Test Rig Failure Detection & Pre-Fault Data Capture

Can a test rig capture what happened just before a failure? Learn how rolling data buffers can preserve critical pre-fault data and automatically capture the test condition when a protection event occurs, test rig failure detection

PROLABS Engineering Team

9/26/20262 min read

In an automated durability test, detecting a fault is only the first step. When a UUT goes out of specification or a protection limit is reached, the test rig may stop immediately—but the most useful information may be the data recorded just before the fault.

This is where pre-fault data capture becomes valuable.

The Challenge

A test system may need to detect conditions such as:

Overload
Over torque
Over current or voltage
Over temperature
Excessive displacement or speed
UUT failure or breakage
Out-of-spec conditions

Once the protection system stops the test, engineers need to understand what led to the fault.

Continuously saving the entire test may not always be practical. A better approach is to continuously retain only the most recent data.

The Rolling Buffer Method

A rolling data buffer continuously acquires and stores test data at a defined sampling rate.

As new data arrives, older data is removed.

Therefore, the buffer always contains a defined period of the latest test history.

For example:

Continuous Acquisition

→ New data enters buffer
→ Old data is discarded
→ Buffer continuously updates
→ Fault occurs
→ Buffer is frozen
→ Pre-fault data is saved

This allows the system to capture the events immediately preceding the fault.

What Happens When a Fault Occurs?

The test software can monitor protection and status signals continuously.

When a fault condition is detected:

Fault Detection → Test Stop → Buffer Freeze → Data Save → Screenshot Capture

The saved data can contain the critical signals immediately before the event, while the automatic screenshot records the visual state of the test application.

Why Pre-Fault Data Is Important

A final fault message may tell you what stopped the machine, but the preceding data can help determine why it happened.

Engineers can examine:

Which parameter changed first
Whether the value was gradually increasing
The actual condition immediately before failure
The relationship between different signals
Whether a protection limit was approached
How the UUT behaved before the event

This turns a simple test failure into useful engineering information.

Applications

Pre-fault data capture can be useful in:

Durability testing
Endurance testing
Performance testing
Automotive component testing
Machine protection
Automated validation systems
Condition monitoring

Beyond Conventional Data Logging

A conventional data logger records what happened.

A well-designed automated test system can go further—it can continuously prepare to capture the evidence of a failure before the failure occurs.

The combination of a rolling buffer, fault detection and automatic event capture provides a practical foundation for smarter test systems and machine health monitoring.

How PROLABS Approaches Test Automation

PROLABS develops automated test applications that can combine data acquisition, real-time monitoring, protection handling, fault-event capture and automated reporting.

These techniques can be integrated into new test rigs as well as existing machines being upgraded with modern test automation software.