General Purpose LVDT: for use in many industrial and research applications. FIG1– LINEAR VARIABLE DIFFERENTIAL TRANSFORMER • THE TRANSFORMER CONSISTS OF A SINGLE PRIMARY WINDING P1 AND TWO SECONDARY … ... Hydrogen annealing is done on Iron core to reduce harmonics, residual voltage of core and thus provides high sensitivity. The output from a linear variable differential transformer is a direct, linear function of the input for its specified measuring range. The half-bridge LVDT does not produce a null voltage, and the A/B ratio represents the range-of-travel of the core. As the name suggests, many people get confused that it is a Transformer. Definition of LVDT. Differencing the two secondary voltages results in a voltage proportional to the core’s distance from null. An LVDT (linear variable differential transformer= is an electromechanical sensor used to convert mechanical motion or vibrations, specifically rectilinear motion, into a variable electrical current, voltage or electric signals, and the reverse. Characteristics of LVDT & its significance Characteristics of LVDT Significance:-As the core is moved in one direction from the null position, the differential voltage i.e. The complex nature of the transformer is also having a phase angle of either 0 or 180 degrees whenever the core is far away from the null position. The resulting higher voltage of the first secondary in relation to the second secondary causes an output voltage that is in phase with the primary voltage. To reduce the eddy current losses, the core is provided with a slot. The output across secondary of this transformer is the differential thus it is called so. the difference of the two secondary voltages will increase while maintaining an in-phase relationship with the voltage from the input source. 2. In Figure 1, as the core moves over S1, the voltage output of … Ideally, the output voltage at the null position should be equal to zero. Types of LVDT based on applications: 1. Laminated core is also used for the same purpose. The term LVDT stands for the Linear Variable Differential Transformer.It is the most widely used inductive transducer that converts the linear motion into the electrical signal.. It is very accurate inductive transducer as compared to other inductive transducers. LVDT full form is Linear Variable Differential Transformer. The effective voltage and LVDT output is the difference between each secondary. However, it is possible to use an LVDT beyond its specified measuring range, with a predefined table or polynomial function that provides compensation for the nonlinearity. As the core moves to one side of the null position, the magnitude of one secondary becomes greater than the other. Figure 6: Half-bridge LVDT configuration Note that the LVDT concept can be implemented in rotary form, in which case the device is called a rotary variable differential transformer (RVDT). • Slotted longitudinally to reduce eddy current losses. CONSTRUCTION OF LVDT Soft iron cor e • Made of high permeability nickel iron alloy which is hydrogen annealed providing low harmonics, low null voltage & high sensitivity. However, in actual practice, there exists a small voltage known as Residual Voltage, at the null position. When the core moves away from the center of the LVDT, known as the null point, the signal from the primary will be coupled to one secondary more than the other. The maximum value of E OUT occurs at maximum core displacement from null (center) position and is a function of the amplitude of the primary-side excitation voltage and the sensitivity factor of the particular LVDT; typically, it is fairly substantial at several volts (RMS). Cross-Sectional View of LVDT Core and Windings Displacing the core to the left (Figure 4) causes the first secondary to be more strongly coupled to the primary than the second secondary. This slot cut the magnetic field created hence reducing the flux. The residual voltage is because of the complex nature of the electrical model of a linear variable differential transformer which comprises of parasitic capacitances of the windings. This causes power loss in the core. An LVDT is designed to have symmetric measurement ranges on each side of null. 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