Revolution Counter / Tachometer

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SEABEE Associate Join Date: Jan 2008 Posts: 30	Revolution Counter / Tachometer 02/11/2008 12:06 AM
	Hello CR4 Forum, I seek to build a diesel injection pump test stand. The stand will turn the injection pump at a pre selected speed. However it is necessary to record and display the number of revolutions as well as the speed in revolutions per minute. The machine must be able to indicate cc's per 1000 strokes (of the pumping element). My request for information regards the type of instrumentation necessary to do this counting and hopefully tachometer functions also. Instrumentation which can be set to open a relay at a certain number of revolutions would be optimal. Pump delivery (fluid volume) can easily be accomplished manually. Thanks in advance for any thoughts or suggestions. Dan
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Anonymous Poster	#1 Re: Revolution counter/Tachometer 02/11/2008 12:36 AM
	Sounds like you need a crank position sensor - basically a Hall Effect switch that is triggered by a tone-wheel mounted to the shaft. All you need then is some software to record the pulses and count revolutions and calculate RPM's.
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Electroman Guru Join Date: Jul 2006 Location: Dunstable, England Posts: 2821 Good Answers: 45	#2 Re: Revolution counter/Tachometer 02/11/2008 8:43 AM
	So you just need an revolution per minute indicator and a totalising counter then - That's a bit easy isn't it? You can buy a rpm meter with a totalising function for a few tens of Quid, dollars etc... Just attach the sticky reflective tape to the shaft and point the meter at it and read the display. John. __________________ A little knowledge is a dangerous thing - Googling is far worse!
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SEABEE Associate Join Date: Jan 2008 Posts: 30	#3 In reply to #2 Re: Revolution counter/Tachometer 02/11/2008 10:13 AM
	Thanks for the reply. So far my search for such a device has failed. I see a variety of counters and RPM checkers, mainly for the bicycling application. Can you suggest a source? Thanks, Dan
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Electroman Guru Join Date: Jul 2006 Location: Dunstable, England Posts: 2821 Good Answers: 45	#4 In reply to #3 Re: Revolution counter/Tachometer 02/11/2008 11:18 AM
	I found loads on ebay, mostly they are the tacho variety but some do have the totaliser function on them.... http://cgi.ebay.co.uk/TACHOMETER-DIGITAL-LASER-RPM-REV-TESTER-METER-CAR-LCD_W0QQitemZ330210686874QQihZ014QQcategoryZ4678QQssPageNameZWDVWQQrdZ1QQcmdZViewItem There are ooodles of others from all over the world on ebay.com as well... John. __________________ A little knowledge is a dangerous thing - Googling is far worse!
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Andy Germany Guru Join Date: Sep 2006 Location: Near Frankfurt am Main, Germany. 50.390866N, 8.884827E Posts: 17996 Good Answers: 200	#5 Re: Revolution Counter / Tachometer 02/12/2008 4:54 AM
	A better method and less dangerous than reading a marker on a turning part of the engine is to use a simple senor to not the pulses of fuel going through just one of the supply lines to the diesel injector. (this would also work on a petrol injected engine if needed.... That is how the equipment used in car workshops is made and is connected using a simple clip, similar to a clothes peg. The sensor can be one of those cheap Piezo sounders working in reverse.....they give an outstandingly high voltage out under such conditions. A sensitivity control is needed to get the sensor working on just the sound of the one pipe...then square and clean the signal up and apply it to a frequency counter!! Multiply the reading by 2 to get the actual RPM of any 4 stroke engine. Job done! __________________ "What others say about you reveals more about them, than it does you." Anon.
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JohnBob Associate Join Date: Jan 2008 Location: Bath, UK Posts: 53 Good Answers: 2	#6 In reply to #5 Re: Revolution Counter / Tachometer 02/12/2008 5:19 AM
	Yea Andy is right, the way many injection pump calibration units work is a sensor on the injector line / pipe. This way one can count the pulses (therefor revolutions) and get the timing, all from the one sensor.
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logix101 Power-User Join Date: Jan 2008 Posts: 203 Good Answers: 2	#7 Re: Revolution Counter / Tachometer 02/12/2008 8:13 AM
	Check with omega.com they have counters and loggers. and they are traceable this will help with the validation of your process. __________________ The more complex the mind, the greater the need for the simplicity of play... If you think you can or think you can't you'll always be right
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Andy Germany (1); Anonymous Poster (1); Electroman (2); JohnBob (1); logix101 (1); SEABEE (1)

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