Download Manual - Delta Ohm S.r.l.

Modern sound level meters, like HD2110L, apply corrections that can modify microphone
responses according to the acoustic field in which they are used. In this way you can, for example,
make measurements in indoor environments, in presence of multiple sound sources and anyway in a
reverberant field, with a microphone optimized for free field, by activating the correction specific
for random incidence. Applying this adjustment, the free field microphone will give a response
similar to that of a diffuse field microphone.
ENVIRONMENTAL INFLUENCE
Temperature
Sound level meters are designed to work at temperatures included in the range: -10°C ÷
+50°C. Most accurate sound level meters, like HD2110L, can have adjustment circuits for thermal
drifts aiming to reduce at minimum the measuring error over the whole temperature range. It is suggested, however, to avoid sudden variations that might cause condensation. Furthermore, be sure
that the instrument is in thermal equilibrium before carrying out a measurement or a calibration
(just wait an hour after temperature has changed.
Humidity
The HD2110L sound level meter and the microphone are not affected by relative humidity
up to 90%. However, protect the microphone from rain and snow and keep it clean. In case of bad
weather, it is suggested to use a windshield and, in case of use in very humid environments, the
proper microphone dehumidifier should be applied.
Pressure
Microphone sensitivity depends on atmospheric pressure. Sensitivity increases as pressure
decreases and the change of sensitivity measured at 250 Hz is always lower than ±0.03dB/kPa in
the range 85kPa ÷ 108kPa as required by IEC 61672 for class 1 sound level meters. Sensitivity drift
with ambient pressure is usually worse at high frequencies, even if the sensitivity maximum difference in the range 85kPa ÷ 108kPa remains within ±0.5dB over the whole sound spectrum.
Wind
To reduce wind disturbance as much as possible, it is suggested to use the proper windshield, consisting of a polyurethane porous globe to be placed on the microphone.
This useful accessory protects also from dust, dirt, rain and snow. The presence of a windshield
slightly alters the microphone frequency response and more accurate sound level meters are provided with a correction curve to compensate this effect.
Vibrations
Even though microphone and sound level meter cannot be easily affected by vibrations, it is
better to isolate both instrument and microphone from strong vibrations.
Magnetic Fields
The influence of electrostatic and magnetic fields on the sound level meter is negligible.
PRECAUTIONS AND GENERAL HINTS OF USE
• Ensure that ambient conditions fit the use of a sound level meter. Take care that the instrument
has reached thermal equilibrium, that there is no condensation on metal walls and that temperature, relative humidity and pressure are within the limits specified by the manufacturer. The use
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