Difference between revisions of "Vibrating Rod Level Sensors"

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Vibrating Rod Level Sensors (view source)

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[[Category:Detectors, Sensors]]{{Knoppen}}  
[[Category:Detectors, Sensors]]{{Knoppen}}  
[[File:Vibrating Rod Level Sensors.jpg|thumb|right|Vibrating Rod Level Sensors]]
'''Vibrating Rod Level Sensors''' is a piezoelectric driven vibration type level switch that detects high, mid and low level in [[Bins]], [[Silos]], and [[Hoppers]] filled with powders or dry bulk solid materials.


Level sensors detect the level of substances that flow, including liquids, slurries, granular materials, and powders. Fluids and fluidized solids flow to become essentially level in their containers (or other physical boundaries) because of gravity whereas most bulk solids pile at an angle of repose to a peak. The substance to be measured can be inside a container or can be in its natural form (e.g., a river or a lake). The level measurement can be either continuous or point values. Continuous level sensors measure level within a specified range and determine the exact amount of substance in a certain place, while point-level sensors only indicate whether the substance is above or below the sensing point. Generally the latter detect levels that are excessively high or low.
 
There are many physical and application variables that affect the selection of the optimal level monitoring method for industrial and commercial processes. The selection criteria include the physical: phase (liquid, solid or slurry), temperature, pressure or vacuum, chemistry, dielectric constant of medium, density (specific gravity) of medium, agitation (action), acoustical or electricalnoise, vibration, mechanical shock, tank or bin size and shape. Also important are the application constraints: price, accuracy, appearance, response rate, ease of calibration or programming, physical size and mounting of the instrument, monitoring or control of continuous or discrete (point) levels.
==Principle of operation==
The vibrating rod level sensors are  piezoelectric devices with a single rod shaped vibrating  element. The rod of the sensor vibrates if there is no  material covering the active rod. When the rod  is covered with material, the vibration is dampened  and an electronic circuit forces  a relay to switch. When the rod gets  uncovered, the vibration will restart and the relay will switch back. The rod is fixed at two  points in a way that it forms a perfect swinging-  system with very low mechanical losses . If you hit the end of the rod, it will vibrate on its resonance frequency and ring  like a tuning fork. In action, the vibration is driven by a  piezo system, which gets electrical pulses from the  electronics. These electric pulses enlarge the size of the  piezos which leads to a bowing of the rod. Since the pulses  are exactly on the frequency where the rod is in  resonance, the whole rod starts swinging. A second piezo  system works as a swinging detector. If the piezo gets  distorted, it gives a voltage signal to the electronics.  This way, the electronics can check if the rod is vibrating  or not.
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