Trimble MCS Hardware Test Standards
Trimble Mobile Computing Solutions Division puts all of its rugged handheld computers, and even many accessories through a series of internationally-recognized and certified tests to ensure that they can handle extreme weather conditions, dust, drops, water spray and submersion – and more. This section explains the various standards we adhere to.
Trimble handhelds meet rigorous MIL-STD-810G standards for drops, vibration, humidity, altitude and extreme temperatures. These standards are maintained by the United States military, with the U.S. Army Test and Evaluation Command (ATEC). The MIL-STD-810 test series are provided by the United States Department of Defense (DoD) and are widely adopted for commercial products as they are independently verified.
This standard describes a system for classifying the degrees of protection provided by the enclosures of electrical equipment, such as ruggedized handheld computers. The adoption of this classification system, wherever possible, will promote uniformity in methods of describing the protection provided by the enclosure and in the tests to prove the various degrees of protection. The IEC Technical Committee prepared this standard. Elements of the IP Code and their meanings
MIL-STD-810G Immersion in Water
Temperature differential between the test item and the water can influence the outcome (leakage) of an immersion test. Increasing the test item temperature above the water temperature for the immersion test usually includes heating of the test item to establish a pressure differential (while cooling) to determine if the seals or gaskets leak under relatively low-pressure differential, and to induce expansion/contraction of the hardware. Although desired, establishing a specific temperature differential for fording tests is often impractical due to the size of the hardware
How Trimble Tests for Immersion: The minimum requirements to pass the immersion test are heating a unit for one hour to a core temperature of 49 °C (120 °F). Within one minute after the removal from the heat source, the device is plunged into 22 °C (72 °F) water to a depth of 1 meter, and kept there for 30 minutes. The unit must function properly at completion of test to pass.
MIL-STD-810G Sand & Dust
This test method is divided into two procedures.
- The small-particle procedure (dust, fine sand) is performed to determine the ability of the equipment to resist the effects of dust particles that may penetrate into cracks, crevices, and joints.
- The blowing sand test determines whether the hardware can be stored and operated under blowing conditions without experiencing degradation of its performance, effectiveness, reliability, and maintainability due to the abrasion (erosion) or clogging of large, sharp-edged particles.
Shock (commonly referred to as drop) tests are performed to assure that the hardware can withstand the relatively infrequent, non-repetitive shocks or transient vibrations encountered in handling, transportation, and service environments. Mechanical shocks will cause a piece of equipment to respond at both forced and natural frequencies. This response, among other things, can cause:
- Failures due to increased or decreased friction, or interference between parts
- Changes in dielectric strength, loss of insulation resistance, variations in magnetic and electrostatic field strength
- Permanent deformation due to overstress
- More rapid fatiguing of the hardware
Vibration testing is performed to determine the resistance of equipment to vibration expected in its shipment and application environments. Vibration can cause:
- Wire chafing
- Loosening of fasteners
- Intermittent electrical contacts
- Touching and shorting of electrical parts
- Seal deformation
- Component fatigue
- Display / Touch Panel misalignment
- Cracking and rupturing
- Excessive electrical noise
MIL-STD-810G High Temperature
High temperatures may temporarily or permanently impair the performance of the test item by changing the physical properties or dimensions. Examples of other problems that may occur as the result of high-temperature exposure include:
- Parts binding from differential expansion of dissimilar hardware
- Hardware changing in dimension, either totally or selectively
- Gaskets displaying permanent set
- Closure and sealing strips deteriorating
- Fixed-resistance resistors changing in values
- Electronic circuit stability varying with differences in temperature gradients and differential expansion of dissimilar hardware
- Transformers and electromechanical components overheating
- Shortened operating lifetime
- High pressures created within sealed cases
- Discoloration, cracking or crazing of organic hardware
MIL-STD-810G Low Temperature
Low temperatures have adverse effects on almost all basic hardware. Exposure of test items to low temperatures may either temporarily or permanently impair the operation by changing the physical properties of the hardware. Therefore, low-temperature testing must be considered whenever the item will be exposed to temperatures below standard ambient. Examples of some problems that may occur when exposed to cold temperatures include:
- Hardening and embrittlement of hardware
- Binding of parts from differential contraction of dissimilar hardware and the different rates of expansion of parts in response to temperature transients
- Changes in electronic components (resistors, capacitors, etc.)
