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   TETRA PCs are designed to meet the needs of mobile enterprise users, while providing rugged features that protect and extend the system's lifespan and enhance reliability.
HOW RUGGED IS RUGGED? As the portable computer market evolves, an ever growing number of vendors claim to have "ruggedised" computers. As such how can decision makers tell how rugged a computer really is? - Truly rugged computer devices are engineered, inside and out, to operate in a range of hostile environments. Their design encompasses the external housing, internal components, special coatings, and seals amoung others allowing them to function correctly in operating environments ranging from challenging to extreme.
- Mobile workers that are required to operate outside of a controlled office environment are ideal candidates for a rugged PC.
Customers have to rely on a product's specifications and warranty statements to evaluate the amount of ruggedisation included in the product's design. Since specifications vary from product to product a number of ratings and standards established by various government agencies and industry associations such as the Military Standards for Environmental Testing (MIL-STD-810F) are available to help even out the evaluation process and provide a better assessment of a product's ruggedisation. Because certain ratings, standards and test methods are subject to interpretation closer scrutiny of a vendor's claims is recommended. To clearly understand a device's ability to perform where it will be used it is important to obtain detailed testing information (validated by an independent body) and warranty statements from the manufacturer to verify a product's ability to operate in those environments. Below is a summary of the key standard and tests as published by the U.S. Department of Defense for the MIL-STD-810F specification. UUT is the anacronym for the Unit Under Test. | Characteristic | Requirement | Test Method | Unit Status | | Transit Shock | 48 inch drop, concrete, all surfaces, edges and corners (26 drops) | MIL-STD-810F Method 516.5 | Test must be conducted while the UUT in ON (w/ HDD @ idle). Permanent loss of function is not acceptable. |
Shock
Truly rugged products should have correlating mechanical and crash shock specifications that define the device's ability to withstand the shock of an impact (repetitive) or collision (particularly if mounted in a vehicle). These types of shocks affect the computer's performance while operating and are conditions that users commonly encounter in the field. If the mechanicla and/or crash shock specifications are not clearly stated, or are less than below, in a product's specification then said prodcut's shock specification should be questioned. | Characteristic | Requirement | Test Method | Unit Status | | Mechanical Shock | 20g, 11ms, Terminal Sawtooth, Operating
40g, 11ms, Terminal Sawtooth, Non-Operating | MIL-STD-810F Method 516.5 | Test must be conducted while the UUT is operating. Loss of critical function is not acceptable. | | Crash Shock | 75g, 11ms, Terminal Sawtooth | MIL-STD-810F
Method 516.5 | test conducted while the UUT is non-operating in the vehicle mount. Loose, protruding or hazardous parts are not acceptable. |
VibrationTruly rugged products should have correlating vibration specifications that define the device's ability to withstand the constant effects of vibration (particularly if mounted and operated in a vehicle). Recurring vibration affects the computer's performance while opearting and is one of the leading conditions resulting in system failure. If the vibration specificationsa re not claerly stated, or are less than below, in a product's specification then said product's vibration specifciation should be questioned. | Characteristic | Requirement | Test Method | Unit Status | | Vibratiion (Integrity) | Minimum Integrity Test
0.04g^2/Hz, 20Hz - 1000Hz
-6dB/octive 1000Hz - 2000Hz
Figure 514.5C-17 | MIL-STD-810F Method 514.5 | Test must be conducted while the UUT is operating. Temporary, intermittent or permanent loss of function is not acceptable. | | Vibration (Vehicle) | Composite Wheeled Vehicle
Figure 514.5C-3 | MIL-STD-810F
Method 516.4 | Test must be conducted while the UUT is operating. Temporary loss of function is acceptable only if recovery is automatic and does not erquire user intervention. |
EnclosureTruly rugged products should have correlating enclosure class specifications that define the device's ability to withstand the effects of contaminants such as dust and moisture and other detrimental conditions such as solar radiation and salt fog. Taken together these specifications allow a product to properly function in a variety of harsh environments and protect the internal components from damage. If the enclosure specifications are not clearly stated, or are less (or omitted) than below, in a product's specifications then said product's enclosure class specifciation should be questioned.
