Larson Davis CAL200, Руководство пользователя

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CAL200 Technical Reference Manual Microphone Calibration 2-5
some precautions should be taken when sudden changes
occur:
• The temperature of the CAL200 should be stable. If the
temperature changes suddenly, provide a stabilization
time of at least 15 minutes. This will ensure that the
temperature compensation sensors are at the same
temperature as the rest of the unit.
• While humidity will not affect the CAL200, avoid
condensing moisture. Also, avoid environments over
90% relative humidity because condensation can easily
take place.
• The CAL200 is insensitive to magnetic fields. However,
the instrument being tested may not be. Therefore,
calibration should not be done near motors, dynamos,
high voltage wires, or other sources of electromagnetic
fields.
Calibrator Calibration
The American National Standards Institute states, “An
acoustical calibrator should be recalibrated at least annually
by the instrument manufacturer or an acoustical test
laboratory qualified to perform calibration.” (American
National Standards Institute. Specifications for Acoustical
Calibrators. ANSI S1.40, 2006, par. 5.2)
Larson Davis believes the frequency of recalibration
depends on the number of calibrators being used and the
number of instruments being calibrated. With this in mind,
the following guidelines are presented for your
consideration:
If a systematic drift of several dB
occurs, there is no reliable way to
verify which instrument is at fault,
even though it is more likely to be the
measurement instrument. • For one calibrator and one measurement instrument, the
CAL200 should be certified at least yearly.
• For one calibrator and several measurement instruments,
one calibration a year is recommended. but if no
systematic drift occurs, every two years might be
satisfactory.
• For several calibrators and several instruments, one
calibration a year is recommended.