A helpful initial step to eliminate enclosure moisture is to characterize the enclosure environment using a temperature/humidity data logger. These inexpensive, battery-powered devices (~$200) record Low Humidity Control Cabinets. They also indicate the dew-point conditions in 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 quantity of ways, ranging from desiccant to thermoelectric dehumidifiers-the task is always to select an alternative that is certainly inexpensive to both implement and keep. Water-absorption ability of desiccant is dependent on a variety of factors (e.g., desiccant type, humidity, temperature). As an example, silica gel can absorb up to 40% of their 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 largely driven by how well the enclosures are sealed. Unfortunately, when it comes to desiccant regimes, each act of opening an enclosure to inspect the desiccant may serve 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 yet another device that can ultimately fail.
Another strategy is to reduce the potential for condensation through internal heaters (or light bulbs) to keep the inner enclosure temperature well above dew-point temperatures. The down-side is that higher temperatures may be detrimental to some heat-sensitive electronic components, as well as the higher temperature actually allows the air to hold more moisture. Venting and fans can aid in avoiding condensation in certain situations-even though Dry Cabinets For PCB Storage 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 theory behind this sort of venting is it reduces the stress on door seals when there are pressure differentials in between the enclosure as well as the environment. By equalizing pressure, the possibility of moist air at higher pressure defeating your door seals is lessened.
Moisture-hardening of electronics includes a number of techniques. In terms of connectors, using waterproof connectors or hardening existing connectors and splices with heat-shrink tubing can be useful 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 periods of time. Conformal coatings for lower-voltage printed circuit boards and using potting (see Fig. 7) of higher-voltage components greatly boost the moisture resistance of components. Potting costs vary based on the size of order, material selection jmmhra part geometry, but representative costs for really small orders (less than 10) typically fall inside the range of $18 to $45 per part. Yet another advantage of potting is the added defense against shock and vibration.
Moisture protection of electronics is best approached by pursuing practices that maximize Dehumidifying Dry Cabinets during equipment installation, coupled with being prepared 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.