Cirrus Optimus+, Instrument Handbook

Page: 46 / 53

Page 46
Sound Level Meters – User Manual
9.3.1 Battery type
The battery should be an alkaline battery, not an ordinary dry cell. The battery is 9 volts when
new and will operate the calibrator down to 6.4 volts.
When the battery voltage is below 6.6 volts but above 6.4 volts, the power LED will flash to
indicate that the battery voltage is low. When the battery voltage is below 6.4 volts, the
calibrator will not switch on.
A discharged battery may allow switch-on but will soon drop in voltage and indicate low battery
or switch off.
9.4 Specifications
Frequency
1 kHz ± 1%
Sound level 94 dB re 20 µPa
Standardisation CR:514 - IEC 60942:2003 Class 2
CR:515 - IEC 60942:2003 Class 1
Distortion Less than 2%
Operating humidity 25 to 90% relative humidity
Operating static pressure 65 kPa to 108 kPa
Operating temperature -10
°
C to +50
°
C
Storing temperature -20
°
C to +60
°
C
Effective volume 6.19 ± 0.2 cm3
Cavity diameter 0.525 inch
Battery 1 x 9 V 6F22 (NEDA 1604)
Battery life Approx. 15 Hours Continuous Use
Battery voltage 9 V Nominal (10 V max, 6.4 V min)
Weight with battery 185 g
Dimensions 135 mm x Ø 48 mm
9.5 Technical information
9.5.1 Free Field Correction
When calibrating a microphone that is to be used for free field measurements, a small correction
may be necessary to compensate for the difference between the microphone’s free field
response at ‘zero degrees’ or ‘head-on’ incidence, and the pressure level generated by the
calibrator.
The correction is typically -0.3 dB for Cirrus ½ inch microphones (making the effective calibration
level 93.7dB).