Measurement and point detection devices for monitoring liquid level and activating switch contacts at predetermined liquid level thresholds.
A 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 an warning lamp, activate an audible alarm, or switch on/off a pump.
Featured liquid level measurement products
Hydrostatic Level Sensors - Hydrostatic pressure sensing devices for measuring liquid level and converting it to an electrical signal to send to other instrumentation.
LMP307 Submersible Level Transmitter - Submersible level transmitter for measuring liquid level with a 4-20mA current loop or a 0-10V voltage output plus optional ATEX approval for intrinsically safe use in hazardous areas in ranges from 1mH2O up to 250mH2O. The LMP307 is suitable for use on potable water with no leaching, and can be supplied with a drinking water certificate according to DVGW and KTW.
There are two basic types of liquid level switches, those that detect the presence of liquid known as point level detection, and those that are continuously monitoring the variation in level to detect when a threshold has been reached.
Point level switches have to be mounted so that the sensing probe makes contact with the fluid. They are simpler to set-up and calibrate, since the installation position dictates the switch point, however this also limits where the point level sensor can be installed.
There are many applications on a liquid storage tank where a switch provides a lower cost and simpler installation for managing tank contents because there is no need for additional signal conditioning instrumentation, and some switch types are mechanically activated and require no electrical supply or electronic circuits to function.
Featured liquid level measurement products
Hydrostatic Liquid Level Switches - Select hydrostatic level switches for precise threshold detection in tanks. Understand density effects, sealed tank solutions, and flush diaphragm benefits.
S12S SDI-12 Coms IP68 Pressure and Temperature Sensor - Combined pressure and temperature sensor with a 1200 baud rate serial data interface as defined by the SDI-12 support group.
Product Type Comparison Table
Please use the table below to compare the advantages and disadvantages of each liquid level switch technology type versus application and specification parameters.
| float | conductivity | capacitive | hydrostatic | tuning fork | ultrasonic | |
|---|---|---|---|---|---|---|
| media contact | yes | yes | yes | yes | yes | no |
| moving parts | yes | no | no | yes | yes | no |
| surface disturbance sensitive |
no | no | no | no | no | yes |
| pressurised vessel | yes, low pressures | yes | yes | more difficult | yes | yes |
| vacuum evacuated vessel | yes | yes | yes | more difficult | yes | no |
| installation position | top, side, bottom | top, side, bottom | top | side, bottom | top, side, bottom | top, side |
| thick fluids | no | no | no | yes with flush diaphragm | no | yes |
| protrusion into tank | yes | yes | yes | no | yes | no |
| sg density variation sensitive | no | no | yes | yes | yes | no |
| fouling degrades performance | yes | yes | yes | yes | yes | no |
| multiple point level detection | vertical entry yes, side entry no | vertical entry yes, side entry no | yes | yes | vertical entry yes, side entry no | top entry yes, side entry no |
| accuracy | low | low | low | high | high | high |
| cost | low | low | high | high | high | high |
| power supply required | no | yes | yes | yes | yes | yes |
Featured liquid level measurement products
River level sensor for run-of-the-river hydropower monitoring up to 4m - Vented pressure river level sensor for measuring water level up to 0.4 bar in run-of-the-river hydroelectricity systems.
Waste Water Level Sensors - Find wastewater level sensors with open face flush diaphragms designed for sewage and effluent. Learn about clog resistance, intrinsic safety, and material selection for reliable hydrostatic level measurement.
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
- Measuring the volume of liquid in a horizontal cylinder tank
- Measuring liquid level in a tank using a dp sensor
- How do you measure the volume of a liquid using pressure
- Liquid Level Measurement
- How to determine milk tank level and volume from pressure
- Selecting the correct pressure sensor range for low-level applications
- Installing a submersible level sensor horizontally
- Measuring diesel level in shallow tanks
- Atmospheric pressure compensation for hydrostatic level sensors
- Determining the signal cable length of a suspended liquid level transducer
- Calculating required pressure range for fuel tank level measurement
- How does changes in Local Gravity affect Hydrostatic Pressure
- Using absolute pressure sensors to measure hydrostatic level
- Using a screw-in or waterproof pressure transmitter to measure liquid level
- Improve the electrical termination of vented submersible pressure sensors
- Considerations for monitoring Landfill Water Level
- Why are Submersible applications so demanding of Pressure Transducers?
- Are all IP68 Water Resistant Protection Ratings the same
- 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
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Contact us about this Liquid Level Switches page to request more information, or to discuss your application requirements.