Larson Davis CAL150 Manual - page 12
CAL150 Technical Reference Manual
Microphone Calibration
2-6
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 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.
If the CAL150 is being used to calibrate several instruments,
then the history of calibration adjustments can usually
pinpoint which instrument is drifting. If all the measurement
instruments are drifting in the same direction by an amount
you consider significant, the CAL150 should be recertified.
If several instruments and several calibrators are in use, then
the history of calibration adjustments would precisely
pinpoint any problem pieces of equipment. Furthermore, it is
probably satisfactory to recalibrate only one of the
calibrators each year.