Which of the following does not require a minimum of annual third party calibration?

• A. Analytical balance
• B. Drying oven
• C. Autoclave
• D. Set of weights

Answer: (D)

The main idea here is how often different lab tools need independent, third-party calibration based on how directly their readings affect measurements and safety. A set of weights is a calibration standard whose job is to verify or calibrate other instruments (like a balance). Because weights are physical references with very stable mass and often come with manufacturer-certified documentation, their own accuracy is typically maintained by those certificates and routine checks, rather than requiring annual external calibration as a rule. In practice, you verify weights against the certificate and, if needed, re-certify them, but they’re not treated the same as instruments whose measurements directly drive critical processes.

Analytical balances, drying ovens, and autoclaves are instruments whose performance directly impacts measured mass, temperature, and sterilization conditions, respectively. To ensure traceability and compliance, these often require periodic external calibration or validation by a recognized calibration lab on an annual basis.