ENVIRONMENTAL CONSIDERATIONS

The physical environment of a product plays an important role in the cost, performance and longevity of a product.

STABILITY VERSUS AMBIENT TEMPERATURE

Most integrated circuits used in electronic design are available in three temperature ratings. The higher the temperature rating the more costly the circuit.

Commercial circuits are typically rated for use in the 0 to 70 Deg C temperature range

Industrial circuits are typically rated for use between –25 to 85 Deg C. However -40 to 85 Deg C circuits are becoming more common.

Military or Mil Spec circuits are typically rated for use between -55 and 125 Deg C.

The temperature coefficient of resistors, capacitors, voltage regulators, and reference voltage circuits all have to be matched to meet the overall temperature stability specification of the product.

As the temperature range increases, all of these parts have to be selected to meet specifications. The cost increases proportionally.

Location of the product, if possible, should be chosen to limit its exposure to wide fluctuations in ambient temperature.

PHYSICAL CONSIDERATIONS

Humidity, if high enough to condense liquid on the circuit boards of a product, may require circuit boards to be conformally coated.

Wet operating areas may require a product that meets a hose down requirement (Nema 4). Weatherproofing may be required.

Caustic atmospheres may require all stainless hardware and protection for other materials in the product.

Dust, especially conductive dust, may require dust proof packaging.

Solvents used around the product may dictate packaging materials that are solvent proof.