LAB-EL Humidity Calculator
LAB-EL Humidity Calculator is a program for Windows system used to convert various physical quantities that characterize the microclimate. One of the most common cases is the calculation of the relative humidity of the air based on the knowledge of two other measurements: air temperature and dew point temperature or frost temperature when performing tests of the hytherographs in a climatic chamber, where reference devices are a precise thermometer and a reference dew point hygrometer.
At the dew point or frost temperature below zero, the results of air relative humidity calculations are significantly dependent on the correctness of determining whether the hygrometer mirror is dew or frost. Therefore, in order to calculate the relative humidity of the reference in the negative temperature range, for the case of obtaining a reference hygrometer of the frost condensate on the mirror, determine the reference relative humidity in accordance with the WMO (World Meteorological Organization) guidelines. For this purpose, the computer program LAB-EL Humidity Calculator in version 1.40 should be used during calculations, in which for the negative temperatures indicated by the dew point hygrometer it is necessary:
- for the case of frost on the mirror to select the “WMO” option,
- and for the case of dew (subcooled water) on the mirror to select the “Over water” option.
Measurements of the dew point hygrometer in the presence of dew condensate on the mirror (subcooled water) are not recommended when measuring for subzero temperatures due to the metastable nature of the condensate and uncertainty that this is supercooled water. Most often it is a multiphase mixture. In order to eliminate doubts related to the identification of condensate type of dew or frost, it is recommended to always obtain frost in hygrometers of the dew point by adequate high sub-cooling of the mirror before measurement.
