Types of measuring instruments
Measuring Instruments
•
Deflection and null type instruments
•
Analog and digital instruments
•
Active and passive instruments
•
Automatic and manually operated
instruments
•
Contacting and non contacting instruments
•
Absolute and secondary instruments
•
Intelligent instruments.
Deflection
and Null Type:
•
Physical effect generated by the
measuring quantity
•
Equivalent opposing effect to nullify
the physical effect caused by the quantity
Analog
and Digital Instruments:
•
Physical variables of interest in the
form of continuous or stepless variations
•
Physical variables are represented by
digital quantities
Active
and Passive Instruments:
•
In active, the quantity to be measured
activates some external power input source, which input produces the output.
Here additional external energy is required.
•
In passive, the output is produced
entirely by the quantity being measured.
Automatic
and Manually Operated:
•
Manually operated – requires the service
of human operator
•
Automated – doesn't requires human
operator
Contacting
and Non Contacting Instruments:
•
It has contact with the measuring medium
while measuring.
•
Measure the desired input even though
they are not in close contact with the measuring medium.
Absolute
and Secondary Instruments:
•
Absolute instrument shows reading in
terms of physical constant of instrument. They are used for calibration of
other instruments. Ex. Tangent galvanometer, Rayleigh Current balance.
•
Deflection of the instruments can read
directly in terms of electrical quantity like voltage, current, power,
frequency and etc… they are calibrated using standard instruments.
Some other Classification of measuring instruments:
1. On the basis of function
•
Length
measuring instruments
•
Angle
measuring instruments
•
Geometrical
form checking instruments
•
Surface
finish checking instrument
2. On the basis of accuracy
•
Most
accurate instruments ( Eg- High interference instruments)
•
Moderate
accurate instruments ( Eg- Comparator)
•
Below
moderate accurate instruments( Eg- dial indicator)
3. On the basis of precision
•
Precision
measuring instrument
•
Non-precision
measuring instrument
