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Brand: Allen-Bradley
Allen-Bradley 1756-OF4 ControlLogix 4-Point Analog Output Module
Description
Four voltage or current analog outputs for valves and drives
The Allen-Bradley 1756-OF4 is a four-channel analog output module. Each channel can be configured for voltage output of plus or minus 10 V or current output of 0 to 20 mA, so a single card can drive control valve positioners, variable-speed drive references and analog indicators.
Outputs have 15-bit voltage and 16-bit current resolution and the module settles to 95 percent of its final value in under 2 ms with resistive loads. Floating point or integer data can be used, which lets older programs be migrated without changing the data type. The module is configured in Studio 5000 Logix Designer, where each channel gets its own range, scaling and fault-state behaviour.
Technical specifications
| Parameter | Specification |
|---|---|
| Catalog number | 1756-OF4 (1756-OF4K conformal coated listed separately) |
| Outputs | 4, voltage or current |
| Output ranges | +/-10 V; 0-20 mA |
| Resolution | Voltage 15 bits across 10.5 V (320 uV per bit); current 16 bits across 21 mA (325 nA per bit) |
| Drive capability | Voltage: loads over 2000 Ohm; current: 0 to 750 Ohm |
| Calibrated accuracy | Better than 0.05 percent of range |
| Module error | Voltage 0.1 percent of range; current 0.2 percent |
| Settling time | Under 2 ms to 95 percent with resistive loads |
| Short-circuit protection | Electronically current limited to 21 mA or less |
| Overvoltage protection | +/-24 V DC |
| Open-circuit detection | Current output only (output must be above 0.1 mA) |
| Module scan time | 8 ms integer; 12 ms floating point |
| Data format | Integer (left justified, 2s complement) or IEEE 32-bit floating point |
| Backplane current | 200 mA max at 5.1 V DC; 155 mA max at 24 V DC (4.74 W) |
| Power dissipation | 4.74 to 1.74 W, depending on load 0 to 750 Ohm |
| Isolation | 250 V continuous basic, output channels to backplane; no isolation between channels |
| Operating temperature | 0 to +60 C |
| Non-operating temperature | -40 to +85 C |
| Vibration / shock | 2 g at 10-500 Hz / 30 g operating, 50 g non-operating |
| Slot width / keying | 1 slot; electronic keying, software configurable |
| Enclosure / wire category | Open-style; wire category 1 |
Wiring and loop notes
There is no channel-to-channel isolation, so loops that share a ground should be checked for interaction. Open-circuit detection works only on current outputs and only when the output is above 0.1 mA, so a loop parked at 0 mA will not report a break. The 750 Ohm maximum current-loop resistance covers most positioners and I/P converters but should be checked when long cable or a HART resistor is added.
Selection notes
For eight channels, higher density or HART, Rockwell lists the 1756-OF8 and OF8H, which are separate catalog numbers. Check the series and K suffix on the existing module and keep the removable terminal block in the order. The values come from the manufacturer technical data and should be confirmed for the actual project.
Scan time is 8 ms for integer data or 12 ms for floating point, and settling time is under 2 ms to 95 percent with resistive loads. Voltage outputs drive loads above 2000 Ohm and current outputs drive 0 to 750 Ohm, so check loop resistance of long runs before commissioning.
Documents and quotation
The linked Rockwell Automation technical data covers the full 1756 I/O range (file size about 15 MB, hosted by Rockwell Automation). Related PLC hardware sits in the PLC & I/O Cards category. Send the catalog number and quantity to Seven Star LLC, an independent supplier in Muscat, to obtain a quotation.
Datasheets & Documents
- Technical data Rockwell Automation 1756 ControlLogix I/O Specifications, publication 1756-TD002U (September 2026) Download
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About brand
Allen-Bradley is the brand of Rockwell Automation for industrial control: ControlLogix and CompactLogix controllers, I/O systems, PanelView operator terminals, PowerFlex drives, motor control and industrial network equipment. The company began in Milwaukee in 1903, when Lynde Bradley and Dr. Stanton Allen formed the Compression Rheostat Company to make the motor speed controller Bradley had invented in 1901. It took the name Allen-Bradley in 1909 and was bought by Rockwell International in 1985. Since 2001 its owner has been Rockwell Automation, which is still headquartered in Milwaukee, Wisconsin.
