......... LZ_ _ _ _. ,,
1. Set Calibrator ON.OFF switch to ON. A 1000 llz tone
should be heard,
2. Check battery indicating meter to he sure needle eaters into
the green "good battery" area. If needle stays in red area, replace
batteries.
3, {Skip this step if the microphone to be measured is 1-1/8
inch diameter.} Insert tile proper sized microphol_e adaptor, inner
rim down, into tile calibrator coupler cavity.
,t. Carefully insert the microphone into tile calibrator coupler.
Be sure microphone is down inside the coupler resting flash on the
lower coupler rial. If tile Model 2151t Sound Level Meter is used
with a microphone extensit_n cable, then calibration is performed
witb the microphone I_otlnted ell 1he extension cahle.
CAUTION
Ral_id insertion or withdrawal of the microphone may dam-
age the microphone or the transducer i_ the coupler because
of the rapid change in pressure on the diaphragms.
5. Proceed to verify the instrument accuracy by comparing the
110 dfi output level of the calibrator to tile instrument reading. Note
the correction ill calibrator output due to altitude effects given be-
low, Adjust the sound level meter sensitivity as necessary.
6, When calibration has been made, carefully remove the micro-
phone and turn calibrator to OFF.
BATTEItY REPI,ACEMENT
To replace batteries, remove two screws from face plate on
bottom of calibrator. Slide off fllce plah_ and outer shell to expose
batteries.
ALTITUI)E EFFECTS
Most calibrators including tile CA.12 are affected by altitude.
The transducer dinphram within the calibrator creates the sound as it
vibrates ilgainst tbe air. When the air is thinner (at higher elevations)
a lower sotlnd l_vel is Droducod,
The CA-12 is calibrated to produce ]:tO dB at sea level. When
the unit is operated above sea level a slightly lower sound level is
emitted depending oll altitude, For each 2000 feet of elevation above
sea level the C.A-'I.2 produces 0.1 dl_ less than the 110 dB rating, As
an exnrtlple, thecalibrator will only emit 109.7 dB at the city of Den-
ver (6000 feet elevation}, Therefore, a soaad level meter should be
set nt 109,7 dB, not at the rated 110 dlL
25
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