Casella CEL CEL-414 - Manual (Page 22)

Type 2 Microphone
1. Ensure the power is OFF, i.e. the
screen is blank.
2. Insert the CEL-230 Microphone/Pre-
amplifier Unit into the socket at the
top of the instrument.
3. Locate the unit in the keyway to ensure
the pins are engaged before pushing
it into place.
DO NOT USE PLIERS OR OTHER
TOOLS.
All Microphones
To avoid reflections from the Operator’s
body, it is suggested that the micro-
phone be positioned remote from the in-
strument. This is best achieved by
mounting the microphone and preampli-
fier on a CEL-4627 Tripod. The assembly
is then connected to the instrument by
plugging it in to one end of a CEL-
4493/10 Extension Cable, the other end
of which is plugged into the preamplifier
socket on the sound level meter body.
It is recommended thatType1 instru-
ments be used with the CEL-2962 Wind-
shield and Type 2 with CEL-4672/2
Windshield that fit over the microphone
In addition to preventing errors induced
by wind noise, windshields inhibit the
build up of dust and dirt on the dia-
phragm which can influence the calibra-
tion. A windshield will also protect the
diaphragm from being punctured by any
fast moving particles that may be thrown
up by passing vehicles when measuring
traffic noise, exhaust systems, or other
high speed industrial processes.
The Windshield should be removed and
washed from time to time in clean water
with a little detergent. Ensure that it is
thoroughly rinsed and dried before refit-
ting.
If the sound level meter is to be used
with an external filter set, they should be
connected together now. Refer to the
relevant filter set hand book to see how
this should be done.
The sound level meter is now ready for
service.
In accordance with accepted measure-
ment practice, it is recommended that a
field accuracy check (acoustic calibration)
is performed before and after each series
of readings. Calibration procedures are de-
tailed in Chapter 5.
The field accuracy check procedure (often
referred to as acoustic calibration) should
be performed in the field immediately be-
fore and after measurements are made.
When making such a check, the maxi-
mum noise level in the area must be at
least 20 dB below the generated calibra-
tion level.
It is recommended that acoustic calibra-
tion of Type 1 instruments be performed
with a CEL-284/2 Acoustic Calibrator (IEC
942 Class 1L), with a CEL-282 (IEC 942
Class 2L) used for Type 2 instruments.
(When no Class 1 calibrator is available, a
Class 2 calibrator may be used with Type
1 instruments.)
Proceed as follows.
5. FIELD ACCURACY CHECK (ACOUSTIC CALIBRATION)
Page 18 - General CEL Sound Level Meters Handbook