The single-point rapid temperature change test chamber humidification process is actually to increase the water vapor partial pressure. In the 1950s, the initial use of the humidification method was to spray water on the test chamber wall, and the water surface saturation pressure was controlled by controlling the water temperature. The surface of the wall of the tank forms a large surface, and the relative humidity of the chamber is increased by adding vapor pressure to the inside of the chamber through diffusion. Since the control of humidity at the time was mainly a simple switch quantity adjustment using a mercury-electricity contact type conductivity meter, the adaptability to the control of the water temperature of the large delay hot water tank was poor, so the control transition process was long and could not meet the alternating damp heat The need for more humidification requirements, more importantly, when spraying on the wall, there is inevitably water droplets on the test sample to form different levels of pollution. At the same time there are certain requirements for the drainage inside the box. The single-point rapid temperature change test method was quickly replaced by steam humidification and shallow tank humidification. This method still has some advantages. Although its control transition process is long, the humidity fluctuation is small after the system is stable, and it is more suitable for a constant damp heat test. In addition, the heat of vaporization during humidification does not increase the extra heat in the system. Also, the spray water has a dehumidifying effect when the temperature of the spray water is controlled to be lower than the point temperature required by the test.
With the development of the damp heat test from the constant wet heat to the alternating wet heat test box, a relatively rapid humidification reaction capability is required, and when the spray humidification cannot meet the requirements, the steam humidification and the shallow tank humidification method are beginning to be adopted in large quantities and developed.
The single-point rapid temperature change test box relay is suitable for different central signal wiring modes. No cross-line is required to be connected to the positive or negative terminal of the power supply. The relay consumes very little power and does not require external resistors. The relay completely eliminates the traditional current differential principle and adopts the method of intelligent comparison of the current amplitude throughout the alarm cycle. It has a memory characteristic, that is, the amplitude of the current before the memory alarm current reaches the moment, comparing the current before and after the alarm current arrives The amplitude, if there is a long signal and a short signal overlap, within the delay period of the preview signal, as long as the long signal does not return, to ensure a correct alarm, the long signal will not be "erased" by the short signal. Temperature change test humidification method.