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what is inductive transducer ?
what is inductive transducer ?
· Inductive Transducer can be categorized as :
· Self generating :
Ø Voltage is generated due to the relative motion between conductor and a magnetic field
Ø Classification: i) electromagnetic type, ii) Electrodynamic Type, iii) Eddy current Type
Ø Example: Tachometer, which directly converts speed or velocity into an electrical signal
· Passive:
Ø Require an external source of power.
Ø Motion of an object results in changes in the inductance of the coils of the transducer
Ø Example: An inductive electromechanical transducer converts physical motion into a change in inductance.
Change in self inductance with number of turn and permeability
Change in self inductance with number of turn and permeability
Figure 7.4.1 : inductive tranducer (a) linear (b) angular
• Figure 7.4.1 (a) and (b) are transducers used for the measurement of displacement of linear and angular movement respectively.
• In both cases, as the number of turns are changed, the self inductance and the output also changes.
Inductive Transducer: Variable Reluctance
Variable reluctance transducer
• The transducer consists of a coil wound on a ferromagnetic core.
• The displacement which is to be measured is applied to a ferromagnetic target.
• The core and the target are separated by an air gap.
• The self inductance of the coil is inversely proportional to the length of the air gap.
• When the target is near the core, the length is small, thus increases the self inductance.
Inductive Transducer: LVDT
Inductive Transducer: LVDT
The LVDT full form is “Linear Variable Differential Transformer” is LVDT. Generally, LVDT is a normal type of transducer. The main function of this is to convert the rectangular movement of an object to the equivalent electrical signal. LVDT is used to calculate displacement and works on the transformer principle.
The LVDT sensor diagram comprises a core as well as a coil assembly. Here, the core is protected by the thing whose location is being calculated, while the coil assembly is increased to a stationary structure. The coil assembly includes three wire-wound coils on the hollow shape. The inside coil is the major, which is energized by an AC source. The magnetic flux generated by the main is attached to the two minor coils, making an AC voltage in every coil.
The main benefit of this transducer, when compared with other LVDT types, is toughness. As there is no material contact across the sensing component.
Because the machine depends on the combination of magnetic flux, this transducer can have an unlimited resolution. So the minimum fraction of progress can be noticed by an appropriate signal conditioning tool, and the transducer’s resolution is exclusively determined by the declaration of the DAS (data acquisition system).
Video
Video
EXAMPLES
EXAMPLES
1) An AC LVDT has the following data. Input = 6.3 V, output = 5.2 V, range ± 0.5 in. Determine:
i) the output voltage vs core position for a core movement going from +0.45 in to -0.30 in.
ii) the output voltage when the core is -0.25 in from the centre.
Solution:
i) Total distance = 1in
1in=5.2V, +0.45=2.34V, -0.3in=-1.56V
𝑉𝑜 = 𝑉0.45𝑖𝑛 − 𝑉−0.3𝑖𝑛
= 2.34 − −1.56
= 3.9𝑉
ii) -0.25in=-1.3V
2) In a linear LVDT the output voltage is 1.8V at maximum displacement. At a certain load of deviation from linearity is maximum and it is ± 0.0045𝑉 from the straight line through the origin. Find the linearity of the given load.
Solution:
%𝑙𝑖𝑛𝑒𝑎𝑟𝑖𝑡𝑦 = ± 0.0045𝑉 1.8 × 100
= ±0.25%
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