Environmental considerations for rugged PC's


Care in choosing a suitably rugged computing platform, be it a Notebook, Tablet or portable "lunch-box" Chassis, is crucial where it is envisaged the system is to be used outside the relatively benign environment of the office. A set of ratings have been produced to fix some definable standards so that a judgement can be made as to the suitability of a particular computer system to a task and are most commonly are defined in two forms:-

  1. MIL (military) STD 810E/F testing protocols for resistance to rain, humidity, salt fog, sand/dust, vibration, shock and temperature.

  2. IP (Ingress Protection) testing which establishes the ability of an electrical enclosure to withstand penetration from solids (sand/dust) and liquids.

Drop test rig - showing procedure for MIL 810E/F


The military standard MIL 810E and F (F superseded E in January 2000) is a broad range of testing protocols but from which is selected the most relevant to match the enviromental challenges for a particular piece of equipment. The broadness of choice does make it difficult to place in a nutshell all the various aspects of this stringent standard, but as an example we can concentrate on the its most relevant application to portable rugged PC's; that is the drop test. The MIL-STD 810E/F specification for mechanical shock calls for portable computers such as tablet or notebook PC's to withstand 26 drops, (one drop on each face/edge/corner with display screen closed, and unit powered off), onto 2" thick plywood over solid concrete from a height of metre - without functional failure. A computer successfully completing such a test is certified as MIL-STD 810E/F compliant in this respect.

In the real world this set of circumstances will be unlikely to be repeated, but it does give a good indicator as to the suitability and likelihood of survival, after all many off-the shelf high street computer systems can barely survive the general knocks in the office, let alone any kind of drop. Possessing a PC system with a MIL specification also means that physically the system should have a longer life. A high resilience to vibration is frequently another testing protocol applied, as in real life portable PC's can be used inside and alongside machinery or a vehicle.



IP rating describes the ability of an electrical enclosure to withstand penetration from solids and liquids, in real life most commonly dust and rain water. With electronic equipment choosing a suitable IP level is a critical factor. Below is a table that defines the levels. The first digit indicates the level of protection that the enclosure provides against access to hazardous parts/particles, the second harmful ingress of water. So for example IP67 gives complete protection from all solid particulates (6) and withstand temporary water immersion to 1 metre (7).

Ingress protection levels
Num.PROTECTION FROM SOLIDSPROTECTION FROM LIQUIDS
0No protectionNo protection
1Protection from objects greater than 50mm in diameter. (e.g. the hand)Vertically dripping water and external condensation
2Protection from objects >12.5mm in diameter (e.g. fingers)Dripping water to an angle of 15 degrees from the vertical
3Protection from objects with a diameter > 2.5mm ( e.g. tools and wires)Water splash and low pressure spray up to 60 degrees,limited liquid access allowed but not as to affect operation.
4Protection from entry by solid objects with a diameter > 1.0mm Water splash and low pressure spray all angles, limited liquid access allowed but not as to affect operation.
5Protection from dust, though limited ingress is allowed as long as volume does not affect operation.Low pressure water jets all directions
6Complete protection from all solid particulatesProtection from powerful jets of water (e.g. as found on the deck of a ship)
7Not applicableTemporary (30 minutes) complete immersion at 0.15 to 1 metre
8Not applicablePermanent immersion. Depth to be pre-defined on a per case basis

If the PC system is to be used where there is any risk of liquid or dust contamination then choosing a system with a rating of at least IP54 is advisable. Such a rating will allow its use outdoors in the field environment, repelling rain water and wind borne dust to a high degree. However where it is envisaged the system is to be used for several hours in heavy blowing rain or on the exterior deck of a ship a higher IP65 or 67 level should be considered.

We hope the above description has proven informative, however as it is just an overview do feel free to contact DataQuest Solutions should you have any queries.

Links
More information on the MIL standards can be found here; http://en.wikipedia.org/wiki/MIL-STD-810
For IP code standards; http://en.wikipedia.org/wiki/IP_Code


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© DataQuest Solutions Ltd 2005
Last modified 05.03.2013