Casella CEL CEL-393 - Manual (Page 82)

This will ensure that all of the requirements of the international standards
are still met. For some specialised applications specific approvals are
required and details are available on request.
Traceability to UK national standards can be provided by our NAMAS
accredited calibration laboratory by the issue of a formal certificate of
calibration. Please ask for details of this service.
The CEL-393 A and B versions are also type approved for official
calibration by the PTB in West Germany, under the reference number
shown in Figure 10, and may be submitted to the calibration laboratories
complete with an R05001 pistonphone and optional extension cable and
windshield. A special approvals label is required and further information
is available on request. The verified measurement ranges under this
approval are shown in Figure 11.
Further approvals have been granted in both Switzerland and Austria.
8.2 CEL-284/2 Electro Acoustic Calibrator
In line with accepted instrument practice, the instrument should be
calibrated before and after each major measurement sequence. The
CEL-284/2 Precision Acoustic Calibrator should be used for calibrating
the A and B versions, while the procedure described for pistonphones
should be used for the C and D versions.
Having checked the batteries in both the meter and calibrator, the
procedure to be followed for A and B versions is as follows. Place the
microphone into the calibration cavity (following the instructions provided
with the calibrator) ensuring that it is correctly seated on the shoulder in
the cavity.
Both calibrator and sound level meter should be switched ON, and the
latter set to the 70dB range (7R), A-weighted response, and fast (F) time
constant with the SPL mode. The instrument takes approximately 90
seconds to reach its nominal operating conditions, after which time it
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