Control of Measuring Equipment in Manufacturing Plants: What Should FDI Enterprises Consider Under ISO 9001?

A calibration label or certificate alone does not demonstrate that measuring equipment is suitable for the measurement being performed. The plant also needs to review calibration results, define conditions of use and assess the potential impact on products if the equipment deviates from specified requirements.

For FDI enterprises, measuring equipment control also needs to align with the technical requirements of the corporate group and customers. This article explains which equipment should be controlled, when verification, calibration or metrological verification may be required, and how records and deviations should be managed under ISO 9001.

Table of contents

What Does ISO 9001 Require for Monitoring and Measuring Resources?

When monitoring or measurement results are used to verify the conformity of products and services, the organisation needs to ensure that the results are valid and reliable. Clause 7.1.5 of ISO 9001:2015 can be summarised into five key requirements:

Provide suitable resources: Determine and provide the resources required for the monitoring and measurement activities to be performed.
Maintain fitness for purpose: Maintain resources so that they remain fit for their intended purpose and retain documented information as evidence.
Ensure measurement traceability where required: When traceability is a requirement or is considered essential for confidence in measurement results, measuring equipment needs to be calibrated, verified, or both, at specified intervals or prior to use. Measurement standards should be traceable to national or international measurement standards. Where such standards are unavailable, the basis used for calibration or verification should be retained.
Identify status and protect equipment: Clearly identify equipment status and protect equipment from adjustments, damage or deterioration that could affect calibration status and subsequent measurement results.
Assess the impact on previous measurement results: When equipment is found unsuitable for its intended purpose, determine the validity of previous measurement results and take appropriate action regarding the affected results and related decisions.

Which Equipment in a Manufacturing Plant Needs to Be Controlled?

1. Determine Control Requirements Based on the Purpose of Measurement

The scope of control should start with one question: What decision is made based on the measurement result? Equipment should be considered for control when its results are used to accept incoming materials, monitor parameters affecting quality or accept finished products. The level of control depends on the measurement requirements and the potential consequences of inaccurate results.

2. Review Equipment at Each Process Stage

Enterprises should review equipment according to the actual production sequence. This approach helps identify devices located on production lines or integrated into machinery.

Process stage	Examples of equipment to review	Role of measurement results
Incoming material inspection	Scales, calipers, micrometers	Verify incoming acceptance criteria
Processing and production	Temperature sensors, pressure gauges	Monitor parameters affecting quality
Finished product inspection	Dimensional measuring equipment, scales	Support product acceptance decisions
Product storage	Temperature and humidity monitoring devices	Control specified storage conditions

3. Distinguish Between Equipment Used to Verify Conformity and Reference-Only Equipment

A caliper used to inspect dimensions against an engineering drawing requires appropriate control because its measurement results support product acceptance decisions.

By comparison, a ruler used only for preliminary estimation during workpiece preparation may be managed as reference-only equipment, provided its results are used solely for estimation rather than product acceptance, machining parameter decisions or control of parameters affecting quality.

Enterprises should also ensure that a “reference only” label reflects the equipment’s actual use. Equipment used to determine product conformity requires the corresponding level of control.

4. Review Customer, Corporate and Applicable Regulatory Requirements

FDI manufacturing plants should compare their equipment list against engineering drawings, control plans, customer requirements and corporate technical specifications. In parallel, applicable metrology regulations should be reviewed to determine which measuring instruments are subject to mandatory controls based on equipment type and intended use.

Hypothetical example: A plant receives equipment from its corporate group together with an overseas calibration certificate. Before putting the equipment into service, the responsible person should verify the equipment identification, calibration range and the plant’s measurement requirements. This review determines whether the existing documentation adequately demonstrates suitability or whether additional control activities are required.

What Is the Difference Between Calibration, Metrological Verification and Verification?

1. Understand the Purpose of Each Activity

These three activities serve different purposes. Depending on the applicable legal and technical requirements, one item of equipment may require a combination of control activities.

