Skip to main content

MECHANICAL COMPARATORS AND ITS WORKING

 A Mechanical comparator employs mechanical means for magnifying the small movement of the measuring stylus brought about due to the difference between the standard and the actual dimension being checked.

Mechanical comparators operating essentially on the same principle are available in different designs. They are : Sigma,  Mercer, Mikrokator, etc. The method of  magnifying small movement of the stylus in all mechanical comparators is effected by means of levers, gear-trains or a combination of these elements. Mechanical comparators are available having magnifications from 300 to 5000 to 1, and used mostly for inspection of  small parts machined to close limits. 

Dial Indicators may be classified as mechanical comparators as they have multiplying mechanism which greatly magnifies on the dial any movement of the indicator. 

    

mechanical comparators


Dial Indicators . The essential parts of the instrument is like a small clock with a plunger projecting at the bottom. Very slight upward pressure on the plunger moves it upward and the movement is indicated by the dial pointer. The dial is graduated into 100 divisions. A full revolution of the pointer about this scale corresponds to 1  mm travel of the plunger. Thus, a turn of the hand by the one scale division represents a spindle travel of 0.01mm. A revolution counter or a small dial to indicate the travel of the plunger through whole millimeters is sometimes incorporated in the gauge on the big dial. 

Movement of  stem 1 is transmitted by means of  an toothed rack through a compound gear train 2 and  3 to a pointer 4, which moves around a dial face. The required measuring pressure is provided by small spring incorporated in the mechanism. 

The Indicator is adjusted to zero by either turning the rim of the dial, or turning the head of the plunger while holding the dial stationary. 

Dial Indicators are available for ranges of measurement of 0 to 3 , 0 to 5  and 0 to 10 mm. These measurements indicate total movement "lift" of the plunger.

Dial gauges or dial indicators are used to true and align machine tools , fixtures and work , to test and inspect the size and trueness of a finished work to an accuracy of 0.01 mm. In English measurement dials are graduated in 0.001 in and some in 0.0001 in. They are also used in conjunction with other measuring instruments , e.g. inside calipers, depth gauges, etc, to measure inside and outside dimensions, errors in parallelism, flatness, etc. 


Other Common Types of  Comparators :

* Electrical Comparators. 

* Optical comparators. 

* Pneumatic Comparators. 

Labels:

Comments

Post a Comment

Popular posts from this blog

THROTTLE GOVERNING OF STEAM TURBINES

Steam Pressure at inlet to a steam turbine is reduced by throttling process to maintain the speed of the  turbine constant at part load and hence this method of governing is called "Throttle Governing".  Construction : Throttle governing system consists of  a centrifugal governor, a lever , an oil pump , a pilot piston , control valve , a relay piston and a throttle valve. The throttle valve is moved by a relay piston. The relay piston is actuated by pilot piston control valve. There are two piston valves covering ports in the pilot piston control valve without any overlap. These piston valves are operated by lubricating oil supplied by a gear pump at 2 to 4 bar. The oil returns to the drain from this chamber.  Working : When the turbine works on full rated load, the throttle valve will remain open. When the load is decreased, the energy output of the turbine becomes in excess and the turbine shaft speed increases. Hence, governor sleeve will lift. The upward movement of the
Post a Comment
Read more

ELECTRICAL COMPARATORS AND ITS WORKING

Electrical Comparators are used as a means of  detecting and amplifying small movements of a work contacting elements. An electrical comparator consists essentially of  a pick-up head or transducer for converting a displacement into a corresponding change in current and a meter or recorder connected in the circuit to indicate the electrical change, calibrated to show in terms of displacement. Generally, an amplifier is needed to provide the requisite sensitivity and to match the characteristics of different parts of  the circuit. Electrical comparators can be classified according to the electrical principle used in the pick-up head. Most of the comparators use either a differential transformer, an inductance bridge, a strain gauge or a capacitor as a means of detecting movement of the gauging element. There are different types of  electrical comparators. One kind called an electrolimit gauge is used to check or measure the outside diameter of a  roll. The object to be checked is place
Post a Comment
Read more

Advantages And Disadvantages Of Air Refrigeration System :

 Advantages Of  Air Refrigeration : 1. The refrigerant used namely air is cheap and easily available. 2. There is no danger of fire or toxic effects due to leakages. 3. The weight to ton of refrigeration ratio is less as compared to other systems. Disadvantages Of Air Refrigeration : 1. The quantity of  Refrigerant used per ton of refrigeration is high as compared to other systems. 2. The COP of the system is very low. Therefore running cost is high. 3. The danger of frosting at the expander valves is more as the air contains moisture content. 
Post a Comment
Read more