Liquid level sensors are used to detect liquid levels
or interfaces between liquids such as oil and water or liquids and
solids. They can be defined as sensors or transducers, or as integrated
systems with instrumentation and control capabilities.
Types of Sensors
Liquid level sensors provide measurement of the
height or position of a fluid surface using a variety of different
technologies and methods.
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Air bubbler systems involve a fixed flow of air passed through a tube with an opening below the surface level of the measured liquid. Pressure is proportional to the depth and density of the liquid.
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Capacitance sensors apply radio frequency signals to a capacitance circuit to sense materials with dielectric constants ranging from 1.1 to 88 or more.
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Conductivity or resistance sensors use a low-voltage power source applied across separate electrodes. Level is interpreted based on the amount of resistance or conductance of the substance which carries the current.
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Float sensors involve the opening or closing of a mechanical switch through either direct contact or magnetic operation from a device which floats on the surface of the measured liquid.
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Optical sensors detect the decrease or change in transmission of infrared light emitted from a diode through a material.
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Pressure membrane and differential sensors measure the pressure or change in pressure in a vessel such as a holding or storage tank.
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Radar or microwavesensors measure using the emittance and detection of microwave pulses.
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Ultrasonic or sonic liquid level sensors measure the length of time it takes for a reflected sound wave to return to a transducer from a target surface.
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Vibrating or tuning fork liquid level sensors use a piezoelectric crystal or other technology to vibrate a probe and then monitor the presence, absence, increase or decrease of that vibration.
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