HT instruments HT157 - Manual (Page 39)

HT155 - HT157
EN - 37
6.1.3. ACOUSTIC CALIBRATION WITH CALIBRATOR HT151
CAUTION
 For the first acoustic calibration of the instrument’s microphone, set the
sound pressure level (SPL) according to the values allowed by the portable
calibrator HT151 (94.0dB and 114.0dB). For values different from these
reference values, program the instrument as described in § 6.1.2
 The portable calibrator HT151, which can be used to calibrate the sensitivity
of the microphones, guarantees a very steady performance level, compliant
with standard IEC 60492:2003 in Class 1
1. Turn on the instrument and select any operating mode, and wait for a few seconds until
it reaches the operating temperature
2. Use the “ ” or “ ” to select the “Calibrate” icon and confirm with “ ” to enter the
calibration mode (see Fig. 35)
3. Set the value of the sound pressure level to 94.0dB or 114.0dB according to the values
available on the calibrator HT151 (see § 6.1.2 – Line 4) as follows:
 Use the keys “ ” or “ ” to select “Mod.” and confirm with “
”. The “Mod” field
appears highlighted
 Use the “ ” or “ ” keys to move the cursor to Line 4 and the “
” or “ ” keys to
define the value in steps of 0.1dB. Press and hold the keys for an increase/decrease
in steps of 1dB. Accordingly, also the “App” field is highlighted
 Move the cursor to the “App” field and press “
” to confirm the value
4. Insert the lower part of the portable calibrator HT151 into the ½” microphone of the
instrument until a click is heard (see Fig. 36)
Fig. 36: Insertion of the calibrator HT151 into the instrument