A good initial step to eliminate enclosure moisture is to define the enclosure environment utilizing a temperature/humidity data logger. These economical, battery-powered devices (~$200) record Dry Storage Cabinets. Additionally they 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 option can be accomplished in a number of ways, starting from desiccant to thermoelectric dehumidifiers-the challenge is always to select an alternative which is inexpensive to both implement and keep. The water-absorption capability of desiccant is influenced by many different factors (e.g., desiccant type, humidity, temperature). For example, silica gel can absorb up to 40% of the weight in water. A 4’ x 6’ x 2’ electrical enclosure in a hot/humid environment would saturate 125 g of desiccant in approximately two air exchanges. Therefore, the resulting frequency of required desiccant change-outs (which affects maintenance costs) is essentially driven by how well the enclosures are sealed. Unfortunately, in terms of 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 the fact dehumidifiers remove the manual intervention associated with a desiccant regime. The negative feature of dehumidifiers is they introduce an additional item of equipment that can ultimately fail.
Another technique is to reduce the chance of condensation through internal heaters (or light bulbs) to maintain the inner enclosure temperature well above dew-point temperatures. The downside 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 some situations-although the Moisture Control Cabinets still exists. One interesting product the makers of GORE-TEX® have produced involves screw-in vents that enable enclosures to breathe, while providing a barrier to moisture and contaminants. The theory behind this type of venting is it reduces the stress on door seals when there are pressure differentials between the enclosure and also the environment. By equalizing pressure, the chance of moist air at higher pressure defeating your home seals is lessened.
Moisture-hardening of electronics includes many different techniques. When it comes to connectors, using waterproof connectors or hardening existing connectors and splices with heat-shrink tubing can be of use to lower water intrusion and corrosion. Avoiding horizontal orientation of components like printed circuit boards within the enclosure can minimize surfaces where condensation may collect for longer amounts of time. Conformal coatings for lower-voltage printed circuit boards and the usage of potting (see Fig. 7) of higher-voltage components greatly increase the moisture resistance of components. Potting costs vary according to the dimensions of order, material selection jmmhra part geometry, but representative costs for tiny orders (lower than 10) typically fall within the range of $18 to $45 per part. An extra benefit of potting is definitely 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, along with being prepared to mitigate failure through any one moisture-protection measure during operations. This plan, together with tracking equipment-maintenance performance to know how well moisture-protection measures work, can lead to long-term minimization of electronics moisture-induced problems. MT.