5. GENERAL
LABORATORY TEST METHOD GUIDELINES.
NOTE: Safety is an
inherent concern in all test programs. Specific concerns are addressed in appropriate
test methods. Guidelines for establishing a materiel safety program are in MIL-STD-882.
5.1 Standard Ambient
Test Conditions.
When the term "standard ambient" is specified in the methods of this standard,
use the values shown below. If the term is not used and no specific values are
called for in the test method or the materiel specification, conduct item tests
(e.g., pre-, during, and post-test)
at standard ambient conditions.
NOTE: Every effort has been made to use metric units throughout this document.
The initial figures are followed by U.S. units in parentheses, but these conversions
are not usually repeated throughout this document.
5.2 Tolerances
for Test Conditions.
Unless otherwise specified, adhere to the test condition tolerances shown
below for the following parameters. Any tolerance shown as ±X following a specified
value is intended to mean the specified value is what is intended
but, because of instrumentation
or measurement inaccuracies, a slight deviation
is acceptable but not outside of the tolerance.
(2) For required temperatures greater than 100°C, the temperature tolerance
can be ± 5°C. Specify the actual tolerance achieved.
Temperature:
25°C ± 10°C (77°F ±
18°F)
Relative
humidity:
20 to 80%
Atmospheric
pressure:
Site pressure
a. Test section air temperature. Surround the test item totally by an envelope
of air (except at necessary support points), considering boundary effects. Keep
the air temperature uniform in the immediate vicinity of the item. To ensure
that the test item is bathed in the required air temperature, place verification
sensors at representative points around the entire item and as
close to the test item as possible but not so the airstream temperature is affected
by the test item temperature. Keep these temperatures within ± 2°C (3.6°F) of
the required test temperature. Ensure the air temperature
gradient across the item does not exceed 1°C (2°F) per meter
or a maximum of 2.2°C (4°F) total (test item nonoperating). Wider temperature
tolerances are acceptable in situations such as:
(1) For large items with a volume greater than 5 m3, the temperature tolerance
can be ± 3°C. Justify any larger tolerance and obtain approval for its use
from the procuring activity.
b. Pressure. ±5 percent of the value or ±200 Pa, whichever is greater.
c. Humidity. Keep relative humidity at the chamber control sensor to ±5 percent RH of the specified value.
d. Vibration amplitude.
| Sinusoidal | ±10 percent |
| Random | See method 514.5 |
e. Vibration frequency. Measure vibration frequency of 25 Hz and above to an accuracy of ±2 percent. Below 25 Hz, use ±½ Hz.
f. Acceleration. Measure acceleration (g's) within 10 percent of the specified value.
g. Time. Control time (e.g., test durations and data gathering intervals) within 1 percent of the specified value for total test durations greater than 8 hours and within 5 minutes for durations or intervals of 8 hours or less, unless the nature of the test requires greater accuracy.
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