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.