Page 92 - CITS - Electronic Mechanic - TT - 2024

ELECTRONICS MECHANIC - CITS

Case III when the core is moved to downward of null position (for displacement to the downward of the reference
point)
The amount of change in voltage either amount of movement of core and indicates amount of linear motion.
The output voltage of an LVDT is linear function of core displacement .

Advantages of LVDT:
High range- The LVDTs have a very high range for measurement of displacement .They can used for measurement
of displacement s ranging for 1.25mm to 250mm
High input and high sensitivity-The output of LVDT is so high that it does not need any amplification .The
transducer possesses a high sensitivity which is typically about 40v/mm.
Low power consumption -The power is about 1w which is very as compared to other transducers.
Disadvantages of LVDT

LVDT is sensitive to stray magnetic fields so it always requires a setup to protect them from stray magnetic fields.
LVDT gets affected by vibrations and temperature.
Proximity Sensor
“Proximity Sensor” includes all sensors that perform non-contact detection in comparison to sensors, such as
limit switches, that detect objects by physically contacting them. Proximity Sensors convert information on the
movement or presence of an object into an electrical signal.
Working Principle of Inductive Proximity Sensors

Inductive Proximity Sensors detect magnetic loss due to eddy currents that are generated on a conductive
surface by an external magnetic field. An AC magnetic field is generated on the detection coil, and changes in the
impedance due to eddy currents generated on a metallic object are detected. Other methods include Aluminum-
detecting Sensors, which detect the phase component of the frequency, and All-metal Sensors, which use a
working coil to detect only the changed component of the impedance. There are also Pulse response Sensors,
which generate an eddy current in pulses and detect the time change in the eddy current with the voltage induced
in the coil. The sensing object and Sensor form what appears to be a transformer-like relationship

Working Principle of Capacitive Proximity Sensors
Capacitive Proximity Sensors detect changes in the capacitance between the sensing object and the Sensor. The
amount of capacitance varies depending on the size and distance of the sensing object. An ordinary Capacitive
Proximity Sensor is similar to a capacitor with two parallel plates, where the capacity of the two plates is detected.
One of the plates is the object being measured (with an imaginary ground), and the other is the Sensor’s sensing
surface. The changes in the capacity generated between these two poles are detected. The objects that can be
detected depend on their dielectric constant, but they include resin and water in addition to metals.

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CITS : E & H - Electronics Mechanic - Lesson 43 - 47