Principle of Various Comparators | Types of Comparator | Accuracy | Precision

Principle of Various Comparators

Types of Comparator.

1) Mechanical comparator.
2) Electrical Comparator.
3) Electronics Comparator
4) Pneumatic Comparator
5) Optical Comparator ( Optical lever )

Small information about this Comparators.


1) Mechanical comparator.
It works on the principle of converting lin,ear movement8  into 'mgular;using rack and pinion. It uses gear train for magnification and scale pointer as iridicating device.

      Now a days digital dial gauge  indicators are also, available.
Refer Fig.
 Examples of mechanical comparator.
1) Dial gauge.
2) Sigma comparator.
3) The Johansson mikrokator.
4) Reed type comparator.

2) Electrical Comparator.
   It works  on  mutual inductance principle. When core is inserted in a magnetic fields of primary windings, the voltage  induced  in'  secondary   is  proportional   to '  the    core position. Refer Fig.


3) Electronics Comparator
In electronics comparator, a transducer is used to pick up signals (displacement) and amplified using amplifier, which  are read-out using indicating devices. Refer Fig.

4) Pneumatic Comparator
— Pneurnatic cotnparators work on back pressure gauge.
— Air flows with a constant pressure through two orifices  as shown in Fig. P1 is the pressure upstream of the first orifice and P2 is the pressure between two onfice, P1  is equal to P2 when O2 ls blocked Also it terids to zero as O2 is increased uptot infinity Also P2 depends                                                                                     upon L.   Refer Fig.

5) Optical Comparator ( Optical lever )

— . This  principle is applicable  to most of optical instruments.
— When reflector itself is tilted by a small angle α, the reflected ray from reflector will tilt by 2α is the principal of optical lever ( optical Comparator ). Refer Fig.

Here some information about accuracy and Precision.

Accuracy

~ Accuracy of an indicated (measured) value may be defined as conformity with or closeness to an accepted value (standard). Accuracy of the measured signal depends upon the intrinsic accuracy of instrument
itself, variation of the signal being measured.
~ The difference between the measured value (Vm) and the true value (V of the quantity represents static error.
~ The accuracy rating can be expressed in a following form :
(a) Accuracy is expressed in terms of measured value :
e.g. The thermometer may be stated to read
within ± 0.5° C between 100° C and 2000 C
Permissible lower 100° C ±0.5° C
reading 1.e
99.50C or 100.50 C
Permissible
2000 C ± 0.50 C
higher reading i.e.
199.5°C or 200.5°C

Precision :

Define: Precision.
~ Precision is also concerned with measurement.
~ Precision is defined as the repeatability 0f measuring process.
~ Precision has not any meaning for 0nly one measurement, but it exists for a set of measurements.
~ If for different readings of measurement values are varied by small amount than average value and if lesser variations are present, called as precision measuring system. e.g. Readings of a jobs with true
value 10.00 mm which are accurate are 10.001 mm, 10.000 mm, 10.001 mm, 9.999 mm, 9.999 mm, 10.000 mm, 10.001 mm.