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	Bubblers The operation of an air bubbler is similar to blowing air into a glass of water with a straw. The more water is in the glass, the harder one needs to blow. Bubbler-type level sensors have been in use for as long as compressed air has. If the air pressure entering the dip pipe is greater than the hydrostatic head of the process fluid in the tank, the air will bubble out at the bottom of the pipe.	0 Posts 0 Topics
	Capacitance and Radio Frequency (RF) Admittance Characteristic of probe-type sensors, the RF probes operate by applying a constant voltage to a metallic rod and monitoring the current that flows. This current is proportional to the admittance or capacitance	0 Posts 0 Topics
	Conductivity and Field-Effect Level Switches The ability of a liquid to conduct electricity is a function of the number of charged ions in that solution. Deionized pure water has very high resistance, but liquids such as sewage water, sea water, and city water are quite conductive	0 Posts 0 Topics
	Diaphragm Level Detectors All diaphragm detectors operate on the simple principle of detecting the force exerted by the process material against the diaphragm. The designs discussed below include diaphragm switches for liquid and solid services and diaphragm devices for continuous liquid level detection and transmission in tanks or wells	0 Posts 0 Topics
	Differential Pressure Level Detectors Liquid level can be measured (inferred) by measuring a differential pressure (d/p) caused by the weight of the fluid column in a vessel balanced against a reference	0 Posts 0 Topics
	Displacer Level Devices A level or a density instrument is sensitive to the apparent weight of an immersed displacer. If the cross-sectional area of the displacer and the density of the liquid are constant, then a unit change in level will result in a reproducible unit change in the apparent weight of the displacer	0 Posts 0 Topics
	Float Level Devices The immersion of a theoretically perfect float would have a perfectly constant immersion depth. The immersion of real floats is not perfectly constant because of the work they have to do to move the mechanical components of the instrument.	0 Posts 0 Topics
	Laser Level Sensors In recent years, laser-based level sensors have become accepted in industrial process control as a means of obtaining reliable noncontact level measurements in difficult applications. Process conditions or installation methods often preclude the use of more conventional noncontact gauges such as ultrasonic, radar, and nuclear devices, creating both a technical and economic advantage for laser technology.	0 Posts 0 Topics
	Level Gauges, Including Magnetic This section deals with liquid level gauges that operate by connecting a measuring chamber in parallel to the vessel being monitored so as to directly indicate the level visually or by the use of a magnetic indicator or transducer	0 Posts 0 Topics
	Microwave Level Switches This section discusses the use of side-mounted microwave level switches that are used in hard-to-handle solid, liquid–solids interface, and liquid–liquid interface applications	1 Posts 1 Topics	Last post by BobKat in liquid-solid interface d... on October 19, 2009, 06:59:00 PM
	Optical Level Devices The operation of optical level detectors can be based on the reflection, transmission, or refraction of conventional,laser, or IR light.	0 Posts 0 Topics
	Radar, Noncontacting Level Sensors Radar level transmitters and gauges use electromagnetic waves, typically in the microwave K- and X-bands ( ≈ 6 to 28 GHz), to make a continuous liquid level measurement. Most applications have been on liquid service, although several companies report small to moderate success on solids and powders.	0 Posts 0 Topics
	Radar, Contact Level Sensors (TDR, GWR, PDS) Modern contact radar level transmitters owe much of their existence to time domain reflectometry. Although new to the industrial level market, TDR technology has been used for decades. It has been employed for finding breaks in underground cables and the in-wall installations of large buildings.	0 Posts 0 Topics
	Radiation Level Sensors Radiation at different frequencies can be used for level measurement. Included are ultrasonic, radar (or microwave), laser (infrared light), neutron, and gamma forms of radiation. These different radiation forms are also of different strengths in terms of what materials they can penetrate	0 Posts 0 Topics
	Resistance Tapes Resistance tape for continuous liquid-level measurement was invented in the early 1960s, initially for water well gauging and subsequently for marine and industrial usage. The sensor is a flat, coilable strip (or tape) ranging from 3 to 100 ft (1 to 30 m) in length, suspended from the top of the tank. It is small enough in cross section to be held within a perforated pipe (2 to 3 in. diameter), which also supports the transducer and acts as a stilling pipe if the process is turbulent.	0 Posts 0 Topics
	Rotating Paddle Switches The main purpose of detecting the level of solids is to signal the breakdown in continuous solids flows, which usually occurs as a result of either arching or bridging (the blockage of flow due to the segregation and collection of larger-sized particles) or flushing and “ratholing” (the sudden dumping of large quantities as arches collapse)	0 Posts 0 Topics
	Tank Gauges Including Float-Type Tape Gauges In this section, we concentrate on types of automatic tank gauge (ATG) designs that are not detailed in the other sections	0 Posts 0 Topics
	Ultrasonic Level Detectors Ultrasonic level transmitters operate by generating an ultrasonic pulse and measuring the time it takes for the echo to return. If the transmitter is mounted at the top of the tank, the pulse travels in air (at a speed of 1087 ft/sec at 32 ° F, or 331 m/sec at 0 ° C)	0 Posts 0 Topics
	Vibrating Level Switches Several level switch designs operate by keeping a probe or other element in oscillation or in natural frequency vibration and triggering a relay when the process material in the tank reaches the vibrating element and damps out the vibration	0 Posts 0 Topics

Level Measurement ways