How to PAT Test a Computer Monitor: A Complete Step-by-Step Guide

Computer monitors are among the most common pieces of electrical equipment in modern workplaces, yet many people are unsure about the proper PAT testing procedures for these devices. Whether you’re a business owner ensuring compliance or a PAT testing professional looking to refine your technique, this comprehensive guide will walk you through everything you need to know about safely and effectively PAT testing computer monitors.

Understanding Computer Monitors in PAT Testing Context

Computer monitors fall into the category of portable electrical appliances that require regular PAT testing. Despite being relatively stationary in most office environments, they’re considered portable because they can be easily moved and plugged into different sockets. This classification means they must be included in your PAT testing schedule.

Types of Computer Monitors

LCD/LED Monitors:

• Most common type in modern offices
• Lower power consumption
• Typically Class I equipment (earthed)
• Standard testing procedures apply

CRT Monitors (older models):

• Higher power consumption
• Heavier construction
• May require additional safety considerations
• Less common but still found in some workplaces

Gaming/Professional Monitors:

• Higher power requirements
• May include additional features (USB hubs, speakers)
• Require comprehensive testing of all functions

Pre-Testing Preparation

Safety First

Before beginning any PAT testing procedure:

1. Ensure the monitor is switched off and unplugged from the mains
2. Allow cooling time if the monitor has been in use
3. Clear the work area of any obstructions
4. Check your testing equipment is calibrated and functioning
5. Wear appropriate PPE if required by your procedures

Initial Assessment

Document the monitor:

• Make and model number
• Serial number
• Asset tag or identification number
• Location and user information
• Previous test results (if available)

Visual inspection checklist:

• Power cable condition
• Plug integrity
• Monitor casing for cracks or damage
• Ventilation grilles clear of dust
• Any signs of overheating or burning

Step-by-Step PAT Testing Procedure

Step 1: Visual Inspection

Power cable examination:

• Check the entire length for cuts, kinks, or damage
• Inspect the plug for cracks or loose pins
• Ensure the cable isn’t trapped or stressed
• Look for any signs of overheating (discolouration, melting)

Monitor casing inspection:

• Check for cracks or damage to the plastic casing
• Ensure ventilation slots aren’t blocked
• Look for any loose screws or panels
• Check the screen for cracks (safety hazard)

Connection points:

• Inspect the power socket on the monitor
• Check any external power adapters
• Examine data cable connections (though these aren’t part of PAT testing)

Step 2: Earth Continuity Test

Why it’s crucial: Computer monitors are typically Class I appliances, meaning they rely on the earth connection for safety. This test ensures the earth path is intact.

Testing procedure:

1. Connect your PAT tester’s earth probe to an accessible earth point on the monitor
2. Connect the other probe to the earth pin of the plug
3. Apply the test voltage (typically 200mA for 5-10 seconds)
4. Record the resistance reading

Pass criteria:

• Resistance should be less than 0.1 ohms for portable appliances
• No open circuit indication
• Stable reading throughout the test

Common earth points on monitors:

• Exposed metal screws on the casing
• Metal connector housings
• Any accessible earthed metal parts

Step 3: Insulation Resistance Test

Purpose: This test checks that the insulation between live parts and earth is adequate to prevent dangerous leakage currents.

Testing procedure:

1. Ensure the monitor is switched off but plugged into your PAT tester
2. Set your tester to insulation resistance mode
3. Apply the test voltage (typically 500V DC for IT equipment)
4. Maintain the test for the required duration (usually 5 seconds)
5. Record the resistance reading

Pass criteria:

• Minimum 1 megohm (1MΩ) for most monitors
• Some sensitive equipment may require different criteria
• Check manufacturer specifications if available

Important considerations:

• Modern monitors with standby circuits may show lower readings
• Some monitors have surge protection that affects readings
• Always follow manufacturer guidelines where available

Step 4: Polarity Test

What it checks: Ensures that the live and neutral connections are correct and that any switches interrupt the live conductor.

Testing procedure:

1. Plug the monitor into your PAT tester
2. Select polarity test mode
3. The tester will check the wiring configuration
4. Record the results

Pass criteria:

• Live and neutral correctly connected
• Earth connection present and correct
• No reversed polarity indication

Step 5: Load Test (Functional Test)

Purpose: Tests the monitor under normal operating conditions to identify faults that might not show up in other tests.

