What is linear variable differential transformer (LVDT) ?

Engineer

(LVDT).

Study of linear variable differential transformer (LVDT).

Theory : This is the most widely used inductive transducer. To translate the linear motion into electrical signals.

★ Construction of LVDT :-

 

• The basic construction of LVDT shows the transformer consist of a single primary winding (p) and two secondary winding S1 & S2 wound on a cylindrical former.

 • The secondary winding have equal no. of turns and are identially placed on either side of the primary winding.

• Primary winding is an connected to an ulternating current source.

• A movable soft iron are is placed inside the formers. The displacement to be measured is applied to the arm attached to soft iron core.

• A assembly is placed in strainless steel housing. The frequency of the AC applied to primary winding may be between 50H2 to 20H2.

(LVDT).

Working :-Primary winding is excited by an ulternating current source, it includes AC voltages in two secondary windings.

                  Output voltage of secondary S1 is es1 and the secondary S2 is es2. differntial output voltage is given by 

                   e0 = es1  es2

  Now , 3 case arises according to the locations of core which explains the working of LVDT .

★  Case 2 :- If core is moved to the left of null position, more flux links with winding S1 and less with winding S2. The magnitude of output voltage is inface with  the primary winding. 

★ Case 3 If the core is moved right of the null position , the flox linking with winding s2 becomes largers then that linking with winding s1 and the output voltage is 180˙ out the face with primary voltage .

★ Result : The difference of two voltages appears across the output terminals of the transducer and gives a measure of the physical position of the core and hence, the displacement. By comparing the phase of the output voltages with the source, direction of the movement of the core and  hence of displacment may be determine.

(LVDT).

A Linear Variable Differential Transformer (LVDT) is a type of electrical transducer used to measure linear displacement or position. It is a highly accurate and reliable device commonly employed in various industrial and scientific applications.

The LVDT consists of a primary coil, two secondary coils, and a movable core. The primary coil is energized with an alternating current (AC) signal, typically at a high frequency. The two secondary coils are symmetrically wound on either side of the primary coil, and they are connected in series opposition.

The movable core, usually made of ferromagnetic material, is placed within the hollow center of the coils. As the core moves linearly, it induces varying voltages in the secondary coils due to electromagnetic coupling. The magnitude of the induced voltage in each secondary coil is proportional to the displacement of the core.

The operation of an LVDT is based on the principle of electromagnetic induction. When the core is perfectly centered within the coil assembly, the induced voltages in the secondary coils are equal, and they cancel each other out, resulting in a zero net output voltage. This center position is called the null position.

However, when the core moves away from the null position, the voltages induced in the secondary coils become imbalanced. The amplitude and phase of the output voltage depend on the direction and magnitude of the displacement. By measuring the output voltage, the position or displacement of the core can be accurately determined.

(LVDT).

LVDTs offer several advantages, including high accuracy, linearity, and long-term stability. They can operate over a wide range of frequencies and temperatures, making them suitable for various applications. LVDTs are commonly used in industrial automation, robotics, aerospace, and scientific research for position feedback, dimensional gauging, and control systems.

In summary, an LVDT is an electrical transducer that converts linear displacement or position into an electrical signal. It utilizes electromagnetic induction to generate an output voltage proportional to the position of a movable core within a coil assembly. LVDTs are known for their accuracy, reliability, and wide range of applications in various industries.