HT instruments HT157 - Manual (Page 40)

HT155 - HT157
EN - 38
5. Press and hold the “ON” key on the calibrator HT151 to activate the level equal to
94.0dB, looking at the activation of the red LED on the calibrator. Press and hold both
“ON” and “+20dB” keys to activate the level equal to 114.0dB. Preliminarily check the
emission of the output sound of the calibrator. Otherwise, replace the internal battery
(see §
6. Select the “Cal.” option on the instrument (see Fig. 35) and press the “ ” key to
activate calibration, which takes 10s
7. Press and hold the key(s) on the calibrator and look at the count of the seconds from 0
to 9 in the left-hand top part of the instrument’s display. In the lower part of the display,
the indication “LpC” indicates the applied sound pressure level, approximately equal to
the difference between the value provided by the calibrator and the free-field correction
of the microphone, while “Lpx” indicates the current sensitivity level of the microphone
8. Move the cursor to the “App.” option and press the “ ” key to save the new sensitivity
level of the microphone in the memory
9. If the difference between the previous sensitivity level and the new level measured with
calibration is > 3dB, for a few seconds the instrument shows the message “The
difference between these two sensitivity is too large! Please affirm the calibration is
correct!” If so, repeat the calibration procedure and, if necessary, contact the customer
service, as the microphone could be damaged
10. Remove the calibrator HT151 from the instrument. The calibrator turns off automatically
when releasing the “ON” key
6.1.3.1. Replacing the calibrator battery
LEGEND:
1. Metal cover of battery compartment
2. “ON” key to turn on the calibrator and
red LED
3. “+20dB” key to activate the sound
pressure level of 114.0dB
4. Adapter for the insertion of a ½”
microphone
5. Internal cavity of the calibrator
Fig. 37: Replacing the calibrator HT151 battery
1. Fully unscrew the metal cover of the battery compartment
2. Extract the battery from inside the calibrator
3. Replace the battery with an equivalent one (see § 10.4)
4. Restore the metal cover of the battery compartment into place and screw it in