The Allen-Bradley 1762-OF4, also cataloged as the 1762 analog output module, operates as a dedicated hardware component for converting Logix-backplane digital words into 0-10 VDC or 4-20 mA field signals within MicroLogix 1200 local expansion racks.

Catalog Number Decoding

• 1762-: MicroLogix 1200 expansion I/O family
• OF: Analog Output module type
• 4: 4 single-ended output channels

Hardware Specifications

Backplane Bus Latency and Firmware Flash Notes

The 1762-OF4 attaches to a MicroLogix 1200 CPU (1762-Lxx) or 1762-L24/L40 base via the right-side expansion connector. Data exchange uses the 1762 proprietary 8-bit parallel backplane protocol; update rate per output word is 1 scan of the "OW" data file, no deterministic timestamping. Firmware is mask-ROM fixed; no flash update path exists on this module class. I/O density scaling is limited to 8 modules per CPU string including mixed 1762-I/O; exceeding 8 drops the 9th node offline with no bus retry. Channel-to-channel isolation is not provided—all 4 outputs share a common internal 24 VDC return; external galvanic isolation must be field-added for hazardous loops.

Ordering Info

• 1 x 1762-OF4 4-channel analog output module
• 1 x Removable terminal block (pre-fitted)
• 2 x DIN rail retention clips

DIN Rail and Wiring Rules

• Snap onto 35 mm DIN rail (EN 60715) or secure with 2 x M4 panel screws, torque 0.8 N·m.
• Use 0.2-1.5 mm² stranded wire with ferrules; strip length 6 mm.
• Separate analog output pairs from 24 VDC power and relay wiring by 50 mm or run in separate conduit.
• Ground module mounting rail to panel ground bus with 2.5 mm² green/yellow conductor.
• Do not land 4-20 mA loop field power on module terminals; sink/source compliance is internal 24 VDC backplane only.

Frequently Asked Questions

Q: Can the 1762-OF4 be hot-swapped on a powered MicroLogix 1200 rack?

A: No. The 1762 expansion bus has no staged power insertion. Removing or inserting under 24 VDC backplane power arcs the ribbon connector and forces CPU fault code 0015h. De-energize before swap.

Q: What is the backplane current load drawn from the CPU?

A: 90 mA at 24 VDC nominal. A 1762-L40 CPU supplies max 450 mA to expansion; fitting 5 x 1762-OF4 leaves 0 mA headroom and trips bus undervoltage.

Q: Are the 4 analog outputs electrically isolated from each other?

A: No. All channels share a common internal 0 V reference tied to backplane 24 VDC return. Differential loops require external isolators; channel crosstalk is 0.1% typical without isolation.

Q: Can output type be mixed per channel (e.g. ch1 voltage, ch2 current)?

A: No. Output mode is global per module, set by DIP switch block SW1 on the side: all 4 channels are 0-10 VDC or all 4 are 4-20 mA. Per-channel mixing requires two modules.

Q: What D/A resolution applies to the 4-20 mA range?

A: 14-bit monotonic. 4 mA = 0 counts, 20 mA = 16383 counts. Step size is 0.00098 mA; full-scale 21 mA clamps at 16383 with no overflow fault.

Q: Does the module support HART signal superimposition on 4-20 mA?

A: No. The 1762-OF4 uses a passive sinking output stage with 24 VDC internal compliance. HART modem injection requires external 250 ohm shunt and isolator, not native.

Q: Minimum scan impact when writing OW data file?

A: One ladder scan writes the OWx:y word to D/A latch. If CPU scan is 4 ms, output refresh latency is 4 ms max. Faster update needs 1769-OF4 on CompactLogix, not 1762.

Q: What happens if 24 VDC backplane sags below 20 VDC?

A: D/A reference collapses; outputs drift linearly. At 18 VDC the module faults on bus undervoltage, outputs drive to 0 V / 4 mA fail-low until 21 VDC restore hysteresis clears.