Environmental, electrostatic and radio frequency criteria for all channels
Effect of humidity < 0.5 dB (for 30%<RH<90% at 40C and 1000 Hz)
Effect of magnetic field < 15 dB (A) or < 25 dB (Z) (for 80 A/m and 50 Hz)
Effect of radio frequency fields < +/-0.5 dB @ 74 dB and 10V/m
electromagnetic field
The greatest susceptibility (the least immunity) is achieved when the SLM is placed parallel to the radio
frequency field and the Z filter and time weighting Fast are selected and the SPL measurements are
considered.
The instrument produces greatest radio-frequency emission when an extension cable is connected. The cable
placed as a solenoid may produce unexpected emission depending on its physical dimensions. Any
configuration w/o extension cable reduces emission below 30 dBuV/m.
Effect of electrostatic discharge meets requirements of IEC 61672-1:2013
During electrostatic discharge, the influence of the displayed results could be observed.
No changes in instrument operation state, configuration or stored data corruption were found out.
Effect of ambient pressure < 0.01 dB/kPa
Effect of temperature < 0.5 dB (from -10C to + 50C)
Operating temperature from -10C to + 50C
Storage temperature from -20C to + 60C
Effect of Vibration < 71 dB (from 20 Hz to 1000 Hz at 1 m/s
2
) – see Chapter C.1.4
Calibration
Acoustical - with the SV 36 sound calibrator (or equivalent):
114.0 dB (equal to the calibrator pressure level - see
calibration chart of the used calibrator)
• Calibration level for the free field and
0 deg incidence angle
114.04 dB (equal to the calibration level for the pressure
field minus free field correction of MK 255 at 1000 Hz – see
Table C.1.6)
Note: The above levels correspond to 114 dB of calibrator’s sound pressure. If the calibrator
has a different sound pressure than 114 dB, the calibration levels must be accordingly
adjusted.
Microphone
MK 255 prepolarised free-field ½” condenser microphone
Nominal sensitivity 50 mV/Pa (corresponding to -26 dBV/Pa re 1 V/Pa)
Capacitance 17 pF
Reference point geometric centre of the microphone diaphragm.
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