Activity	Purpose	Key consideration for enterprises
Calibration	Establishes the relationship between values provided by measurement standards and corresponding indications from the equipment, taking measurement uncertainty into account. This information supports the determination of measurement results.	Calibration and equipment adjustment are separate activities. Enterprises should evaluate calibration results against the requirements of the intended measurement.
Metrological verification	Evaluates and confirms that the metrological characteristics of a measuring instrument meet applicable metrological technical requirements.	Where mandatory requirements apply, enterprises should comply with requirements concerning the relevant instruments, verification regime and authorised implementation arrangements.
Verification	Provides objective evidence that equipment fulfils specified requirements.	Defined acceptance criteria, appropriate methods and suitable evidence should be established. This activity serves a different function from mandatory metrological verification.

Definitions of calibration and verification can also be referenced in the International Vocabulary of Metrology (VIM).

Regulatory note:

Circular 45/2026/TT-BKHCN, effective from 1 September 2026, amends several regulations to simplify administrative procedures in the field of metrology. Chapter II amends Circular 23/2013/TT-BKHCN concerning Group 2 measuring instruments, while Chapter III amends Circular 54/2025/TT-BKHCN concerning verification, calibration and testing activities.

Mandatory metrological verification obligations should therefore be determined according to the type of measuring instrument, its intended use and the applicable regulations, including relevant amendments and supplements.

2. Define Appropriate Control Intervals

ISO 9001:2015 does not prescribe a universal 12-month interval for all measuring equipment. Enterprises should determine intervals according to the relevant control requirements:

Mandatory metrological verification: Follow the applicable statutory intervals and circumstances requiring verification.
Calibration or verification: Establish intervals based on applicable requirements, manufacturer recommendations, frequency of use, operating environment, deviation history and potential impact on quality.
Interval review: Reassess the interval when equipment stability deteriorates or when operating conditions or applicable requirements change. ILAC-G24:2022/OIML D 10:2022 may be used as a reference.

3. Evaluate Calibration Results Before Use

After receiving a calibration certificate, competent personnel should review five areas before approving the equipment for use:

Equipment information:Match the equipment identification and serial number, where applicable, on the certificate with the actual equipment.
Calibration scope: Confirm that the measurement range, calibration points and relevant conditions cover the intended measurements at the plant.
Acceptance criteria: Compare the evaluation criteria, including any criteria used to state conformity on the certificate, with the intended use requirements.
Result data: Review measurement error (the difference from the reference value), correction (the value used to compensate for systematic measurement error) and measurement uncertainty (the dispersion associated with the measured value) to evaluate suitability.
Decision for use: Record the evaluator, the decision on equipment use and any applicable scope or conditions of use.

Process for Controlling Measuring Equipment in a Manufacturing Plant

Enterprises can manage measuring equipment through the following six-step process:

Step	Key actions and outputs
1. Identify equipment requiring control	Review measurements, intended use and applicable requirements to define the scope of control.
2. Identify and register equipment	Assign equipment IDs, establish an equipment register and define management responsibilities.
3. Determine control methods and intervals	Plan metrological verification, calibration or verification activities; define intervals and acceptance c
4. Implement the control plan	Assign competent personnel or qualified service providers, meet applicable conditions and retain the results.
5. Evaluate results and update equipment status	Record the decision for use and clearly identify equipment status, scope and limitations of use.
6. Maintain records and monitor equipment	Retain equipment history, track upcoming due dates, ensure appropriate storage and record incidents, repairs or adjustments.

Depending on risk and applicable requirements, the equipment ID should be linked to product inspection records. This traceability helps identify potentially affected batches when a measurement deviation occurs.

How to Handle Overdue or Non-Conforming Measuring Equipment

Before taking action, enterprises should distinguish between three situations:

Situation	Key consideration
Overdue for metrological verification, calibration or verification	The required control activity has passed its due date. The equipment’s actual measurement condition still requires evaluation.
Failure to meet acceptance criteria	Evidence shows that the equipment does not meet the measurement requirements for its intended use.
Impact, damage or abnormal adjustment	There is a basis to question measurement capability even when the scheduled control period remains valid.

