DeviceNet adapter) and other POINT I/O modules. The 24 V DC field power is distributed along the backplane, and the POINTBus current (75 mA for this module) must be included in the adapter’s current budget. The mechanical keyswitch on the base should be set to position 4 so that only an appropriate module can be fitted.

Use in Oman and GCC plants

Typical applications are oil and gas skids, water treatment and HVAC systems where a PLC sends setpoints to control valves and drives. For panels exposed to humidity, salty coastal air or corrosive gases, the conformal coated version 1734-OE2CK is worth considering. Keep the panel temperature within the Rockwell specification by providing ventilation or cooling where needed.

What to include in your RFQ

State the catalog number 1734-OE2C (or 1734-OE2CK for the coated version), the quantity, and any terminal bases you need such as 1734-TB or 1734-TOP. Also give the delivery location and the required date.

Commissioning checklist

Before handing over the loop, force each channel to 4, 12 and 20 mA from the controller and measure the current with a calibrated meter at the field device. Confirm that the valve or drive responds over its full range, and record the results in the loop check sheet.

Documents and quotation

The manufacturer installation sheet 1734-IN002 gives the output table, wiring diagram and certification page. For a quotation, send the 1734-OE2C reference, series, quantity, the controller or adapter and the loads on each channel. See PLC & I/O Cards for related hardware.