NABL Calibration Service Selection
How to Verify NABL Calibration Scope Before Ordering or Accepting a Certificate
A laboratory can be NABL accredited without every calibration service it offers being covered by the same accredited scope. The practical check is not the logo alone. Compare your measurement requirement with the laboratory's current scope, including discipline, measurand or instrument, method, range, CMC and service location where applicable.
Why NABL Scope Verification Matters
NABL's FAQ defines scope of accreditation as the specific tests or calibrations for which a laboratory has been found competent. For calibration laboratories, the scope can include the discipline or group, measurand or instrument, calibration method, measurement range and Calibration and Measurement Capability, commonly abbreviated CMC.
This is why "NABL accredited" is not enough information for procurement. The question is whether the exact calibration you need is inside the current accredited scope.
Your existing calibration service selection guide helps compare laboratories broadly. This page has a narrower job: verifying accredited scope for one specific requirement.
1. Define the Measurement Requirement Before Searching
| Requirement | Example of what to define |
|---|---|
| Instrument or measurand | Pressure gauge, micrometer, torque wrench, mass standard, temperature indicator |
| Range | The actual range used in your process, not only the instrument's maximum range |
| Calibration points | Points important to normal or critical use |
| Required uncertainty | The level needed to support your measurement decision |
| Method or configuration | Any method, sensor, channel, accessory or setup that matters |
| Location | Permanent laboratory, customer site or another permitted facility |
| Certificate needs | As-found data, as-left data, conformity statement or other agreed evidence |
If these requirements are unclear, use the guide to what customers should specify before ordering calibration.
2. Find the Laboratory and Open Its Current Scope
NABL's current FAQ directs users to the laboratory search, where they can select the calibration field, discipline and group, open the laboratory details and view the scope of accreditation. NABL states that the detailed scope can be downloaded from the certificate number and reviewed for parameters, range and CMC.
Record the laboratory name, certificate number, scope version or date where available, and the date you performed the check. This creates evidence that the procurement decision was based on the scope available at that time.
3. Check the Discipline, Group and Instrument or Measurand
Start with the exact item you need calibrated. Similar sounding services can belong to different disciplines or groups. Do not assume that accreditation for one instrument family automatically includes another.
For a multifunction device, check whether the scope covers every parameter you intend to order. A laboratory may be competent for one function and not another.
4. Check the Calibration Method and Measurement Range
NABL 100B describes calibration scope entries using items such as discipline or group, measurand or instrument, calibration or measurement method, measurement range and CMC. Compare those entries with your intended use.
A scope that reaches the instrument's maximum nominal range is not automatically sufficient if the relevant method, parameter or service location differs from your requirement. Conversely, a scope can be suitable even when your instrument has a wider nameplate range, provided the part of the range you actually need is covered and the service meets your requirement.
5. Understand CMC Before Comparing Laboratories
CMC describes an accredited calibration and measurement capability under specified conditions. It is a capability statement in the scope. It should not be treated as automatically identical to the expanded uncertainty on every customer certificate.
Use CMC as one input when deciding whether the laboratory can support the uncertainty you need. The reported uncertainty for the actual calibration can be different because it depends on the specific instrument, method, conditions and result.
For certificate interpretation, see measurement uncertainty on a calibration certificate.
6. Check Whether the Required Calibration Location Is Covered
NABL documentation distinguishes permanent laboratory activities and, where applicable, site or mobile activities. If you need on-site calibration, verify that the scope identifies the relevant site capability rather than assuming a permanent-facility accreditation automatically covers work at your plant.
Site work can involve additional practical controls, such as transport of standards, environmental conditions and checks before or after field use. Your purchase order should make the required location explicit.
7. Compare the Issued Certificate With the Scope You Verified
Scope verification should be repeated when the certificate is accepted, especially for important measurements. Compare:
- Laboratory identity and accreditation number.
- Instrument or measurand.
- Calibrated range and points.
- Method where relevant.
- Calibration location.
- Reported uncertainty.
- Any statement that distinguishes accredited and non-accredited work.
Then use the calibration certificate guide to review results, uncertainty, traceability, as-found/as-left data and conformity.
Purchase-Order Questions to Ask Before Sending the Instrument
- Is this exact instrument or measurand included in your current NABL scope?
- Does the accredited range cover the points we need?
- What CMC is listed for the relevant range and method?
- Can you provide the uncertainty needed for our intended use?
- Is the work covered at the required location?
- Will as-found data be recorded before any adjustment?
- Will a conformity statement be provided, and what decision rule will apply?
- Will any requested work fall outside the accredited scope?
These questions also complement the guide to comparing NABL calibration quotations beyond price.
Record the Scope-Verification Decision
| Decision | Meaning | Typical next action |
|---|---|---|
| Suitable | Scope aligns with the defined requirement | Proceed with ordering and preserve verification evidence. |
| Suitable with limitation | Only part of the needed range, function or location is covered | Restrict the order or seek additional capability. |
| Clarification required | Scope wording or capability is not clear enough | Ask the laboratory for clarification before ordering. |
| Not suitable | Required calibration is outside the verified scope | Select another accredited capability or document a justified alternative. |
Do not turn this into a simple logo check. The purpose is to connect the laboratory's accredited capability with the measurement decision your organization must support.
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