Step 1. Prevent Further Use of the Equipment

Temporarily suspend the equipment from measurements that may be affected. Identify its status clearly and prevent unintended use. Carry out the appropriate metrological verification, calibration, verification or repair. Return the equipment to service after confirming that it meets the required conditions.

Step 2. Define the Potentially Affected Measurement Results

Use the equipment history, most recent control results, control due date and timing of the incident to define the period and measurements requiring review. Inspection or calibration results obtained before repair or adjustment can provide useful evidence for evaluating the extent of deviation. Therefore, the assessment should cover the relevant period rather than focusing solely on the date when the issue was detected.

Step 3. Evaluate and Manage Related Products

Identify the relevant products or batches and determine whether remeasurement, segregation or other actions are appropriate based on available evidence and applicable requirements.

When equipment fails to meet requirements, the affected products should be evaluated according to the magnitude of the deviation, product requirements and the feasibility of reinspection.

Where delivered products are affected, follow the applicable notification and response requirements, customer agreements and corporate procedures. Retain records of the assessment and actions taken.

Common Measuring Equipment Control Issues in FDI Enterprises

Applying the same control regime to all equipment despite differences in intended use and potential impact.
Applying a default 12-month interval to every device without considering usage history or specific customer and corporate requirements.
Checking only the calibration due date while overlooking whether calibration results are suitable for the actual measurement.
Failing to clearly identify reference-only equipment, creating a risk of unintended use.
Lacking sufficient record linkage to identify products potentially affected by equipment deviation.
Applying inconsistent requirements across the plant, corporate group and customer, resulting in unsuitable control intervals, calibration scopes or acceptance criteria.

Checklist for Preparing for a Customer Audit

Area that may be reviewed	Evidence to prepare
Does the equipment register include all equipment requiring control?	Equipment register cross-checked against actual equipment and control plans.
Are control methods and intervals appropriate?	Control plan, basis for determining intervals and applicable requirements.
Have calibration results been evaluated?	Evaluation records against acceptance criteria and documented decisions for use.
Are the personnel or service providers competent?	Competence records, measurement standards and accreditation or designation scope where required.
Are equipment status and limitations of use clearly defined?	Labels, equipment management information and operating instructions.
Is equipment properly stored and monitored?	Storage instructions, monitoring schedules and repair records, where applicable.
Can affected products be identified?	Records linking equipment to inspection results and records of actions taken where issues have occurred.

Frequently Asked Questions (FAQ)

Question	Answer
Does every measuring device need to be calibrated?	The appropriate control method depends on the intended use, the impact of the measurement result and applicable requirements. Depending on these factors, equipment may require metrological verification, calibration, verification or another suitable control method.
Is external calibration mandatory?	ISO 9001:2015 allows organisations to establish suitable arrangements for calibration activities. Where calibration is performed internally, the organisation should ensure appropriate competence, methods, measurement standards and records, while meeting all applicable requirements.
Does customer-owned measuring equipment need to be controlled?	Yes, when its measurement results are used to determine conformity or control parameters affecting quality. The plant should agree responsibilities with the customer and confirm that the equipment is suitable before use.
Can equipment still within its control interval continue to be used after an impact?	Its condition should first be evaluated, with use suspended for measurements that may be affected. The equipment can return to service once its suitability has been confirmed.
Does every measuring instrument in the plant require mandatory metrological verification?	Mandatory metrological verification requirements depend on the type of measuring instrument, intended use and applicable legislation. Equipment outside the mandatory verification scope still requires appropriate controls when its results are used to verify specified requirements.

ISO 9001 Assessment and Certification with ARES Vietnam

Effective control of measuring equipment helps maintain the reliability of measurement results and quality-related decisions within the management system.

Is your organisation preparing for an initial certification, surveillance or recertification audit? Contact ARES Vietnam to discuss ISO 9001 assessment and certification needs appropriate to your scope of operations.