1769-OF2 — Compact I/O 2-Channel Analog Output Module

The 1769-OF2 is a two-channel analog output module for the 1769 Compact I/O platform. Each channel outputs either a voltage signal (0–10V or ±10V) or a current signal (0–20 mA or 4–20 mA), configured independently per channel in the module properties. Resolution is 12-bit, and the channels share a common reference — they are not isolated from each other or from the backplane ground.

Two analog output channels is often exactly what a compact machine controller needs. A PID loop controlling a valve position, a second channel setting a drive speed reference — common automation tasks that don't require a full 4 or 8-channel analog output module. The 1769-OF2 covers these applications in a single Compact I/O slot without consuming more I/O capacity than the machine actually needs.

Specifications

Parameter	Value
Part Number	1769-OF2
Platform	Compact I/O (1769)
Output Channels	2
Voltage Output Ranges	0–10V DC, ±10V DC
Current Output Range	0–20 mA, 4–20 mA
Resolution	12-bit (over full output range)
Voltage Output Accuracy	±0.5% of full scale @ 25°C
Current Output Accuracy	±0.5% of full scale @ 25°C
Min Load (voltage mode)	1 kΩ
Max Load (current mode)	500 Ω @ 24V field supply
Isolation	Not isolated (channels share common with backplane)
External Supply Required	Yes — 24V DC (for current output mode)
Backplane Current (5V)	60 mA
Operating Temperature	0°C to 60°C
Standards	UL 508, CE, IEC 61131-2

Voltage vs. Current Output — Choosing the Right Mode

The choice between voltage and current output comes down to cable length, noise environment, and what the receiving device accepts. Voltage outputs are simpler to wire — just connect positive and negative — but the signal is susceptible to resistive drops along the cable (which shift the received value) and to induced noise from adjacent wiring. For short runs in a single panel, voltage output works cleanly.

Current output (particularly 4–20 mA) is more robust over distance. The current level in the loop is the same at both ends regardless of cable resistance (as long as the loop supply has sufficient voltage headroom), and current loops reject inductively coupled noise more effectively than voltage signals. For runs longer than a few meters, or for connections to drives and instruments in electrically noisy environments, current output is the better choice.

The 4 mA live-zero of the 4–20 mA range also provides an open-circuit alarm — the receiving device sees below 4 mA and knows something is wrong, rather than misreading a broken wire as a zero setpoint.

Where These Two Channels Get Used

With only two outputs, applications tend to be specific and purposeful rather than general:

One channel for a PID-controlled valve position, one for a PID-controlled pump speed — a small process loop with two manipulated variables sharing one module.
Both channels as speed references to two independent variable-speed drives on a coordinated machine, where the ratio between the two speeds is controlled in software.
One channel as a setpoint signal to a temperature controller, the second to a proportional heating valve — common in small thermal processing systems.
One channel driving an electro-pneumatic pressure regulator, the second providing a 0–10V reference to an HMI display for operator-entered setpoints fed back to a secondary loop.

FAQ

Q: Does the external 24V supply need to be isolated from the controller's 24V supply?

Since the module's channels share a common with the backplane, using the same 24V supply for field power and the controller is generally acceptable in a single-panel installation. If field devices are on a different electrical system, a separate isolated supply avoids ground loop currents that appear as output errors.

Q: What happens to the outputs when the controller faults or goes to program mode?

Output behavior on controller fault is configurable in Studio 5000 — options are hold last value or go to a defined output value. Set this according to the fail-safe requirement of the connected field device.

Q: Can both channels run in different modes simultaneously — one voltage, one current?

Yes. Each channel's output mode is configured independently. Channel 0 can be in 4–20 mA while channel 1 is in 0–10V, or any other combination the application requires.

Q: The accuracy is ±0.5% — is that sufficient for tight process control loops?

For most industrial process control applications, ±0.5% is adequate. It represents ±0.08 mA on a 4–20 mA range, or ±50 mV on a 0–10V range. Loop accuracy is typically limited by sensor and actuator uncertainties, not the analog output module. For metrology-grade applications, a higher-resolution isolated output module is more appropriate.

1769-OF2 New Original Compact I/O Output Module 1769OF2