Allen-Bradley company profile
| Founded | 1903, Milwaukee, Wisconsin, USA, as the Compression Rheostat Company |
|---|---|
| Founders | Lynde Bradley (inventor of the compression rheostat, 1901) and Dr. Stanton Allen (investor); Harry Bradley joined in 1904 |
| Name | Allen-Bradley Company from 1909 |
| Ownership | Acquired by Rockwell International in 1985 for about USD 1.65 billion; a brand of Rockwell Automation (NYSE: ROK) since 2001 |
| Headquarters | Milwaukee, Wisconsin, USA |
| Product families | Logix programmable automation controllers (ControlLogix, CompactLogix), legacy SLC 500 and MicroLogix PLCs, Micro800 controllers, POINT, FLEX and Compact I/O, PanelView HMIs, PowerFlex AC drives, contactors, motor starters and soft starters, safety components, Stratix Ethernet switches |
Milestones
- 1901: Lynde Bradley invents the compression rheostat to control the speed of electric motors.
- 1903: The Compression Rheostat Company is formed in Milwaukee with an initial investment of USD 1,000.
- 1904: Harry Bradley joins; a crane controller is shown at the St. Louis World's Fair.
- 1909: The company is renamed Allen-Bradley.
- 1985: Rockwell International acquires Allen-Bradley.
- 2001: Rockwell Automation becomes the company's name; the Allen-Bradley brand marks 100 years in 2003.
Reading Allen-Bradley catalogue numbers
The first digits of an Allen-Bradley catalogue number identify the platform, which tells you what is compatible with what. 1756 is ControlLogix (chassis-based, used for large process and plant control), 1769 is CompactLogix 5370 with Compact I/O, 5069 is CompactLogix 5380 with Compact 5000 I/O, 1734 is POINT I/O, 1794 and 5094 are FLEX and FLEX 5000 distributed I/O, 1746 and 1747 belong to the older SLC 500 family, 1766 is MicroLogix 1400 and 2080 is Micro800. For drives, 25B is PowerFlex 525 and 22B is PowerFlex 40; in a code such as 25B-D010N114, "D" means 380–480 V, "010" is the output current rating, and N114 instead of N104 means the drive has an integrated EMC filter. Many plants in the region still run SLC 500 and older MicroLogix systems, which Rockwell has discontinued, so exact spares and migration to CompactLogix are both common requests.
Where Allen-Bradley products are used
In Oman and the GCC, Allen-Bradley controllers and drives run on oil and gas facilities, water treatment and pumping stations, cement, food and beverage and packaging plants, and on machines supplied by American OEMs. ControlLogix is often the platform for plant control systems, while PowerFlex drives are used on pumps, fans and conveyors.
Allen-Bradley products we list
| Family | Examples |
|---|---|
| ControlLogix | 1756-L85E, 1756-EN2T, 1756-EN2TR, 1756-IF16, 1756-IB32, 1756-PA75, 1756-A10 |
| CompactLogix and Micro controllers | 5069-L320ER, 5069-L340ERM, 1769-L33ER, 1769-L16ER, MicroLogix 1400, Micro820, SLC 500 (1746) |
| Distributed I/O | 1734-AENTR, 1734-IB8, 1734-IE2C, 1734-IB8S safety, 1794-AENTR, 5094-AENTR, 5069-IF8 |
| Operator terminals | PanelView Plus 7 10-inch, PanelView Plus 7 15-inch, PanelView 800, PanelView 5310 |
| Drives, motor control and networking | PowerFlex 525, PowerFlex 755, PowerFlex 4, 150-A180NBD SMC, Stratix 2000, 1783-NATR |
Ordering Allen-Bradley products: what we need
Send the full catalogue number and the series letter from the label (for example 1756-EN2T Series D), because firmware and compatibility can change between series. For drives, add the motor power, voltage and filter option. For a discontinued SLC 500 or MicroLogix part, tell us whether you need the exact spare or a migration proposal.
Facts checked against Rockwell Automation's published company history, October 2026.
Browse Allen-Bradley products by category: PLC & I/O Cards, AC Drives.
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Frequently Asked Questions
How many outputs does the 1756-OF4 have?
Four channels, each voltage or current.
What are the output ranges?
+/-10 V and 0-20 mA.
What load can a current output drive?
0 to 750 Ohm.
Is there channel isolation?
No, only output to backplane isolation is listed.
How fast does it settle?
Within 2 ms to 95 percent of final value with resistive loads.
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