Tester Verification Before Production Deployment

Why Verification?

Using an unverified tester can lead to false quality judgments, increased costs due to defects, or even a loss of customer trust. Verification ensures that the tester's measurement system is accurate, stable, and capable of performing the intended measurements as required by the customer.

Key Methods of Tester Verification

1. MSA – Measurement System Analysis

MSA (Measurement System Analysis) is a methodology that assesses the quality of the measurement system itself before analyzing products. In practice, it verifies the extent to which the measurement process is affected by errors—whether due to the device, the operator, or other influences.

• Evaluates repeatability and reproducibility.
• Estimates measurement variability vs. product variability.
• Helps determine if the measurement system provides trustworthy data.

Recommended: when introducing a new tester, after hardware/software changes, or when suspecting measurement errors.

2. Gage R&R – Gauge Repeatability and Reproducibility

The Gage R&R method is a core part of MSA and quantifies the measurement error caused by the instrument and operator.

• Tests measurement repeatability and reproducibility across multiple operators and parts.
• Outputs %GRR – the percentage of total variation explained by the measurement system.
• Values below 10% indicate a capable system; above 30% require improvement.

???? Software like Unilab or statistical packages in corporate test systems automate this calculation.

3. Cp and Cpk – Process Capability

Cp (Process Capability Index) and Cpk (Process Capability Index adjusted for centering) assess how well measurement outputs fit within specified tolerances.

• Cp evaluates spread against the tolerance band (regardless of centering).
• Cpk also considers whether the process is centered.
• Values above 1.33 are considered standard for capable processes.

Cp/Cpk is especially useful in stable, repeatable serial production testing.

Other Important Tester Verification Steps

4. Calibration Check

Each tester must undergo verified calibration, ideally against traceable standards (e.g. per ISO/IEC 17025). Calibration verifies the accuracy of analog/digital inputs, measurement channels, and application software.

????️ Calibration should be done before production deployment and periodically as per the calibration plan.

5. Software and Firmware Review

Test software and firmware must be validated:

• Functional tests (unit tests, scenario checks) per customer specifications.
• Verification of input limits and error responses, as defined by the customer.
• Validation of outputs and exported data.

Verification is documented and archived to demonstrate compliance with quality standards (e.g. ISO 9001, IATF 16949).

6. Testing with Golden Sample / Reference Unit

Using a golden sample—a unit with well-known characteristics—helps confirm that the tester evaluates known states correctly. This method is highly effective when combined with MSA and Cp/Cpk. It may involve multiple golden samples representing product variants or specific error states (e.g. deviation levels, connection faults, or limit-tolerance states).

Golden sample testing is applied in:

• Tester startup (self-check)
• Fixture or adapter changes
• Regular checks – per internal verification plan

Testing frequency depends on process criticality. Typical intervals:

• Once per shift (multi-shift operations)
• Daily (low-usage systems)
• Weekly or ad hoc (non-critical, stable processes)
• Immediately after maintenance or software update

 These intervals are usually part of internal work instructions or a control plan. Deviating from them may compromise test result validity.

CMT Tester by Unites Can:

• Distinguish between golden samples by batch, product type, or defined state
• Automatically assign the correct golden sample based on test program, serial number, or input metadata
• Enable operators to validate not just "pass/fail" but also the accuracy of specific fault diagnostics

This level of flexibility is essential in environments with high product variability (e.g. customer variants or NPI – New Product Introduction).

 For the customer, this means greater confidence in the tester's results and the ability to track quality accurately even in complex manufacturing setups.

Summary: What Makes Quality Tester Verification?

Conclusion

Tester verification is not a one-time formality—it is a systematic process aimed at ensuring the trustworthiness of every measurement a tester performs. By combining methods such as MSA, Gage R&R, Cp/Cpk with calibration and controlled software, you can be confident that tester outputs reflect reality.

At Unites, we apply these principles not only in new device development but also during customer deployment—ensuring every test system delivers reliable, trustworthy data.