| Characteristic | Requirement | Test Method | Unit Status | | Relative Humidity | 0% to 95% (+3/-5%)
non-condensing,
23ºC to 60ºC,
10 cycles of 48 Hr | MIL-STD-810F Method 507.4 | Test must be conducted while the UUT is operating. Ingress of moisture is not acceptable | | Solar Radiation | 1120 W/m2 (355 Btu/ft2/hr) UVB
@ 50oC, 7x24 ;hr cycles | MIL-STD-810F
Method 505.4 | Test must be conducted while the UUT is non-operating. Fading or degradation of material is not acceptable. | | Rain | Blowing Rain
4"/Hr, 40mph Wind | MIL-STD-810F
Method 506.4 Procedure 1 | Test must be conducted while the UUT is operating. Ingress of moisture is not acceptable. | | Rain | Drip Proof
7 gal/ft2/hr | MIL-STD-810F
Method 506.4 Procedure III (Drip) | Test must be conducted while the UUT is operating. Ingress of moisture is not acceptable. | | Sand & Dust | Particle Size <149 mm,
10 ± 7 g/m3 particle density
1.5m/s to 8.9 m/s Wind Speed | MIL-STD-810F
Method 510.4 Procedure 1 (Blowing Dust) | Test must be conducted while the UUT is operating. Ingress of dust or sand is not acceptable. | | Salt Fog | 5% saline for 48 hr (12 hr. wet, 12 hr. dry, 2 cycles) | MIL-STD-810F
Method 509.4 | Test must be conducted while the UUT is operating. Fading or degradation of material composition is not acceptable. Ingress of moisture is not acceptable. | | Contamination by Fluids | Detergents, brake fluid, aromatic hydrocarbons | Verified by Analysis | Test conducted while the UUT is non-operating. Fading or degradation of material composition is not acceptable. | | (1) Immersion | Immerse system to 30 cm in water, wait for 30 minutes, verify no bubbles from unit | MIL-STD-810F
Method 512.4 Procedure 1 | Test must be conducted while the UUT is operating. Temporary, intermittent or permanent loss of function is not acceptable. |
TemperatureTruly rugged products should have correlating operating and storage temperature specifications that define the device's ability to withstand the effects of extremem temperature environments, especially when the device is used outside or mouonted in a vehicle. If the temperature specifciations are not clearly stated, or are less than below, in a product's specification then said product's temperature specification should be questioned. | Characteristic | Requirement | Test Method | Unit Status | | Operating Temperature | -20ºC to +60ºC | MIL-STD-810F
Method 501.4, 502.4 | Test must be conducted while the UUT is operating. Temporary, intermittent or permanent loss of function not acceptable. | | Storage Temperature | -40ºC to +75ºC | MIL-STD-810F
Method 501.4, 502.4 | Test must be conducted while the UUT is non-operating. Permanent loss of function not acceptable. | | Thermal Shock | < 1.5ºC <5ºC/min
-20ºC to +60ºC | Verified during temperature cycle testing above | Test must be conducted while the UUT is operating. Temporary, intermittent or permanent loss of function not acceptable. |
SummaryTo truly understand a computer's "ruggedness" decision makers need to understand both the specification definitions and how the vendor determined a particular product's specifications. Understanding a computer's ruggedisation specifciations is critical when purchasing a ruggedisation device. To aid in a real world application of these specifications the table below is presented: | Test | Real World Event | | Drop | The operator drops the computer from chest height (when holding the device in the crook of the arm) while collecting or processing data. The operator accidentally drops the computer while moving between work areas as part of a daily routine. | | Shock | The computer sustains unexpected force when mounted in a vehicle and that vehicle is involved in a collision or the computer is struck when in operation. | | Vibration | The computer is constantly shaken from the low level vibration associated with engine noise while mounted in vehicle (car, truck, fork lift) The computer is exposed to vibration extremes as part of everyday use ie. bumpy or unpaved roads, speed bumps etc. | | Sand, Dust and Moisture | The computer is used to complete mission critical tasks in varying environments that include rain or dusty works sites such as paper mills, industrial warehouses or construction sites. | | Temperature | The computer is used by operators in all kind of variable temperature environments for instance if may be left sitting mounted in a vehicle with summer sun beating in while the operator is at lunch. It must resume operation when the operator returns to the vehicle. The computer is used in frigid temperatures and must be ready to function when need by the operator. | | Thermal Shock | On a summer day the computer is moved from the loaded dock into a freezer for a duration of time then moved back to the outdoors. |
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