Testing procedure:

1. Connect the monitor to your PAT tester’s load test facility
2. Switch on the monitor
3. Allow it to reach normal operating temperature
4. Measure the current consumption
5. Check for any unusual behaviour

What to monitor:

• Current draw within normal parameters
• No unusual noises or smells
• Screen displays correctly
• No flickering or distortion
• Ventilation fans operating correctly (if present)

Typical current consumption:

• Small LCD monitors (19-22″): 0.5-1.5 amps
• Large LCD monitors (24-27″): 1.0-2.5 amps
• Gaming/professional monitors: 2.0-4.0 amps
• Older CRT monitors: 3.0-6.0 amps

Special Considerations for Computer Monitors

Monitors with Built-in USB Hubs

Additional testing requirements:

• Test the monitor’s main power supply as normal
• Check that USB ports don’t affect electrical safety
• Ensure proper earthing of all metal USB connectors
• Verify that USB power doesn’t create overload conditions

Monitors with Integrated Speakers

Testing considerations:

• Audio circuits are part of the overall appliance
• May affect load test readings
• Check speaker grilles for damage
• Ensure audio doesn’t interfere with safety systems

External Power Adapters

When monitors use external power supplies:

• Test the power adapter as a separate appliance
• Check the low-voltage connection to the monitor
• Verify the adapter is the correct type for the monitor
• Ensure proper earthing arrangements

Common Issues and Troubleshooting

Failed Earth Continuity

Possible causes:

• Damaged earth wire in the cable
• Poor connection at the plug
• Faulty earth connection inside the monitor
• Corroded or loose earth points

Actions:

• Check and tighten plug connections
• Test with a known good cable
• If internal fault suspected, refer for repair

Poor Insulation Resistance

Possible causes:

• Moisture ingress
• Degraded internal insulation
• Surge protection circuits
• Standby power circuits

Actions:

• Allow drying time if moisture suspected
• Check manufacturer specifications
• Consider environmental factors
• Refer for specialist assessment if needed

High Current Consumption

Possible causes:

• Faulty internal components
• Incorrect voltage settings
• Aging components
• Overloaded circuits

Actions:

• Compare with manufacturer specifications
• Check voltage settings if adjustable
• Consider replacement if significantly over specification

Documentation and Labelling

Test Records

Essential information to record:

• Test date and technician details
• All test results with pass/fail status
• Any defects found and actions taken
• Next test due date
• Equipment identification details

Labelling Requirements

Pass labels should include:

• Test date
• Next test due date
• Unique appliance identifier
• Tester identification

Fail labels must indicate:

• Equipment failed testing
• Must not be used
• Date of test
• Reason for failure (if space permits)

Frequency of Testing

Standard Guidelines

Office environments:

• Annual testing for most monitors
• More frequent testing in harsh environments
• Consider usage patterns and environment

High-risk environments:

• 6-month intervals may be appropriate
• Dusty or humid conditions require more frequent testing
• Heavy usage may necessitate shorter intervals

Visual inspections: For equipment on 1-2 year testing cycles, visual inspections between full PAT tests are essential for maintaining electrical safety standards.

Industry-Specific Considerations

Office Environments

Common challenges:

• Large numbers of similar monitors
• Desk-based testing requirements
• Minimal disruption to work activities
• Cable management in confined spaces

Hospitality Settings

Special requirements:

• Guest room monitors require careful handling
• Conference room equipment needs flexible testing schedules
• Public area monitors may need more frequent inspection

Scheduling considerations: Many PAT testing companies offer flexible scheduling, including early morning and late evening appointments for hospitality businesses to minimise operational disruption.

Industrial Environments

Additional factors:

• Harsh environmental conditions
• Specialised monitoring equipment
• Safety-critical applications
• More frequent testing requirements

Best Practices for Efficient Testing

Preparation Tips

Before starting:

• Plan your route through the building
• Ensure adequate lighting for inspections
• Have spare labels and documentation ready
• Coordinate with building users

Testing Efficiency

Streamline your process:

• Group similar equipment together
• Use consistent testing sequences
• Maintain organized records
• Plan for equipment that fails testing

Quality Assurance

Ensure accuracy:

• Regular calibration of test equipment
• Consistent application of test procedures
• Proper documentation of all results
• Follow-up on failed equipment