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1. Re: why optical sensors are use for measuring rpm?
DaKn_263916 Mar 29, 2013 6:31 AM (in response to userc_41987)1) Galvanic isolation.
2) Faster speed.
3) Larger distance between sensor and shaft depending on type.
www.ee.buffalo.edu/faculty/paololiu/566/sensors.ppt
Regards, Dana.
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2. Re: why optical sensors are use for measuring rpm?
JoMe_264151 Mar 29, 2013 8:10 AM (in response to userc_41987)... and can be used as a hand-held device to measure rotating parts without the need of an electrical connection.
Bob
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3. Re: why optical sensors are use for measuring rpm?
DaKn_263916 Mar 29, 2013 9:32 AM (in response to userc_41987)There are also number of transducer technologies that permit RPM
measurement, contactless, handheld, non optical, like -
1) Pressure
2) Sonic
3) Magnetic
etc..
Regards, Dana.
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4. Re: why optical sensors are use for measuring rpm?
userc_41987 Mar 30, 2013 11:07 AM (in response to userc_41987)how to get pulses from optical sensor?
tell me working principal?
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5. Re: why optical sensors are use for measuring rpm?
JoMe_264151 Mar 30, 2013 12:18 PM (in response to userc_41987)Imagine you have got an airplane modell and want to measure rpms of the propeller. The difference of light reflections can be the signal to count (and divide by two).
Or
a reflecting mark on a wheel could be detected. Usually you take a phototransistor or a photodiode for light detection. To further increase the insensitiveness against environment light you cold use an LED emitting at a higher frequency (kHz) and pick-up and filter your signal appropiately.
Bob
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6. Re: why optical sensors are use for measuring rpm?
DaKn_263916 Mar 30, 2013 2:17 PM (in response to userc_41987) -
7. Re: why optical sensors are use for measuring rpm?
DaKn_263916 Mar 30, 2013 2:32 PM (in response to userc_41987)Slotted disk approaches -
www.freemansgarage.com/tach.html
www.wisc-online.com/objects/viewobject.aspx
www.avagotech.com/pages/en/motion_control_encoder_products/
If shaft drives a generator/alternator, detect pole piece ripple frequency to compute RPM.
So may approaches, so little time.......
Regards, Dana.
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8. Re: why optical sensors are use for measuring rpm?
DaKn_263916 Mar 30, 2013 3:17 PM (in response to userc_41987)Dumb questions -
1) W what are you trying to measure the RPM of ?
2) Range of RPM you are trying to measure ?
3) Absolute accuracy you are trying to achive for measurment ? Or is relative accuracy more important ?
4) Environment the measurment is taking place in ? Temp, Pressure, Shock.......
5) Measurement device distance you desire from shaft that is rotating ?
6) Power available for measuring device ?
So many questions, so little time.........
Regards, Dana.