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Concept

Concept


Products: AO-8, AO-V-8, DI-16, DO-FA-12, DO-FC-8, RTD-DI-16, UI-16, UI-8/AO-4, UI-8/AO-V-4, UI-8/DO-FC-4
Functionalities: Hardware
Product version: 3.3, 2022, 2023, 2024, 7.0
3/31/2022

Override Switches and Potentiometers

arrow1_rotationOverride Switches arrow1_rotationPotentiometers

For Central IO modules with outputs, the following components on the front provide control of the output channels:

  • Override switches

  • Potentiometers

The Hand-Off-Auto (HOA) override switches on Central IO modules with manufacturing date earlier than 2021-W26 must be disabled to remove the risk of an improper output. To disable the override switches, update the Central IO module firmware to version 2.017 or later. For more information, see Important Information on Central IO Modules with Manufacturing Date Earlier Than 2021-W26 .

Notice

EQUIPMENT DAMAGE

For Central IO modules with Hand-Off-Auto (HOA) override switches and with manufacturing date earlier than 2021-W26:

  • Disable the HOA switches by updating the Central IO module firmware to version 2.017 or later.

Failure to follow these instructions can result in equipment damage.

 
action_zoom_plus_stroke Override switches and potentiometers
Figure: Override switches and potentiometers

Override Switches

Central IO modules with analog or digital outputs are available with Hand-Off-Auto (HOA) override switches on the front of the Central IO module. The switches provide override control of the output channels. The analog and digital output channels operate differently depending on the type of output:

  • Analog outputs work in conjunction with the potentiometers to manually adjust the voltage or current output by the channel.

  • Digital outputs are used with Form A or Form C relays to open and close relay contacts.

 
action_zoom_plus_stroke Form A and Form C relays
Figure: Form A and Form C relays

The output of the channel can be directed from program control or manual control. The output can be disabled as well.

The following table describes the actions associated with each position of the analog override switch.

Table: Analog Override Switch

Switch Position

Action

HAND

Using the potentiometer, you can manually adjust the voltage or current of the output. Programs have no effect on the output when the switch is in this position.

AUTO

Programs control the output.

OFF

The voltage or current is set to zero scale. Programs have no effect on the output when the switch is in this position.

The following table describes the actions associated with each position of the digital override switch.

Table: Digital Override Switch

Switch Position

Action

HAND

The output relay is energized to an ON state. Programs have no effect on the output when the switch is in this position.

AUTO

Programs control the output.

OFF

The output relay is de-energized to an OFF state. Programs have no effect on the output when the switch is in this position.

Potentiometers

Each analog output channel contains a potentiometer that allows you to manually adjust the voltage or current output by the channel. These potentiometers are one-turn with a range of values from zero to full-scale.

 
action_zoom_plus_stroke Potentiometers
Figure: Potentiometers

The potentiometers are used in conjunction with the override switches to manually adjust the current or voltage output of the analog output channel.

See Also

  • Hardware Overview
  • Central IO Modules
  • Important Information on Central IO Modules with Manufacturing Date Earlier Than 2021-W26