CASELLA CEL CEL-450 Handbook page 65

Effect of Temperature:
Electrical accuracy of the instrument over -10 to
o
+50 C: < ±0.2 dB
Temperature coefficient of CEL-250 Microphone: 0.02
o
dB/ C.
Effect of Humidity:
Less than ±0.5 dB over the range 25 to 90% RH (non
condensing), relative to the reference conditions.
Supplied Microphone:
Class 1: CEL-250 ½" pre-polarised Free Field type for use with
CEL-495 Preamplifier,
Nominal sensitivity: 50 mV/Pa,
Capacitance: 18 pF.
Class 2: CEL-485 ¼" electret microphone incorporated into
preamplifier unit,.
No cable correction is required for microphone cables up to 10 m
(33 ft) when calibration is performed with C6716 or C6717
Cables fitted.
Calibration:
Direct for Class 1 CEL-250 Microphone used with CEL-495
Preamplifier.
Direct for Class 2 CEL-485 Microphone/Preamplifier Unit.
Manual, or automatic calibration to a user specified reference
level.
The date, time and offset of the last 4 calibrations are stored.
Power Supply:
Batteries: 4 x LR6 Alkaline cells.
Battery Life: Typically 15 hours in broadband mode, 12 hours
in narrowband mode.
Batteries may be safely left in the instrument whilst operating
from an external DC supply.
Specification
CEL-450/490 Operators Handbook - Page 65