MEASUREMENT AND
INSTRUMENTATION
K.ANISH
Lecturer/EEE
UNIT - 4
STORAGE AND DISPLAY DEVICES
 Magnetic disk and tape
 Recorders
 digital plotters
 Printers
 CRT display
 digital CRO
 LED
 LCD
 dot matrix display.
2
Recorders
A recorders records electrical and non
electrical quantities as a function of time.
They are used for having permanent records.
It monitors continuously the condition state or
value of the process variable such as flow,
force, pressure, temperature, current , voltage,
electrical power etc.
Current and voltage can be recorded directly
while the non electrical quantities are
recorded indirectly by first converting them to
equivalent currents or voltages with the help
of sensors or transducers.
Recording device
Analog recorders
Oscillographic recorders
Digital recorders
Magnetic tape recorders
Incremental digital
Graphic recorders
Strip Chart recorders
Galvanometer type
Null type
Potentiometric recorders
Bridge recorders
LVDT recorders
X-Y recorders
Circular Chart recorders
Synchronous digital
Magnetic Tape and Disc Recorders
 Magnetic tapes and magnetic discs are
essentially storage devices. A magnetic tape
is a thin dimensionally stable plastic coated
with iron oxide particles one side.
 Mechanism-The magnetic tapes or disc
passes under the gap, and the oxide particles
retain a state of permanent magnetization
proportional to the flux existing at that
instant , the particle leaves the gap.
Basic Components of Tape recorder
 Recording Head
 Magnetic Head
 Reproducing Head
 Tape transport mechanism
 Conditioning device.
Methods Of Magnetic Tape recording
 Direct Recording
 FM recording
 Pulse Duration Modulation Recording
Printers
Classification
Impact printers
Non Impact Printers.
Impact printers
1.
2.
3.
4.
Line Printer
Drum Printer.
Chain Printer.
Dot Matrix Printer
Non Impact Printers.
 Ink jet Printer
 Laser Printer
 Thermal Transfer Printer
Cathode Ray Oscilloscope (CRO)
 The cathode ray oscilloscope is a versatile
laboratory instrument used for display,
measurement and analysis of waveform.
 CRO are very fast X-Y plotter displaying an
input signal versus another signal or versus
time.
 The Stylus of this plotter is a luminous spot
which moves over the display area in
response to an input voltage.
 The luminous spot is produced by a beam of
electrons striking a fluorescent screen.
 Applications of CRO
 Sampling oscilloscopes.
 Storage oscilloscopes.
 An analog oscilloscope.
 Cathode ray tube (CRT)
 Electron gun assembly.
 Deflection plate assembly.
 Fluorescent screen.
 Glass envelope.
 Base through which connection are made to various
parts.
LED
 It is perhaps the most important of the
display device for use in instrumentation
systems.
 It is a PN junction device that emits light
when a current passes through it in the
forward direction.
 Charge carrier recombination occurs at PN
junction as electrons from N side
recombines with holes on P side.
Conti..
 When this happens ,charge carrier give up
energy in the form of heat and light.
 If the semiconductor material is translucent
the light is emitted and junction is source of
light.
 Charge carrier recombination takes place in
the P type material. For maximum light
emission a metal film anode is deposited
around edge of P Type material.
LCD
 Used in application of display of numeric
and alpha numeric characters in dot matrix
and segmental displays.
 Types
Dynamic scattering type
Field effect type.
Dot Matrices
 3x5 dot matrix
 Dot matrix utilizing 27 Dots
 5x7 dot matrix
THANK YOU
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