BRUEL & KJAER 4226 User Manual page 30

22 Multifunction Acoustic Calibrator Type 4226 – User Manual
3.8.1 Crest Factor (= 3) Check Using the Coupler
The instructions below use a sound level meter as the instrument under test. The principal,
however, applies in general.
Ensure that both Type 4226 and the sound level are switched on.
1) Set up the sound level meter as follows:
a) Set to measure SPL (sound pressure level).
b) Set the dynamic range to a range that will prevent overload at 114 dB SPL.
c) Set the frequency weighting to Lin or aW.
d) Set the time weighting to Fast or Slow.
2) Fit the coupler onto the microphone of the sound level meter, press it down gently until the
microphone is properly seated against the stop in the coupler. Ensure that the coupler is
properly connected to Type 4226.
3) Set up Type 4226 as follows:
a) Set the
Function
4) The 2 kHz LED on Type 4226 will light up. This is the recommended frequency setting for this
test.
5) When conditions are stable, note the reading displayed on the sound level meter, if necessary
rotate the knurled wheel on Type 4226 until a convenient value is displayed.
6) Move the
Function
error) in the reading shown on the sound level meter. Compare this with the values shown in
Table 3.5.
7) Repeat if required for other frequencies. Note the crest factor of the test signal is assured only
for the preselected frequency (2 kHz) and above.
3.8.2 Crest Factor (= 10) Check Using the AC Out Socket
The instructions below use a sound level meter as the instrument under test. The principal,
however, applies in general.
✐
You will need the following optional accessories: Input Adapter JJ-2614 and Coaxial Plug
Please note:
JP-0144.
Ensure that both Type 4226 and the test instrument off before starting.
1) Carefully unscrew and remove the microphone of the sound level meter and put it in a safe
place, for example, its transport box.
2) In place of the microphone, screw on an Input Adapter JJ-2614 and make a connection from
here to the AC Out socket of Type 4226 using Coaxial Plug JP-0144.
3) From here on follow the instructions given in section 3.8.1 above, omitting step 2.
switch to Test Level. This will enable the
switch on Type 4226 to Crest Factor and note any change (which is an
buttons.
Frequency Step