A useful initial step to remove enclosure moisture is to define the enclosure environment utilizing a temperature/humidity data logger. These inexpensive, battery-powered devices (~$200) record Dry Storage Cabinets. They also indicate the dew-point conditions inside the enclosure (Fig. 6). Maintaining enclosure temperatures above dew-point temperatures is a requirement for condensation prevention.
Pursuing this alternative can be accomplished in a quantity of ways, starting from desiccant to thermoelectric dehumidifiers-the task is to select a choice that is inexpensive to both implement and maintain. This type of water-absorption ability of desiccant is influenced by a number of factors (e.g., desiccant type, humidity, temperature). For example, silica gel can absorb as much as 40% of its weight in water. A 4’ x 6’ x 2’ electrical enclosure in a hot/humid environment would saturate 125 g of desiccant in about two air exchanges. Therefore, the resulting frequency of required desiccant change-outs (which affects maintenance costs) is basically driven by how well the enclosures are sealed. Unfortunately, when it comes to desiccant regimes, each act of opening an enclosure to examine the desiccant serves as an air exchange.
Dehumidifiers are comparatively cheap, although finding convenient available power inside an enclosure may be problematic. The positive feature is that dehumidifiers eliminate the manual intervention connected with a desiccant regime. The negative feature of dehumidifiers is that they introduce one more piece of equipment that can ultimately fail.
Another technique is to minimize the potential for condensation through internal heaters (or light bulbs) to help keep the internal enclosure temperature well above dew-point temperatures. The down-side is the fact that higher temperatures may be detrimental to a few heat-sensitive electronic components, and also the higher temperature actually allows the air to hold more moisture. Venting and fans can help avoid condensation in certain situations-although the Dry Storage Cabinets For Optics still exists. One interesting product the designers of GORE-TEX® have produced involves screw-in vents which allow enclosures to breathe, while providing a barrier to moisture and contaminants. The idea behind this kind of venting is it decreases the stress on door seals when you can find pressure differentials between the enclosure and the environment. By equalizing pressure, the possibility of moist air at higher pressure defeating your home seals is lessened.
Moisture-hardening of electronics includes a variety of techniques. With regards to connectors, using waterproof connectors or hardening existing connectors and splices with heat-shrink tubing can be of use to reduce water intrusion and corrosion. Avoiding horizontal orientation of components like printed circuit boards inside the enclosure can minimize surfaces where condensation may collect for extended time periods. Conformal coatings for lower-voltage printed circuit boards and the use of potting (see Fig. 7) of higher-voltage components greatly boost the moisture resistance of components. Potting costs vary according to the dimensions of order, material selection jmmhra part geometry, but representative costs for very small orders (less than 10) typically fall in the range of $18 to $45 per part. An extra benefit from potting is the added defense against shock and vibration.
Moisture protection of electronics is most beneficial approached by pursuing practices that maximize Dehumidifying Dry Cabinets during equipment installation, coupled with being ready to mitigate failure through anyone moisture-protection measure during operations. This strategy, along with tracking equipment-maintenance performance to understand how well moisture-protection measures will work, can lead to long-term minimization of electronics moisture-induced problems. MT.