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Difference between revisions of "Load Cells"
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[[File:Load Cell1.jpg|thumb|right|Load Cell]] | [[File:Load Cell1.jpg|thumb|right|Load Cell]] | ||
'''Load Cell''' is used to convert a force into electrical signal. This conversion is indirect and happens in two stages. Through a mechanical arrangement, the force being sensed deforms a [[Strain Gauges|strain gauge]]. The strain gauge measures the deformation (strain) as an electrical signal, because the strain changes the effective electrical resistance of the wire. A load cell usually consists of four strain gauges in a Wheatstone bridge configuration. Load cells of one strain gauge (quarter bridge) or two strain gauges (half bridge) are also available. The electrical signal output is typically in the order of a few millivolts and requires amplification by an instrumentation amplifier before it can be used. The output of the transducer can be scaled to calculate the force applied to the transducer. | '''Load Cell''' is used to convert a force into electrical signal. This conversion is indirect and happens in two stages. Through a mechanical arrangement, the force being sensed deforms a [[Strain Gauges|strain gauge]]. The strain gauge measures the deformation (strain) as an electrical signal, because the strain changes the effective electrical resistance of the wire. A load cell usually consists of four strain gauges in a Wheatstone bridge configuration. Load cells of one strain gauge (quarter bridge) or two strain gauges (half bridge) are also available. The electrical signal output is typically in the order of a few millivolts and requires amplification by an instrumentation amplifier before it can be used. The output of the transducer can be scaled to calculate the force applied to the transducer. | ||
==Types== | ==Types== | ||
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===Others=== | ===Others=== | ||
Other types include '''Piezoelectric Load Cells''' , and '''Vibrating Wire Load Cells''', which are useful in geomechanical applications due to low amounts of drift, and capacitive load cells where the capacitance of a capacitor changes as the load preses the two plates of a capacitor closer together. Every load cell is subject to ringing when subjected to abrupt load changes. This stems from the spring-like behavior of load cells. In order to measure the loads, they have to deform. As such, a load cell of finite stiffness must have spring-like behavior, exhibiting vibrations at its natural frequency. An oscillating data pattern can be the result of ringing. Ringing can be suppressed in a limited fashion by passive means. Alternatively, a control system can use an [[Actuators|actuator]] to actively damp out the ringing of a load cell. This method offers better performance at a cost of significant increase in complexity. Load cells are used in several types of measuring instruments such as universal testing machines. | Other types include '''Piezoelectric Load Cells''' , and '''Vibrating Wire Load Cells''', which are useful in geomechanical applications due to low amounts of drift, and capacitive load cells where the capacitance of a capacitor changes as the load preses the two plates of a capacitor closer together. Every load cell is subject to ringing when subjected to abrupt load changes. This stems from the spring-like behavior of load cells. In order to measure the loads, they have to deform. As such, a load cell of finite stiffness must have spring-like behavior, exhibiting vibrations at its natural frequency. An oscillating data pattern can be the result of ringing. Ringing can be suppressed in a limited fashion by passive means. Alternatively, a control system can use an [[Actuators|actuator]] to actively damp out the ringing of a load cell. This method offers better performance at a cost of significant increase in complexity. Load cells are used in several types of measuring instruments such as universal testing machines. | ||
==Features== | ==Features== | ||
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* Insensitive to vibrations. | * Insensitive to vibrations. | ||
* Unique mounting arrangements. | * Unique mounting arrangements. | ||
==Sources== | ==Sources== | ||
[http://en.wikipedia.org/wiki/Load_cell Wikipedia Load Cells] | [http://en.wikipedia.org/wiki/Load_cell Wikipedia Load Cells] | ||