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
18.605 G Low Cost Submersible Diesel Fuel and Water Tank Level Sensor - Low cost OEM diesel fuel or water level sensor for installing inside or outside a storage tank. 
LMK809 Plastic Submersible Low Level Transmitter - IP68 low range pressure transmitter for measuring the level of highly contaminated and agressive liquid media with a body made from PP-HT or PVDF.
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
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.
LMP307T Submersible Level and Temperature Transmitter - The LMP307T is a submersible level and temperature transmitter with a level sensing range from 1 to 250 mH2O and a temperature sensing range of 0 to 30°C up to 70°C.
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
Submersible water level and temperature probe with SDI-12/USB interface for freshwater monitoring - Versatile 10m water level and temperature probe with USB and SDI-12 connectivity, designed for hydrological studies and long-term environmental monitoring programs.
CIP protected dairy sensor for measuring level of milk in 6m high tank - Hygienic pressure sensor designed for CIP cleaning in dairy applications. Withstands harsh chemicals and high temperatures. Accurate and reliable level measurement in milk silos.
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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
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- Vertical Cylindrical Shaped Tank Contents Calculator
- Horizontal Cylindrical Shaped Tank Contents Calculator
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