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.
LMK458 Marine Approved Hydrostatic Level Transmitter
LMP305 Borehole Level Transmitter
DPT200 Pressurised Tank Level Differential Pressure Transmitter
External Mounted Tank Level Sensors
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.
3 metre range submersible freshwater level transmitter
Dockside sea water tide level transmitter up to 6 metres depth
LMK457 Marine Approved Level Transmitter
SLS-D SDI-12 Digital Interface Submersible Level Sensor
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 |
Fresh water compatible submersible 1mH2O range 4-20mA output pressure sensor- 50m seawater depth and temperature sensor with SDI-12
- DPT200 Pressurised Tank Level Differential Pressure Transmitter
Dual input indicator to display & calculate the liquid level of a pressurised tank
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Related Definitions
- 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 Tools
- Fluid Depth, Density, Gravity, and Pressure Calculator
- Vertical Cylindrical Shaped Tank Contents Calculator
- Horizontal Cylindrical Shaped Tank Contents Calculator
- Rectangular Shaped Tank Contents Calculator
- Pressure to Liquid Level Calculator
- Liquid Depth/Level to Hydrostatic Pressure Calculator
- Liquid Level Transmitter 4-20mA Current Output Calculator