5
Figure 3
. Calibrating the Q-300 Microphone Sensitivity.
1.3 Calibration
Although the Q-300 will maintain accurate calibration over a long period of time, the calibration should be checked
before each use. To check the calibration of the Q-300, perform the following procedure using a Quest calibrator.
1.
Check that the LOBAT indicator is not on, indicating a weak battery.
2.
Turn the calibrator ON. If optional, set the frequency to 1 kHz. Note the SPL of the calibrator. Make sure that
the calibrator output is within the measuring range to which the Q-300 is currently set.
3.
Insert the microphone fully into the calibrator adapter ring, if required for the size microphone in use.
4.
Slowly place the calibrator onto the adapter/microphone.
5.
Press LEVELS. Use the
ª
or
«
keys to set the Q-300 to read SPL. The display should read the proper level
within 0.5dB.
6
NOTE: Most calibrators are affected by changes in altitude and barometric pressure. The rated SPL is set at standard
barometric pressure at sea level (760 mm Hg). Consult your calibrator manual for correction factors.
Storing the Calibration Value
The Q-300 can store the time, date and SPL of a calibration, which will be included in the printout and in downloaded
data for each study. If there is data in memory the unit must be RESET prior to performing a calibration (see page 12). To
perform a calibration, enter the following key sequence:
The CAL annunciator in the display will light, and the number in the display should match the output level of the calibrator. (To
change this value, refer to section 3, Setup Menu.) Connect the microphone to the calibrator as directed in steps 2,3 and 4 of
the previous section. Press RUN to begin the calibration routine. The display will read " CAL " and, after a few seconds, return
to the previous CAL display. The calibration SPL, time and date are now stored. If the calibration fails, " FAIL " will appear in
the display.
NOTE: When RUN is pressed to store the calibration value, A weighted SPL and C weighted SPL are measured and set equal
to each other. The unweighted logging peak detector is also calibrated, setting its output at 3dB above the RMS level
shown in the display. The Q300 must be calibrated at a frequency of 1kHz, as this condition is only true at 1kHz (and
6.2kHz).
As the peak detector is most accurate over the upper portion of the range, the calibration value should be in the
upper 40dB of the range used for calibration. It is important to not disturb the microphone during the calibration
routine, as this may cause a high peak reading and result in bad peak data.
The dosimeter will maintain its accuracy for many months of use. However, it is recommended that the dosimeter be
returned annually to a Quest Authorized service station for a recalibration.
Calibration standards, traceable to the National Institute of Standards and Technology (NIST) are maintained and used by
Quest.