·Vibration Measurements
The instrument can be calibrated
at
1 g peak
80Hz
using Accelerometer
Calibrator
Type 4291.
Sound, Vibration, and Voltage Measurements
A reference voltage
is
incorporated
to
check
the
amplifiers and meter
circuit.
Stability
is
better than ± 0.2
dB
over the range of operating tempera-
tures.
8.13. DIRECTIONAL CHARACTERISTICS
See chapter "Operational Characteristics and Accuracy", section 5.1.
8.14. EFFECT
OF
VIBRATION
See Fig.5.14.
8.15. EFFECT
OF
SOUND
FIELD
ON
AMPLIFIERS
At least
60
dB
below sensitivity
of
one inch microphone. See Fig.5.13.
8.16. EFFECT
OF
STATIC PRESSURE
Approx.
-0.003
dB
per
mm
Hg.
See section 5.6.
8.17. EFFECT
OF
MAGNETIC FIELD
With one inch microphone fitted, a magnetic field due
to
a current
of
80
Ampere turns/metre (approx. 1 Oersted) produces a meter deflection
of
36
dB
SPL.
8.18. EFFECT
OF
HUMIDITY
Less than 0.5
dB
for relative humidity 0
to
90%.
112
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