Questions to ask before sending equipment for calibration

• Which points? For a 2–8 °C logger: perhaps 0, 5, 10 °C; for a −20 °C freezer logger: −25, −20, −15 °C.
• Which tolerance and decision rule for pass/fail? Or no conformity statement — just values and uncertainty.
• As-found and as-left both reported? Notify before adjusting?
• Calibrate the logger as a system (sensor plus electronics plus software readout) or the sensor only?
• Immersion depth and medium: liquid or dry block; in air for surface-mount loggers?
• Certificate format: electronic with unique ID; data in a machine-readable form if you manage many instruments.
• Turnaround and whether they hold instruments for an interval you cannot afford.
• Packaging, insurance and the handling of batteries in transit.

Under ISO/IEC 17025 clause 7.1 the laboratory must review your request and confirm it can meet it; a clear request makes that review meaningful.

Settle it in the purchase order

Under clause 7.1 the laboratory has to review your request and confirm it can meet it. That review is only meaningful if the request says something, and an order that reads calibrate this logger hands every decision below to whoever processes it.

The two lines that do the most work

Do not adjust without contacting us, and report as-found whether or not you adjust. Together they preserve the only evidence of how the instrument behaved during the interval that just ended — which is what you will need if a decision made three months ago is ever questioned, and what a routine adjust-and-report-as-left service quietly destroys.

The third contender is asking for results only with no conformity statement. It sounds like giving something up; it is usually the opposite. The laboratory does not know your application, and a pass under their default rule may not be a pass under yours. Numbers plus uncertainty let you make the judgement against the tolerance that actually applies.

Practical matters that ruin otherwise good jobs

• Packaging and transport. A reference PRT damaged in transit is common and expensive; agree who packs it, in what, and who carries the risk.
• Accessories. Send the readout if the instrument is calibrated as a system, and say so — a probe calibrated alone does not describe the pair.
• Configuration. State the measurement current, the wiring (three or four wire) and any coefficients loaded, so the calibration matches the way the instrument is used.
• Immersion. For probe work, say what depth is used in service; a certificate at 150 mm does not describe a probe used in a 60 mm thermowell.
• A spare, or a documented gap. Turnaround is weeks more often than days, and coverage that cannot lapse needs a second instrument planned in advance.