Introduction to tachometer, types, block diagram, working principle, applications and uses.

1. Tachometer

2. Introduction
 A tachometer (revolution-counter, tach, rev-counter, RPM
gauge) is an instrument measuring the rotation speed of a
shaft or disk, as in a motor or other machine.
 The device usually displays the revolutions per minute (RPM)
on a calibrated analogue dial, but digital displays are
increasingly common.

3. Types Of Tachometers
 Analog Tachometers
 Digital Tachometers
 Contact and Non-Contact
Tachometers
 Time and frequency
measuring tachometers
Analog Tachometer
Digital Tachometer

4. Block Diagram

5. Working principle
• Pulses are fed to the tachometer at the
frequency to be measured. A scale factor is
applied to produce readings of desired types
(linear speed, flow rates, etc)
• Two basic principles:-
1. Principle of fixed time based tachometer
2. Principle of reciprocal tachometer

6. Working Principle
 The ignition system triggers a voltage pulse at the output of
the tachometer electrochemichal part whenever the spark
plug fires.
 The electrochemical part responds to the average voltage of
the series of pulses.
 It shows that the average voltage of the pulse train is
proportional to the engine speed.
 The signal from the perception head is transmitted by
standard twin screened cable to the indicator.
 The tachometers are temperature compensated to be able to
handle operations over a range of -20 to +70 degrees.

7. Applications
 Automobiles
 Laser Instruments
 Analog Audio Recording
 Medical Applications

8.  The tachometer in a vehicle enables the driver to select suitable
throttle and gear settings for the driving conditions.
 It enables the driver to prevent exceeding speed capability of sub-
parts such as spring retracted valves of the engine, and
overheating, thereby causing unnecessary wear or permanent
damage and even failure of engines
Uses