The phrase "proper calibration" means making sure something is set correctly or adjusted accurately so that it functions or works as intended. Full definition
Systematic errors in scaling (such as XBT issues with speed of descent for ocean heat content) can be identified by proper calibration and cross comparison with other measures such as ARGO - and once found they can be corrected to produce a consistent and accurate record. (skepticalscience.com)
In rare cases, for example, the signal from a gamma ray may approach the expected signal of a dark matter particle, and proper calibration helps to rule out similar false positive signals. (sciencedaily.com)
(1) Your QAP must specify the methods used to perform external calibration checks on the EBT, the tolerances within which the EBT is regarded as being in proper calibration, and the intervals at which these checks must be performed. (transportation.gov)