* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download magnetic
Survey
Document related concepts
Three-phase electric power wikipedia , lookup
Pulse-width modulation wikipedia , lookup
Electrical ballast wikipedia , lookup
Power inverter wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Electric machine wikipedia , lookup
Stray voltage wikipedia , lookup
Power electronics wikipedia , lookup
Brushed DC electric motor wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Alternating current wikipedia , lookup
Buck converter wikipedia , lookup
Induction motor wikipedia , lookup
Stepper motor wikipedia , lookup
Voltage regulator wikipedia , lookup
Opto-isolator wikipedia , lookup
Mains electricity wikipedia , lookup
Transcript
EXPERIMENT NO. AIM: Measurement of speed using magnetic pick up. APPARATUS: Trainer kit , CRO , connecting wires THEORY: A magnetic pick up is a coil placed in magnetic field. Variation in magnetic field induces a voltage pulse in the coil. Amplitude and frequency of induced voltage pulse depends upon rate of change of magnetic flux. Magnetic flux produced by magnet can be altered by bringing any external magnetic material near to the magnetic field of magnet which will induce voltage in coil placed in it. These voltage pulses can be processed and made available for measurement purpose . These voltage pulses from magnetic pick up are proportional to the rate of change of flux .Hence there is a certain minimum speed below which the induction will be weak to generate a pulse & hence a pulse could be missing here & there .This limit is below 5V motor voltage (from 3V to 5V), you may observe missed pulses there by causing erroneous reading of speed. Every time the tooth of wheel reaches over magnet it cut magnetic lines & hence induction of a voltage pulse. Hence, divide the frequency obtained at the output of sensor (tp 13) by 8 to get shaft rotation frequency. If a motor shaft fitted with ferrous slotted wheel it will cut magnetic field produced around a coil situated beneath the slotted wheel. Slotted wheel of magnetic material may alter magnetic field of magnetic pick up periodically on the uniform motion of motor. In this case voltage pulse from magnetic pick up if measured are found to be proportional to the motor speed (r. p. m).However, due to 8 slots ,it will produce 8 times pulses. Magnetic pick up used to measure Motor speed Panel circuitry consists of an emitter follower to drive motor .For speed variation a potentiometer is provided. Magnetic pick up gives output voltage in response to a rotating slotted wheel connected to the shaft of motor. This voltage is converted into pulses by a comparator. These pulses are converted into a DC voltage by frequency to voltage converter followed by an amplifier. Calibration requires zero adjustment for zero speed and span pot ,adjust for full speed Procedure Connect+_12v supply to the panel short the terminal as shown in wiring diagram by patch code for manual speed control of motor through potentiometer on panel . Select the magnetic pick up sensor by setting rotary 6 position switch at correct location [1st] as shown. Connect voltmeter to the output terminals to moniter the speed. Adjust zero pot for zero output voltage when moniter is stand still and adjust span potentiometer [ 2 v output voltage] when moniter is running at beyond 2000kpm speed. Repeat the procedure twice or thrice to confirm zero and full scale adjustment. Thus reading I n volt *2000 will display RPM measure frequency at tp 13 to confirm maximum speed of your moniter which will be beyond 2000 RPM. In case it is beyond 4000max then self span such that volt output x 2000 will be equal to RPM vary the speed of moniter by potentiometer. Note down the output voltage for each position of potentiometer. Measure voltage applied to the motor at the tag shown to the left hand lower corner of the wheel connected CRO to the left test point TP13(F) and observe the wave form for different motor speed. Motor speed measurement may be confirmed using external calibrated stroboscope or on board. Verify output voltage=[ f/8x16] 2000v so that even higher RPM you can observe the same on 0-2 range. This is very useful for computer intereferance Observation table :-