Rotary Variable differential transformer (RVDT)
RVDT transducer is similar to the LVDT in their work but just used to measure angular displacement. inside of this, we use a rotary shaft instead of the movable iron rod. RVDT is an electromechanical transducer whose output is the ac Voltage and this output voltage is directly proportional to the angular displacement. In RVDT there are no electronic components inside it, it is an AC-controlled device. RVDT has a very high accuracy level.
Rotary Variable differential transformer
RVDT is designed to measure the angular displacement so we can also be called it an angular position sensor. it is a passive transducer.
Capacitive transducers:- A capacitive transducer is also used to measure the displacement of any physical body we can measure the displacement up to serval meter using the capacitive transducer with the good stability and high speed under various environmental conditions and variations
Generally, we use the parallel-plate capacitor as a transducer. And as we know the capacitance formula of a capacitor is
So here, there is three type of variation that happens in the capacitive transducer so we can measure the displacement by varying these 3 variations let's see one by one to each variation.
ϵ is the permittivity of the medium,
A is the area of the plates
d is the distance between two plates.
Changing the gap between the plate:- As we know that each capacitor is consist of a movable parallel plate, we can change the distance between them using some external configuration, and this variation in distance between the two plates is shown in the displacement and due to the change in the distance of parallel plate there is a change in the capacitance because capacitance is directly propositional to the change in distance, and we can measure the capacitance using some circuit arrangement.
Changing the gap between two parallel plate
Changing the area between the two plates of capacitor
displacement by changing the area between two movable plates.
here we can establish some mechanism to measure the linear displacement, so simply we can connect any moving element that causes the change in the area of these two capacitive plates.
In this capacitive transducer, one plate is fixed in its position and the other is variable concerning the other plate, and this process affects the overlapping area of capacitive transducers.
Changing the permittivity of capacitor:- Here we can change the capacitance of the transducer by varying the dielectric material is called the permittivity of the capacitive transducer (ϵ). AS we know that the permittivity of the capacitive transducer is directly proportional to the capacitance of the transducer. here dielectric material is filled between the two parallel plates of capacitors so we can change the capacitance of the transducer by moving the arms, which are directly connected to the dielectric medium.
Advantages of Capacitive transducer
Disadvantages of Capacitive Transducers :
It can be effect by a stray magnetic field.
It requires some extra electrical circuitry to measure the change in capacitance.
Capacitance can be affected by changes in temperature variation
Measurement of Strain & Force
Now a day to measurement of strain and force is very essential to determine and examine the various parameters of any physical body. Measuring the strain and force in underground cavities, tunnels, buildings, concrete, bridges, and embedment in soil/concrete, etc is very important. The main purpose of measuring the strain of any physical body is to determine the variation with time, and quantitatively. So for the measurement of strain and force of any physical body use a strain gauge, here we will discuss every point of the strain gauge.
Strain gauge:- Strain gauge is a resistor-based electronics transducer that is used to measure the strain and force of any physical object. it's a passive electrical Transducer. The strain gauge was invented in 1938 by Edward E. Simmons & Arthur C. Ruge. The strain gauge is a very important and significant sensor that is used to measure the amount of strain of any physical object. When we applied any external force and strain on any physical object. So there is a change in the shape of an object. It's called the deformation of an object. and this deformation of any object happens in both compression and tensile of the object's body. This tensile and compression are measured by the strain gauge sensors.
The deformation of any physical object happens in its limited elasticity. Either object size or shape is increased, narrower and longer and becomes shorter and broadens As a result of it, there is a change in resistance of the object.