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.
- 0-10 Volts Output Hydrostatic Sensors, Probes & Transducers
- Water Level Transmitters with 4-20mA Output
- Waste Water Level Sensors
- 4-20mA Output Hydrostatic Level Transmitters & Sensors
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.
- 50 metre borehole water depth transmitter for dry running protection
- Genset hydrostatic sensor for measuring level of small diesel tank up to 12 inches
- 300 cm water level sensor for submersing in tank
- 10 metre / 32.8 feet deep fresh water level and temperature digital sensor
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.
- Low power consumption SDI-12 lake water level sensor
- HART flameproof (Ex d) re-scalable level transmitter for hydrostatic head up to 2 metres
- 40 foot high diesel tank submersible pressure sensor
- 2 mWC waste water submersible pressure transmitter with 1/2 BSP female fitting
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
- Protecting low range river level sensor from storm surges
- Hydrostatic Liquid Level Voltage Output Pressure Transducers
- Cement plant process water basin level sensor
- High temperature water level transmitter for measuring up to 1 mWG
Related Help Guides
- Measuring liquid level in a tank using a dp sensor
- Measuring liquid level in a sealed tank with a hydrostatic pressure sensor
- Using a screw-in or waterproof pressure transmitter to measure liquid level
- How to determine milk tank level and volume from pressure
- Measuring the volume of liquid in a horizontal cylinder tank
- How do you measure the volume of a liquid using pressure
- Improve the electrical termination of vented submersible pressure sensors
- Difference between vented and non-vented water level measurement
- Determining water tank volume using hydrostatic pressure
- Calculating required pressure range for fuel tank level measurement
- Using absolute pressure sensors to measure hydrostatic level
- Determining the hydrostatic pressure range for a tank level sensor
- How does changes in Local Gravity affect Hydrostatic Pressure
- Considerations for monitoring Landfill Water Level
- Why are Submersible applications so demanding of Pressure Transducers?
- Determining the Signal Cable Length of a Suspended Liquid Level Transducer
- Are all IP68 Water Resistant Protection Ratings the same
- Converting non-vented depth readings & barometric pressure to true depth
- Liquid Level Measurement
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
- Fluid Depth, Density, Gravity, and Pressure Calculator
- Liquid Level to Hydrostatic 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