GE 37 400, Technical Reference And Operating Manual

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5 Operation Making measurements
5-36 Issue 2 (12/2013) USM 36
5.9 Making measurements
General notes
Please pay attention to the following notes when using
the USM 36 for measurements:
● To ensure proper measurements, please make sure
to calibrate correctly.
● All amplitude measurements are made at the highest
or the first signal in the gate.
● All distance measurements are made at the intersec-
tion point between the gate and the first echo flank
( TOF MODE = FLANK , J-FLANK , FIRST PEAK ) or
at the peak of the highest echo in the gate ( TOF
MODE = PEAK ).
● If the amplitudes of the echoes in the gate do not ex-
ceed 5 % screen height, all corresponding sound
path and amplitude readings are rejected. This en-
ables to avoid quickly changing, random readings
based on background noise of the USM 36.
The following example shows the dependency of dis-
tance measurement on the echo waveform, i.e. on the
height of the gate threshold and thus on the selection of
the intersection point at the signal.
Gate A set to 20 % screen height
measured sound path SA/ = 78.46 mm
Gate B set to 80 % screen height
measured sound path SB/ = 78.87 mm