Performing a Successful I/O Checkout

What is an I/O Checkout?

The I/O (input/output) checkout is an essential step in industrial automation system acceptance testing. It involves verifying the operation of all control and automation system input and output signals, ensuring the reliability of the install.

Typically an I/O checkout is conducted by an experienced automation controls engineer or technician.

Before an I/O checkout is conducted, there are a few essential documents that are required to be successful.

Required Documents for an I/O Checkout

There are at least 4 documents that are required for a succesful I/O checkout. They are:

• I/O List
• Schematic Wiring Diagram
• P&ID
• Network & System Configuration

The I/O List

An I/O List is the most important document for I/O checkouts. It serves as a comprehensive table that specifies all the input and output points of the control system, providing a structured overview of the system’s I/O requirements.

An I/O list contains detailed information about the various input and output devices connected to the PLC. This includes digital and analog inputs and outputs, sensors, actuators, and other devices involved in the automation system.

The list typically includes parameters such as device tags, device descriptions, signal types, scaling information, and any other relevant I/O configuration details.

With the help of an I/O list, the automation engineer and/or technicians can easily ensure proper wiring and device integration.

The I/O list acts as a reference and communication tool between the automation control specialist and other stakeholders involved in the design, installation, commissioning, and maintenance of the industrial control system.

Schematic Wiring Diagram

The Schematic Wiring Diagram (SWD), or simply “schematic”, is a graphical representation of the electrical wiring of a control panel.

In an I/O checkout procedure, a schematic wiring diagram plays a crucial role in ensuring the proper functioning and integration of the control system.

At this point in the commissioning process a point-to-point wiring check has ideally been completed. The SWD serves as a visual verification of signal paths and a troubleshooting aid.

Not only that, the automation engineer can use it to keep track of their progress in carrying out the I/O checkout procedure. Markups can be made by the automation engineer and later sent to drafters for editing.

P&ID

The P&ID (Process and Instrumentation Diagram) is a detailed schematic representation of the process flow, equipment, and instrumentation in an industrial controls system.

It provides a graphical illustration of the interconnectedness of various components and their relationships within the system.

During an I/O checkout you may need to find the physical location of process equipment and instrumentation in the field. The P&ID provides information that can help the automation engineer locate this equipment.

Often times the I/O list is built from the information on the P&ID. All components involved in the automation system are included on the P&ID, so it is an invaluable resource for linking process instrumentation in the field to entries on the I/O list.

Network & System Configuration

Communication systems are a key component of modern automation systems. Devices that rely on Ethernet, serial, Modbus, or other communication methods need to be configured properly.

A document specifying the network configuration of communication devices is a requirement for a succesful I/O checkout. Most of the time this information is included with the I/O list.

Have A Plan of Attack

Documentation is paramount to an I/O checkout, but in order for it to be successful you will need a plan.

This plan will differ based on the automation system you’re performing the checkout on. In general, the following points are worth considering:

• Tools and equipment preparation.
• Conduct a safety assessment and assess required PPE (Personal Protective Equipment).
• Draft a Power-Up and Power-Down Procedure if the checkout is expected to last more than one day.
• Consider prioritizing certain I/O points over other, less critical ones.
• Organize any logistics with facility personel.
• Have a methodical markup and documentation procedure.