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Technical Library |
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Liquid Flow Sensors |
Liquid flow sensors are used to measure volumetric or mass flow rates (such as litres
per second or kg/s). These measurements can be converted between one another if the materials
density is known. The density for a liquid is almost independent of the liquids conditions,
however this is not the case for a gas, whose density highly depends upon pressure, temperature
and to a lesser extent, the gas composition.
When gases or liquids are transferred for their energy content (such as the sale of Natural Gas)
the flow rate my also be expressed in terms of energy flow, such as GJ/hour or BTU/day. The
energy flow rate is the volume flow rate multiplied by the energy content per unit volume or
mass flow rate multiplied by the energy content per unit mass. Where accurate energy flow rate
is desired, most flow meters will be used to calculate the volume or mass flow rate which is
then adjusted to the energy flow rate by the use of a flow computer.
For liquids, other units are used depending upon the application and industry but might include
gallons (U.S. liquid or imperial) per minute, liters per second, bushels per minute and, when
describing river flows, cumecs (cubic metres per second) or acre-feet per day.
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Capacitance level sensors excel in sensing the presence of a wide variety of solids, aqueous
and organic liquids, and slurries. The technique is frequently referred to as RF for the radio
frequency signals applied to the capacitance circuit. The sensors can be designed to sense material
with dielectric constants as low as 1.1 (coke and fly ash) and as high as 88 (water) or more.
Sludges and slurries such as dehydrated cake and sewage slurry (dielectric constant approx. 50)
and liquid chemicals such as quicklime (dielectric constant approx. 90) can also be sensed.
Dual-probe capacitance level sensors can also be used to sense the interface between two immiscible
liquids with substantially different dielectric constants, providing a solid state alternative to
the aforementioned magnetic float switch for the “oil-water interface” application.
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Although we try to work with capacitance level sensors whenever possible, there
are many other types of liquid level sensors including vibrating point, rotating paddle,
magnetic and mechanical float, pneumatic, conductive, optical interface, ultrasonic,
microwave/radar, magnetostrictive, resistive chain, hydrostatic pressure, and air bubbler
measurement systems.
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Liquid Flow Sensor Information Links
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Liquid Flow Sensor Manufacturer Links
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