(b) When the technical publication for a specific measurement
standard or TMDE provides information for temperature compensation, i.e.,
correction factors, those instruments may be calibrated or used to
calibrate. The temperature-compensating procedures for the instrument must
be used.
(c) When the approved technical publication for a specific
measurement standard or TMDE specifies a temperature operating range that is
within the existing uncontrolled temperature of the laboratory, the
instrument may be calibrated or used to accomplish calibration. Table 1 is
a partial list of measurement standards and TMDE with an extended
temperature operating range.
Instruments listed in Table 1 have an
operating range of 5C (9 F) and 10C(18F).
(d) When the laboratory temperature exceeds the specified limits,
the temperature of the laboratory must be returned to and stabilized within
the required limits.
The time necessary to stabilize the laboratory
temperature is dependent on a number of variables and cannot be estimated
here.
It is not only the temperature of the laboratory that must be
stabilized, but also the temperature of the instruments within the
laboratory.
Before normal calibration operations can be resumed, the
temperature of the instruments must be within the nominal calibration (or
operating) temperature stated in the technical publication for the
instruments (TM, TB, manufacturer's manual, etc.). Table 2 may be used as a
guide to determine the temperature recovery stabilization time for the
instruments listed.
This table can also be used for other instruments of
the same type and constructed in a similar manner.
Table 2 includes
instruments that are AACL measurement standards and others that are not.
The fact that an instrument appears on this list does not mean that the
instrument must be used in an ambient temperature of 23 C€1C. Technical
publications (TM, TB, manufacturer's literature, etc.) must be consulted to
determine the ambient temperature in which the instrument may be used to the
required accuracy. Through the use of this table, it can be determined how
long it will take an instrument to return to the nominal calibration (or
operating) temperature specified by the manufacturer.
(e) Shutdown.
In the event of interruption of operations for
extended periods due to equipment repair, structure repair, etc., the air
conditioning equipment (cooling, heating, filtering) will be operated
continuously for a minimum of 24 hours prior to resuming operations.
TB
750-117/TB 750-25 contain criteria for governing instruments with very great
temperature lag.
When suspending operation of the air conditioning
equipment, standards and instruments will be protected from deterioration
caused by dust, dirt, moisture, and other contaminants that may enter the
laboratory.
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