This type of level switch uses ultrasonic sound
waves to detect the presence of process material either solid or liquid at one
point.
The Working Principle
Sound waves pass back and forth within the gap of
the probe, sent and received by piezoelectric transducers. The presence of any
substance other than gas within the gap detects the received audio power, thus
signalling to the electronic circuit within the bulkier portion of the device
that process level has reached the detection point.
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| Fig 1 |
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| Fig 2 |
In Fig 1, the sound passes through the gap when filled with liquid (wet gap).
In Fig 2, the sound cannot pass through an
air-filled gap (dry gap).
The lack of moving parts makes this probe quite
reliable although it may be become fooled by heavy fouling.
You can also read: The Working Principle of Ultrasonic Flow Meters
Some of the industrial applications of Ultrasonic level switches include:
- Leak detection
- As an overfill alarm
- Detection of presence of liquids in pipeline
- Pump Protection
- Engine oil level control
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