Homework SourseIf the second order term beta 0 of the thermocouple in ques
Solution
A tachometer is a device that is used for measuring the total revolutions per minute of the drive shaft and this way determining the speed of that shaft. The working principle of an electronic tachometer is quite simple. The ignition system triggers a voltage pulse at the output of the tachometer electromechanical part whenever the spark plug fires. The electromechanical part responds to the average voltage of the series of pulses. It shows that the average voltage of the pulse train is proportional to engine speed. The signal from the perception head is transmitted by standard twin screened cable to the indicator.
Types of Tachometer
Analog Tachometer
These Tachometers are very simple and it is easy to determine speed from these Tachometers .These comprises of needle giving the current reading and have marking that show safe and dangerous level Comprise a needle and dial-type of interface. They do not have provision for storage of readings and cannot compute details such as average and deviation. Here, speed is converted to voltage via use of an external frequency to voltage converter. This voltage is then displayed by an analog voltmeter. .They cant store the readings and compute details like deviation and average.
For eg.
Tachometers of bikes and 2 wheeler vehicles are analog in nature that show output in numerical form i.e Car speed .
D.C Tachometer
D.C means Direct Current .This tachometer is basically a permanent magnet generator .The output of this types of instrument is 2 to 10 volts per 1,000 rev per min (RPM) .For the purpose of Speed indication , a voltmeter with a high resistant value is built with calibration in RPM .
AC Tachometer
AC is for alternating current. This device consist of revolving permanent-magnetic field with a stationary winding. The voltage output and frequency that is generated remains in proportion rotation speed.
Mechanical Tachometer
This tachometer is very simple in construction .Mechanical tachometer is nothing but a linkage of shafts, gears and rotating weights
Digital tachometers
These consist of LCD or LED readout .They also have a memory for storage.( Major advantage over Analog type ) .These are used to perform statistical operations and gives precision measurement. Comprise LCD or LED readout and a memory for storage. These can perform statistical operations, and are very suitable for precision measurement and monitoring of any kind of time based quantities. Digital tachometers are more common these days and they provide numerical readings instead of using dials and needlesDigital tachometers are getting more preference these days as they provide accurate reading in numerical form instead of using dials and needles .
E.g Nowadays tachometer used in cars are numerical in nature
Contact tachometers
The tachometers that remain in contact with the rotating shaft are of contact type . It is generally preferred where it needs to be fixed with the machine . The contact type is in contact with the rotating shaft. The non-contact type is ideal for applications that are mobile, and uses a laser or optical disk. In the contact type, an optical encoder or magnetic sensor is used. Both these types are data acquisition methods An optical encoder or magnetic sensor is used in this type of Tachometer.
Non contact type
These Tachometers do not need to be in physical contact with the rotating shaft .The main application non-contact type is in mobiles, a laser or optical disk.