- Stiffening of shock mounts
- Cracking and crazing, embrittlement, change in impact strength and reduced strength
- Static fatigue of restrained glass
- Condensation and freezing of water
MIL-STD-810G Temperature Shock
Temperature shock tests are conducted to determine if the hardware can withstand sudden changes in the temperature of the surrounding atmosphere without experiencing physical damage or deterioration in performance.
As a result of exposure to sudden temperature changes, operation of the test item may be affected either temporarily or permanently. Examples of problems that could occur as a result of exposure to sudden changes in temperature are:
- Shattering of glass
- Binding or slackening of moving parts
- Separation of constituents
- Stiffening of shock mounts
- Changes in electronic components
- Electronic or mechanical failures due to rapid water or frost formation
- Differential contraction or expansion of dissimilar hardware
- Deformation or fracture of components
- Cracking of surface coatings
- Leaking of sealed compartments
Moisture can cause physical and chemical deterioration of hardware to include corrosion and biologic growth; changes in hardware properties due to moisture penetration, and electrical or mechanical performance issues due to condensation. Typical problems that can result from exposure to a warm, humid environment include:
- Swelling of hardware due to moisture absorption
- Loss of physical strength
- Changes in mechanical properties
- Degradation of electrical and thermal properties in insulating hardware
- Electrical shorts due to condensation
- Binding of moving parts due to corrosion or fouling of lubricants
- Oxidation and/or galvanic corrosion of metals
- Loss of plasticity
- Accelerated chemical reactions
MIL-STD-810G Method Low Pressure/Altitude
Low-pressure (altitude) chamber tests are performed to determine if the hardware can withstand and operate in a low-pressure environment and withstand rapid pressure changes. Examples of some problems that could occur as a result of exposure to reduced pressure include:
- Rupture or explosion of sealed containers
- Change in physical and chemical properties of low-density hardware
- Erratic operation or malfunction of equipment resulting from arcing or corona
- Overheating of equipment due to reduced heat transfer
- Failure of hermetic seals
MIL-STD-810G Method Solar Exposure
With many computers, the heating effects of solar radiation are more taxing than material degradation. Computers are generally manufactured with metal enclosures. On the other hand, LCDs may suffer from both heating effects and material degradation. Coatings may degrade somewhat with color changes but the impact of plastic becoming brittle, for example, does not apply to a computer. A computer used outdoors can become very hot with the subsequent impact on keeping the internal components within operating temperature specifications.
The maximum surface and internal temperatures attained by materiel will depend on:
- the temperature of the ambient air.
- the intensity of radiation.
- the air velocity.
- the duration of exposure.
- the thermal properties of the materiel itself, e.g., surface reflectance, size and shape, thermal conductance, and specific heat.
Material can attain temperatures in excess of 60°C if fully exposed to solar radiation in an ambient temperature as low as 35 to 40°C. Paint color and composition can have a major impact on surface temperature.
810G Method 501.5 (High Temperature) mentions Method 505.5 as a factor to consider (Aggravated solar) when determining effects of high temperature. In addition, Method 503.5 (Temperature Shock) also references 505.5 in section 2.3.1 for ‘Climatic Conditions’.
The impact of solar radiation heating effects include:
- Jamming or loosening of moving parts.
- Weakening of solder joints and glued parts.
- Changes in strength and elasticity.
- Loss of calibration or malfunction of linkage devices.
- Loss of seal integrity.
- Changes in electrical or electronic components.
- Premature actuation of electrical contacts.
- Changes in characteristics of elastomers and polymers.
- Blistering, peeling, and de-lamination of paints, composites, and surface laminates applied with adhesives such as radar absorbent material (RAM).
- Softening of potting compounds.
- Pressure variations.
- Sweating of composite materials and explosives.
- Difficulty in handling.