Design, construction and implementation of relative humidity and temperature climatic chamber for metrology laboratory

Abstract

For the calibration of thermohygrometers it is necessary to have a means of generating temperature and relative humidity for this reason in this development we will build a climatic chamber which will generate and control these two magnitudes. For the generation of temperature a thermoresistance was used and the decrease of relative humidity was done through a silica gel trap through which the air inside the chamber is recirculated with the use of a vacuum pump. On the other hand, an ultrasonic humidity generator also known as fogger was used to increase the relative humidity. For the construction of the chamber, acrylic was used as the main material, since it is translucent and facilitates the visualization of the thermohygrometers’ indications. For the control of the process variables such as temperature and relative humidity, an Arduino card was used, which through PWM pulse width modulation, the control was performed achieving a variation of 0.3 °C and 2 %RH, which will be evaluated by an accredited laboratory in the characterization of isothermal media certified by ONAC, since it is in this way that the inhomogeneity, stability and thermal load of the medium, components that affect the uncertainty of the instruments under calibration, are evaluated. It should be remembered that this development was carried out in order to create an air medium with which temperature and relative humidity measuring instruments can be calibrated in the metrology laboratory VALIDACIONES Y METROLOGIA LM S.A.S., since it is in the process of growth and one of its main objectives is to be accredited in the magnitudes of temperature and relative humidity before the accreditation body in Colombia (ONAC), which is the entity that will finally give the technical approval to release the chamber and put it into operation.