MIL-DTL-6508C
4.5.3 Position error. Each thermometer shall be held in the level position and a reading
taken. It shall then (in level position) be lightly tapped and a reading taken. The instrument
shall then be held in the following positions:
a. Rotated from level position through 45 degrees to the rear (dial tilted 45 degrees
backwards from vertical position).
b. Rotated from level position through 45 degrees to the front (dial tilted 45 degrees
forward from vertical position).
c. Rotated from level position through 45 degrees to the right (dial vertical).
d. Rotated from level position through 45 degrees to the left (dial vertical).
e. Rotated from level position through 180 degrees (dial vertical).
The readings taken in the positions above shall deviate from the original reading by not more
than 1.0 °C.
4.5.4 Drift. The thermometer shall be subject to a temperature of 70 °C (158 °F) for a
period of one hour, after which the stem of the thermometer shall be immersed in a temperature-
controlled bath at 20 °C (68 °F) and the scale error observed. There shall be no change in the
scale error, over that obtained in the scale error tests (see 4.5.2) as a result of this test. In
addition, no failure of any kind shall occur.
4.5.5 Durability. The stem of the thermometer shall be alternately immersed in a bath
containing liquid at 40 ±2 °C (104 ±3.6 °F) and a bath containing liquid at -40 ±2 °C
(-40 ±3.6 °F) one hundred times, after which the scale error test shall be repeated. The change in
indication at the conclusion of the test shall not have increased by more than 1.0 °C over the
indications obtained as a result of the scale error test specified in the individual tests.
4.5.6 Response time (lag). The stem of the thermometer shall be quenched from a bath
at 40 °C (104 °F) to an agitated liquid bath at -40 °C (-40 °F). The time required for the
indicated temperature to fall from 40 to -30 °C shall not exceed 14 seconds. The test shall be
accomplished by immersing the thermometer stem to the attaching thread in a temperature-
controlled bath.
4.5.7 Sealing. The thermometer shall be immersed to a depth of 2 feet in water at room
temperature for a period of 2 hours, after which it shall be removed, dried, and inspected for
moisture leakage. Any appearance of moisture on the dial or inner surface of the cover glass
shall be cause for rejection.
4.5.8 Vibration. The thermometer reading shall be recorded at any temperature specified
in table II. The thermometer shall then be mounted on a suitably designed vibration stand and
subjected to vibration for a 2-hour period.
a. The vibration shall be such that a point on the thermometer case will describe, in a
plane inclined 45 degrees to the horizontal plane, a circle with a 0.018 to 0.020 inch diameter.
The vibration frequency shall be varied from 8 to 50 Hz and back for each hour of the test.
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