Capacitive Liquid Level Switches

Capacitive switches for opening or closing electrical contacts at a preset liquid level thresholds.

A capacitive liquid level switch is an instrument for monitoring the height of a liquid and tripping a relay contact switch or transmitting 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

External Mounted Tank Level Sensors - External mounted level sensors for installing on the outside of a liquid storage tank to measure level of tank contents.
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.

Capacitive liquid level switches are threshold contact trip devices which typically consist of a single probe which acts as an immersed electrode inside a tank. This probe interacts with an opposite electrode, usually the the wall of the tank or an outer tube, and the two are connected together to form a capacitor.

The liquid contents of the tank act as the dielectric medium, which will affect the capacitance created between the two electrodes. If the liquid level rises and falls, this will change the capacitance measured by the probe in a predictable way, and therefore it can be used very effectively as a measurement of liquid level.

Featured liquid level measurement products

Storm surge protected low range submersible river level transmitter - This submersible level transmitter offers accurate low range water level monitoring with high overpressure resistance for storm surge protection in rivers
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.

A capacitive liquid level switch probe makes direct contact with the liquid to be measured, and therefore material compatibility has to be a consideration, but for most applications a stainless construction is more than adequate for most fluids.

Since the capacitive level switch probe is essentially a stainless steel rod fitted to a tank, it is possible to construct the device to withstand high pressures so that it can be used on sealed pressurised tanks.

Also, since there is no sensitive components immersed in the fluid it is possible to use them on higher temperature media that would not be tolerated by other types of liquid level switch.

Capacitive liquid level sensing probes are generally mounted through the top or side of a tank with probe protruding into the tank. Probes mounted into the side of the tank will activate when the fluid reaches the probe. Probes that extend down the tank can be set to trigger at different levels using multiple contact switch relays.

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.
DS200 Combined Hydrostatic Level Switch, Gauge and Sensor - Three in one hydrostatic level switch, digital level gauge and level sensor with level ranges from 1 mWG up to 600 mWG (3.3 to 1969 ftWG).

Advantages

Works well on dielectric fluids
Simple mechanical construction
No moving parts requiring regular inspection and maintenance, or leading to wear and tear
High temperature fluid compatibility since no sensitive components make contact with the fluid
Sealed pressurised or evacuated vessels will not affect performance

Disadvantages

Doesn’t work with conductive fluids without insulated outer tube
Thick or sticky media will leave a coating on the probe creating an insulation layer causing malfunction, or affect performance
Requires calibration to distinguish difference between liquid and air.
Sensitive to changes in media which cause dielectric constant to change
Probe protruding into liquid causing obstruction, attracting fouling and hygienic cleanliness issues

Featured liquid level measurement products

IMCL Low Cost Submersible Pressure Sensor - Economical IP68 protected sensor with stainless steel 316L housing and Ceramic strain gauge sensing diaphragm for measuring liquid depth pressure.
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.