The document specifies testing procedures for determining calibration error for radiosonde humidity sensors sampled from mass production batches based on varying the levels of relative humidity at atmospheric upper-air temperatures using a laboratory setup. This document provides:

1. technical requirements for a laboratory setup to evaluate the calibration errors of radiosonde humidity measurement;
2. a test procedure for evaluating calibration error of radiosonde humidity sensors for a temperature range¹⁾ of −90 °C to 35 °C and for a relative humidity of 1 %rh to 100 %rh. Note, this document, is based upon relative humidity calculated by the percentage of water vapour pressure divided by saturation water vapour pressure over liquid water, not over ice, even at temperatures below 0 °C; hence, the maximum relative humidity is less than 100 %rh below 0 °C;
3. a method for evaluating the uncertainty for the measured radiosonde humidity calibration errors.