Different types of comparators

Comparators are precision measuring instruments used in various industries for accurate measurement and inspection of components. They are used to compare the dimensions of a workpiece with that of a standard reference and provide a precise measurement of the difference.

There are several types of comparators available, each with its own unique features and applications. Three common types of comparators are dial indicator, sigma comparator, and optical lever. However, an interferometer is not a type of comparator.

Dial indicator
- A dial indicator is a mechanical comparator that uses a plunger with a spring to measure linear displacement.
- It consists of a dial face with a needle that moves in response to the plunger movement.
- The dial is graduated in units of measurement, such as millimeters or inches, allowing precise measurements to be taken.
- Dial indicators are commonly used in manufacturing and engineering industries for dimensional measurements.

Sigma comparator
- A sigma comparator is an electronic comparator that uses a linear variable differential transformer (LVDT) to measure linear displacement.
- It consists of a LVDT probe that detects the displacement of a workpiece.
- The LVDT converts the displacement into an electrical signal, which is then amplified and displayed on a digital readout.
- Sigma comparators are highly accurate and widely used in industries where precise measurements are required.

Optical lever
- An optical lever is a non-contact type of comparator that uses laser interferometry to measure linear displacement.
- It consists of a laser source, beam splitter, and detector.
- The laser beam is split into two separate beams, one of which is directed towards the workpiece and the other towards a reference mirror.
- The reflected beams are recombined and interference patterns are generated.
- By measuring the interference patterns, the displacement of the workpiece can be determined.
- Optical levers are used in industries where high precision measurements are required, such as semiconductor manufacturing and research laboratories.

Interferometer
- An interferometer is not a type of comparator, but rather a device used to measure wavelengths, distances, and surface irregularities.
- It works on the principle of interference of light waves to determine the phase difference between two or more beams.
- Interferometers are used in various scientific and industrial applications, such as optical testing, metrology, and astronomy.

In conclusion, the correct answer is option D - Interferometer, as it is not a type of comparator but a separate measurement instrument used for different purposes.