Conductive devices for monitoring liquid level and opening and closing switch contacts at predetermined liquid level thresholds.
A conductive 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.
- External Mounted Tank Level Sensors
- Waste Water Level Sensors
- Water Level Transmitters with 4-20mA Output
- ATEX Approved Liquid Level Sensors for Hazardous Areas
Conductive liquid level switches are threshold contact trip devices which typically consist of one or two metal rods extending out from the switch probe housing.
One of the metal rods has a custom length to reach the required liquid height.
The other metal rod extends down to a lower position, or alternatively the outer wall of a metal tank is used to complete the circuit.
When the liquid touches the custom length metal rod, the circuit is closed between the two electrodes.
Both electrodes are wired to an electrode controller module which maybe fitted within the probe housing or connected remotely. The controller will monitor the two electrodes and when the resistance changes, due to the liquid touching both electrodes, it will activate the switch contacts.
Additional liquid level switching thresholds can be achieved by incorporating more metal rods into the switch assembly, each one providing an additional level switching channel.
- Measuring 125 mm of water level range to 1mm accuracy
- 1.6 mH2O submersible transmitter for wash water break tanks
- Battery powered, 10m range, diesel oil tank level gauge with submersible probe
- Water tank level gauge transmitter with adjustable range
A conductive 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.
Unlike capacitive type liquid level sensing probes, the conductive type works best with conductive liquid media.
Since the conductive 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.
In comparison to other liquid level switch technology the conductive type is much easier to produce, and is often a much more economic option.
Conductive liquid level sensing probes are generally mounted through the top of a tank with the probe protruding into the tank.
- 1 metre depth range Titanium housing submersible transducer
- Generator diesel tank height level sensor for 1 metre height
- IP68 sewage level transmitter for monitoring up to 6 metres depth of waste water
- Aquaculture submersible freshwater level & temperature transmitter
Advantages
- Inexpensive product design, lowest cost type of liquid level switch
- Multiple switch points can be incorporated into one device
- No moving parts requiring regular inspection and maintenance, or leading to wear and tear
- Simple mechanical construction
- Works well with conductive media
- High temperature fluid compatibility, since there are no sensitive components making contact with the fluid
- Sealed pressurised or evacuated vessels will not affect performance
- SG & density insensitive
Disadvantages
- Some types may produce sparks when probe is in proximity to fluid
- Deterioration of probe tips due to residue, electrolytic effect or chemical corrosion leading to pitting, plating, or fouling
- Thick or sticky media will leave a coating on the probe creating an insulation layer causing malfunction
- Requires a higher voltage level across probes when used with less conductive liquids
- Probe protruding into liquid causing obstruction, attracting fouling and hygienic cleanliness issues
- 40 foot high diesel tank submersible pressure sensor
- Hazardous Area Submersible Hydrostatic Liquid Level Sensors
- CIP protected dairy sensor for measuring level of milk in 6m high tank
- Water depth and temperature transmitter for 700 foot deep borehole
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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
- 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