1. MEASUREMENT AND INSTRUMENTATION
R.HARIHARAN
Lecturer/EEE

2. UNIT - 4 STORAGE AND DISPLAY DEVICES Magnetic disk and tape Recorders
digital plotters
Printers
CRT display
digital CRO
LED
LCD
dot matrix display.

3. 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.

5. 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.

6. Basic Components of Tape recorder
Recording Head
Magnetic Head
Reproducing Head
Tape transport mechanism
Conditioning device.

7. Methods Of Magnetic Tape recording
Direct Recording
FM recording
Pulse Duration Modulation Recording

8. Printers
Classification
Impact printers
Non Impact Printers.

9. Impact printers Line Printer Drum Printer. Chain Printer.
Dot Matrix Printer

10. Non Impact Printers. Ink jet Printer Laser Printer
Thermal Transfer Printer

11. 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.

14. 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.

15. 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.

16. 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.

17. 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.

18. Dot Matrices 3x5 dot matrix Dot matrix utilizing 27 Dots

19. THANK YOU