Advanced Measurement Systems and Data Analysis | Assignment

Advanced Measurement Systems and data analysis
1)
The largest total linear dimension of a component which is manufactured by the company =
400 nm
Tolerance ( of products ) = 50 um
Tolerance ( of precision spindles ) = 5 microns
Surface roughness = 12.5 – 0.025 um
Types of equipment for improving the measurement as well as product quality in the
company :
In surface metrology, the small scale features are measured on a surface. The major
parameters considered are
: surface roughness, fractality and surface primary form. The choice of correct instrument for
measurement based on the application is necessary. Interferometry shows large value of
vertical resolution. In digital holography, moving samples and deformable surfaces are
measured. It can measure vibrations also. The focus variation can be used for rough surfaces
and not smooth surfaces ( like Silicon wafer ). It can be used for the samples of metal, plastic
or paper. In confocal microscopy, the lateral resolution is good but the measurement on steep
flanks is not possible. In confocal chromatic aberration, the measurement of rough as well as
smooth surfaces is possible. In contact profilometer, lateral resolution is very good but the
surface contamination may occur due to contact ( Hanchett, 2012 ).
If the number of roughness parameters is more, then the accuracy is more. The 3 types of
parameters are – amplitude, spacing and hybrid parameters.
Sensors :

Operating Principle :
A sensor is a device which can help in detection of any change and can send this data to an
electronic device ( like a processor ). The sensors can be used to measure the physical as well
as chemical properties of a material. The sensors can also be built on a microscopic scale by
the MEMs technology ( micro sensors ).
Characteristics :
There may be some deviation in the sensor output which can decrease its accuracy. The
reasons for this deviation can be : scale range, sensitivity, offset or bias, non – linearity,
dynamic error, drift, noise, hysteresis error, quantization error, aliasing error etc ( Inga ,
2014 ).
Performance :
The sensor must be sensitive to the property being measured and insensitive to the other
properties. It must not change the property being measured.
Transducers :
Operating Principle :
The device which can convert energy from one form to the other is referred to as a
transducer. Transducers are generally used to convert the electrical energy into any other
physical quantity ( like light, force, torque etc. ) or vice versa.
Characteristics :

A transducer has the following characteristics : Dynamic range, repeatability , noise and
hysteresis. The dynamic range is given by the ratio of the largest signal amplitude to the
smallest signal amplitude which can be translated by the transducer. If the dynamic range is
more, then the sensitivity and precision are also more. If a transducer is able to get similar
output on simulation with same input, then it has good repeatability. A transducer also adds
random noise to the output. Smaller signals are affected more due to the noise. Hysteresis in a
transducer refers to the phenomenon where the output is dependent on current as well as past
input ( Zhou, 2016 ).
Performance :
The transducers can be of 2 types – Mechanical transducers and electrical transducers. The
mechanical transducer converts a physical quantity into a mechanical quantity. The electrical
transducer converts a physical quantity into an electrical quantity. For example – LVDT
( Linear Variable Differential Transformer ) which is capable of measuring the displacement.
LVDT :
The LVDT ( Linear variable differential transducer ) can be used for the measurement of
displacement.
Optical encoder :
The optical encoder is a device of electromechanical nature. It gives the output in electrical
form which gives digital data proportional to the input shaft’s angular position. The optical
encoder is a type of sensor which senses the angular position. The shaft is coupled
mechanically to the input driver. A disc is fixed rigidly to it which gets rotated. The surface
of the disc is marked with the segments successively which are of 2 types - Clear and opaque.
The clear or transparent segments present in the rotating disc allow the light emitted by
diodes (which emit infra red light) to reach the infrared receivers. This leads to the generation

of an analog signal. This analog signal is passed through an amplifier and then converted to
digital format. The data is then passed to a data processor.
The operating principle of an optical encoder can be understood in 3 parts : Encoder shaft
mechanics, Engraved disc optics and reading and output signal electronics ( Zanobini,
2016 ).
CMM ( Co – ordinate measuring machine ) :
CMM is used for testing an assembly or a part as per the design specification. The generation
of point clouds can be used for constructing the feature by analysis using the regression
method. An operator can manually position the probe or it can be an automated process for
the collection of the points. The programming for CMM can be done in such a manner that it
can give the measurement of similar parts repetitively. An industrial robot can be assumed to
be a special type of CMM which uses automation. A CMM consists of 3 major parts. They
are: the system for probing, the system for collecting and reducing data and the main frame
having the 3 axis of movement. The frame which moves can be made up of steel, granite,
Aluminium alloys, ceramics or Silicon carbide. The Z axis for CMM must have good
stiffness ( Janiszewski, 2012 ).
Operating Principle :
A probe is used in this device to sense the points discretely which are present on an object’s
surface. This helps in the measurement of the geometry of an object under consideration. The
probe can be chosen from various types- laser,optical, mechanical, White light etc.
The position of the probe can be controlled in 2 ways- by a computer or by an operator in a
manual fashion. The position of the probe is specified with respect to a reference point in the
3- dimensional space. The displacement from this reference point is considered. The position
is specified in Cartesian coordinate system (as x,y and z).
In the 3-dimensional bridge CMM, the probe can be moved in 3 directions of x,y and z axis
that are mutually perpendicular to one another. There is a sensor present on every axis for