Ultrasonic devices for monitoring liquid level and activating the opening and closing of switch contacts at predetermined liquid level thresholds.
A ultrasonic liquid level switch is an instrument for monitoring the height of a liquid and tripping a relay contact switch or transmitting a solid state relay switch output when a maximum, minimum or intermediate level has been reached. The liquid level switch output can then be utilised by other instrumentation to open a valve, illuminate a warning lamp, activate an audible alarm, or switch on a pump.
Featured liquid level measurement products
0-10 Volts Output Hydrostatic Sensors, Probes & Transducers - Choose 0-10V output hydrostatic sensors, probes & transducers for accurate liquid level and head pressure measurement. Ideal for industrial tanks, boreholes & process control systems.- Hydrostatic Level Sensors - Hydrostatic pressure sensing devices for measuring liquid level and converting it to an electrical signal to send to other instrumentation.
Ultrasonic liquid level switches are contactless measurement devices which transmit and receive high frequency acoustic waves to measure the distance to the surface of a liquid based substance.
Ultrasound liquid level switch technology transmits a high frequency sound wave pulse and receives the wave echo reflected off a liquid surface. The time taken for the acoustic pulse to traverse the distance between the transmitter and target surface, and back again to the receiver is measured.
The distance (d) between the ultrasonic liquid level switch and the liquid surface can be calculated by dividing the time taken (t) by two, and multiplying that by the speed of sound (c) in air, i.e. d = c ∙ t / 2. The liquid level in a tank (LT) can then be determined by subtracting distance (d) from the height of the ultrasonic level switch (HT), i.e. LT = HT – d.
The performance of a ultrasonic level switch is mainly affected by changes in the speed of sound and disturbances on or above the surface of the liquid.
The speed of sound will change if the air density changes. Since air density changes in the Earth’s atmosphere are directly related to changes in air temperature (measured in Kelvins), an ultrasonic fluid level switch is compensated by incorporating an air temperature sensor.
Featured liquid level measurement products
HART flameproof (Ex d) re-scalable level transmitter for hydrostatic head up to 2 metres - HART compatible, ATEX flameproof approved, rangeable level transmitter to measure hydrostatic head of water/glycol or mineral oil fluid within a reservoir about 2 metres in height.
Generator diesel tank height level sensor for 1 metre height - Prevent generator downtime and fuel theft with this easy-to-install diesel level sensor. 0.5 to 4.5Vdc output for seamless integration with MCUs.
Surface effects can be reduced by experimenting with the position of the device, installing within a stilling well or wave guide, and some ultrasonic devices include features to minimise the effects of foaming, bubbles, vapour and turbulence.
Since there is no contact with the fluid to be measured, ultrasound liquid level measurement technology can be used in applications where switches requiring contact are otherwise prohibited.
Ultrasonic liquid level switches are typically housed in a single assembly combining the acoustic transmitter and receiver in one device.
Since ultrasonic liquid level switches do not make contact with the liquid media to be measured, they are mounted above the surface of the liquid in the top of a tank or from a platform spanning the top of an open tank.
Featured liquid level measurement products
- LMK331 Screw-In Ceramic Level Transmitter - Level pressure sensor with semi-flush ceramic diaphragm and stainless steel or PVDF wetted parts in ranges from 0-4 to 600mH2O gauge.
Hydrostatic Liquid Level Voltage Output Pressure Transducers - Precision liquid level measurement with amplified voltage output hydrostatic pressure transducers. Ideal for industrial tanks, pump control, and volume calculation. 0-10V, 0-5V, and more.
Advantages
- No media contact for vertically mounted type, so flexibility for use on different corrosive media, thick fluids, slurries, wastewater
- High temperature fluid compatibility for vertically mounted types, since no sensitive components make contact with the fluid
- High accuracy due to high frequency pulse wave and precise transit time time measurement
- Multiple switch contacts in one device
- Operates with conductive or non-conductive fluids
- Sealed pressurised vessel will not affect performance
Disadvantages
- Foaming, splashing, vapour and humidity can affect measurement performance
- High cost compared to other technologies
- Top mounting only unless using point level type
- Minimal blocking distance limited operation when in proximity to liquid level
- Temperature compensation required to compensate for speed of sound variation with air temperature
- Sound waves cannot be transmitted through a vacuum
Featured liquid level measurement products
Water Level Transmitters with 4-20mA Output - Browse for 4-20mA water level transmitters using two-wire loop power. Ideal for wells, tanks, rivers & reservoirs with excellent noise immunity & long cable runs.
Low power consumption SDI-12 lake water level sensor - Monitor lake water levels accurately with this low power SDI-12 sensor. Features durable PUR cable and PC logging software for easy data analysis.
Related Help Guides
- Determining the hydrostatic pressure range for a tank level sensor
- Measuring liquid level in a sealed tank with a hydrostatic pressure sensor
- Difference between vented and non-vented water level measurement
- Determining water tank volume using hydrostatic pressure
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- Installing a submersible level sensor horizontally
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- Using absolute pressure sensors to measure hydrostatic level
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- Considerations for monitoring Landfill Water Level
- Why are Submersible applications so demanding of Pressure Transducers?
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- Converting non-vented depth readings & barometric pressure to true depth
Related Technical Terms
- Capacitive Fluid Level Measurement
- cmH2O – Centimetres of Water Column at 4 deg C Pressure Unit
- Conductive Fluid Level Detection
- Float Fluid Level Detection
- ftH2O – Feet of Water Column at 4 deg C Pressure Unit
- mH2O – Metres of Water Gauge at 4 deg C Pressure Unit
- mmH2O – Millimetres of Water Column at 4 deg C Pressure Unit
- Specific Gravity
- Vibrating Tuning Fork Fluid Level Detection
Related Online Tools
- Liquid Level to Hydrostatic Pressure Calculator
- Fluid Depth, Density, Gravity, and Pressure Calculator
- Liquid Level Transmitter 4-20mA Current Output Calculator
- Vertical Cylindrical Shaped Tank Contents Calculator
- Horizontal Cylindrical Shaped Tank Contents Calculator
- Rectangular Shaped Tank Contents Calculator
- Pressure to Liquid Level Calculator
Related Product and Application Guides
Related Application Questions and Answers
- HART flameproof (Ex d) re-scalable level transmitter for hydrostatic head up to 2 metres
- Dockside sea water tide level transmitter up to 6 metres depth
- Water tank level gauge transmitter with adjustable range
- Portable battery powered tank level gauge with submersible sensor
- Generator diesel tank height level sensor for 1 metre height
Contact us about this Ultrasonic Liquid Level Switches page to request more information, or to discuss your application requirements.