Presented By:
Jitendra Soni

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Liquid Level Measurement Based on Ultrasonic Echo Characteristic
introduction
 Ultrasound is high frequency mechanical vibrations or pressure waves
 Uses sound waves(>20000Hz)
 Sound waves are transmitted as a series of compressions and rarefactions
 Wave propagation is longitudnal and mechanical displacement in same direction
About Ultra Sonic Technique
 Ultrasonic level sensors are used for non-contact level sensing of highly viscous liquids, as well as bulk solids
 The sensors emit high frequency (20 kHz to 200 kHz) acoustic waves that are reflected back to and detected by the emitting transducer.
 The requirement for electronic signal processing circuitry can be used to make the ultrasonic sensor an intelligent device
Types of level measurement
 Non-Contact direct level sensor
 Level is a function of the time it takes an ultrasonic pulse to hit the surface and return
 Principles of Ultrasonic Inspection
 Ultrasonic waves travel in a straight line and at a constant speed until they encounter a surface.
 some of the wave energy is reflected and some is transmitted.
 The amount of reflected or transmitted energy can be detected and provides information about the size of the reflector.
 The travel time of the sound can be measured and this provides information on the distance that the sound has traveled.
ultrasonic instrument
 Attenuation mode
 A transmitter sends ultrasound through one surface
 Receiver detects the amount reaching it on another surface
 Imperfections reduce the amount of sound received
 Efficiency is increased by couplant usage
 Test Techniques
Divided into three primary classifications:
 Pulse-echo and Through Transmission
 Normal Beam and Angle Beam
 Contact and Immersion
 Contact Transducers
Level measurement sensors
 FLOAT SWITCHES
 NON CONTACT/CONTACT ULTASONIC SENSORS
 CAPACITANCE LEVEL SENSORS
 NUCLEAR LEVEL SENSOR
ACOUSTIC IMPEDANCE
 It is a frequency depended parameter
 Mathematically
Z=p/v*s
where, p=sound pressure
s=surface area
v=surface velocity
results are recorded in the form of curves
Advantage of Ultrasonic Testing
 Sensitive to small discontinuities
 Depth of penetration for flaw detection
 Single-sided access is needed
 High accuracy
 Electronic equipment provides instantaneous results.
 Detailed images can be produced with automated systems.
Limitations of Ultrasonic Testing
 Surface must be accessible.
 Skill and training is required
 Normally requires a coupling medium
 Cast iron and other coarse grained materials are difficult to inspect due to low sound transmission and high signal noise.