3
3.
Measuring principle
Level meter consists of an ultrasonic probe and an
electronic unit.Level meter is mounted on top of the container,
under the control of the electronic unit, the ultrasonic probe
transmitting ultrasonic pulses to the measured object.Sound
waves are reflected by the surface of the object, part of the
echo received by the probe and converted to electrical
signals.The meter measures the time between pulse
transmission and reception. The time is proportional to the
distance from the probe to the measured object. The
electronic unit detects this time and calculates the measured
distance based on the known sound velocity. Level value can
be obtained by the subtraction.
The speed of ultrasonic wave in the air is affected by the air
temperature, therefore, the Ambient temperature needs to be
detected when the level meter works, and the sound speed is
compensated to ensure the measurement accuracy
.Blind zone: Span F may not extend into the blind zone B.
Level echo from the blind zone cannot be evaluated due to the
transient characteristics of the sensor.
