Quick Answer
Before signing a calibration AMC, confirm the laboratory's accredited scope covers every instrument and range in your list, that calibration intervals are stated per instrument rather than applied uniformly, that turnaround time and onsite cover are defined with consequences, that out-of-tolerance handling is written in, and that your calibration records remain yours if the contract ends.
Key Takeaways
- An AMC that does not name the accredited scope per instrument is the single most common gap.
- A uniform annual interval across every instrument is a finding waiting to happen — intervals belong in the contract, per instrument.
- Turnaround time without a consequence clause is a target, not a commitment.
- Out-of-tolerance handling must be defined before it happens, not negotiated afterwards.
- Your calibration history is your compliance record — confirm you keep it if the contract ends.
Clause 1 — Accredited Scope, Instrument by Instrument
This is where most contracts quietly fail. A laboratory holds NABL accreditation for defined parameters and defined ranges, not for calibration in general. A contract that says the laboratory is NABL accredited tells you nothing about whether it is accredited for your 400 bar pressure gauge or your 0.01 mg analytical balance.
What to ask for
Attach your full instrument list to the contract as an annexure, with parameter and range for each. Ask the laboratory to mark which items fall inside its accredited scope and which do not. Items outside scope can still be calibrated, but you need to know which certificates will carry accredited status before an auditor tells you.
Accreditation scopes change at renewal. A clause requiring the laboratory to notify you of any scope change affecting your instrument list costs nothing to include and prevents a surprise.
Clause 2 — Intervals Stated Per Instrument
Most AMCs apply a single annual cycle to everything. That is administratively convenient and difficult to defend, because a uniform interval implies no assessment was made of individual instruments.
A defensible interval rests on the manufacturer's recommendation, the instrument's own drift history, the criticality of the measurement, and the conditions it works in. Some instruments justify six months; others justify two years. Put the agreed interval for each instrument in the annexure, and include a clause allowing it to be revised when drift history suggests it should be.
| Instrument situation | Interval direction | Why |
|---|---|---|
| No measurable drift across three cycles, controlled environment | Can be extended | Evidence supports a longer cycle |
| Drifted at two consecutive calibrations | Should be shortened | The current interval is not catching drift in time |
| Production floor, vibration, frequent handling | Shorter than catalogue default | Conditions of use are harsher than assumed |
| Directly supports batch release or safety | Shorter, regardless of drift | Consequence of failure is high |
Clause 3 — Turnaround Time With a Consequence
Almost every AMC states a turnaround time. Far fewer state what happens when it is missed. Without a consequence, the number is an aspiration.
- Define turnaround from collection to certificate delivery, not from when work begins
- Separate standard turnaround from an urgent option, with the urgent charge agreed in advance rather than quoted at the moment you need it
- State what happens on a miss — a credit, a free urgent slot, or an escalation contact
- Agree a maximum instrument-out-of-service window for anything that stops production
Clause 4 — Onsite Cover and What Counts as a Visit
Onsite calibration is where AMCs most often diverge from expectations. The ambiguity is usually in what triggers a chargeable visit.
How many visits are included
State the number of scheduled onsite visits per year, and whether unscheduled calls are included or chargeable.
What a visit covers
A fixed number of instruments, a fixed number of engineer hours, or an open scope. Open scope sounds generous until the engineer runs out of day.
Who supplies what onsite
Reference standards, power, isolation, and access are the usual gaps. Agree who arranges plant shutdown or line isolation if it is needed.
What happens if an instrument cannot be calibrated onsite
Some instruments will have to go to the laboratory. Define who transports, who insures in transit, and whether that counts against your visit allowance.
Clause 5 — Out-of-Tolerance Handling
When an instrument is found out of tolerance, two things must happen quickly: you are told, and the record is written in a form your auditor will accept. Both belong in the contract rather than in whatever the engineer decides on the day.
- The laboratory notifies you before adjusting the instrument, so you can decide whether as-found data is needed
- As-found and as-left readings both appear on the certificate — as-found is what your impact assessment depends on
- A defined notification route and timescale, not a message to whoever signed the gate pass
- Agreement on who bears the cost of re-calibration after adjustment
Why as-found data matters
If an instrument is adjusted before the as-found condition is recorded, you cannot determine how far it had drifted. Without that figure, a product impact assessment has no basis, and the assessment is what an inspector asks for.
Clause 6 — Records, Reminders and Exit
Your calibration history is part of your compliance record. If it lives only in the laboratory's system, changing supplier becomes expensive.
| What to agree | Why it matters |
|---|---|
| Certificates delivered in a durable format you retain | Audit evidence must survive the contract |
| Full calibration history exported on request | Interval justification depends on drift history across years |
| Due-date reminders with lead time | The commonest audit finding is an instrument used past its due date |
| Record retention period at the laboratory | A reissue request years later should be possible |
| Handover terms at exit | A new supplier needs the history to set intervals sensibly |
The Pre-Signature Checklist
- 1.Instrument annexure attached, with parameter and range for every item
- 2.Each item marked as inside or outside the laboratory's accredited scope
- 3.Agreed calibration interval stated per instrument, not applied uniformly
- 4.Turnaround time defined from collection to certificate, with a stated consequence for a miss
- 5.Number of onsite visits and what each visit covers
- 6.Out-of-tolerance notification route, timescale, and as-found data commitment
- 7.Certificate delivery format and record retention period
- 8.Calibration history export and handover terms at exit
- 9.Scope-change notification clause
Prism Calibration Centre operates under NABL accreditation CC-2480 from GIDC Vatva, Ahmedabad, with calibration covering more than 200 instrument types and onsite service across Gujarat's industrial zones. Scope documentation is provided with any contract discussion so that the annexure above can be completed before signature rather than after.
Frequently Asked Questions
What should a calibration AMC include?
An instrument annexure listing parameter and range for every item, each marked as inside or outside the laboratory's accredited scope; the agreed calibration interval per instrument; turnaround time measured from collection to certificate with a stated consequence for a miss; the number of onsite visits and what each covers; out-of-tolerance notification terms including as-found data; and record retention and handover terms at exit.
Why does accredited scope matter in a calibration contract?
NABL accreditation is granted for defined parameters and defined ranges, not for calibration in general. A laboratory accredited for pressure to 100 bar is not accredited for a 400 bar gauge, and the certificate will still carry the accreditation symbol. Marking each instrument as inside or outside scope before signature tells you which certificates carry accredited status, rather than discovering it during an audit.
Should every instrument have the same calibration interval?
No, and a uniform annual interval applied across every instrument is itself a common audit finding, because uniformity implies no assessment was made. Intervals should follow the manufacturer's recommendation, the instrument's drift history, the criticality of the measurement and the conditions of use. Some instruments justify six months, others two years. Put the agreed interval per instrument in the contract annexure.
What is as-found data and why should it be in the contract?
As-found is the instrument's condition when it arrives, before any adjustment. As-left is its condition after calibration. If an instrument is adjusted before as-found is recorded, you cannot determine how far it had drifted, and a product impact assessment then has no basis. A contract clause requiring as-found data and notification before adjustment protects that position.
Who owns the calibration records when a contract ends?
That depends entirely on what the contract says, which is why it should say something. Your calibration history is part of your compliance record and supports your interval justification across years. Agree that certificates are delivered in a durable format you retain, that full history is exported on request, and that handover terms apply at exit so a new supplier can set intervals from real drift history.
Written by
Er. Parthiv Kinariwala
Managing Director · Prism Calibration Centre · NABL CC-2480 · Ahmedabad
Er. Parthiv Kinariwala founded Prism Calibration Centre in 2004 and has over 20 years of hands-on experience in calibration engineering, NABL accreditation, and industrial compliance. His team performs 10,000+ calibrations annually from the Vatva GIDC laboratory, serving 5000+ industries across Gujarat.
Prism Calibration Centre — Vatva GIDC, Ahmedabad
Prism Calibration Centre
F-101, Rudraksh Complex 2, Phase 3, GIDC Vatva, Near Jasoda Nagar Cross Road, Ahmedabad — 382445, Gujarat, India
Phone: +91 98245 26444
Email: info@prismcalibration.com
NABL: CC-2480 · ISO/IEC 17025:2017
Hours: Mon–Sat, 9:00 AM – 7:00 PM