How to use digital multi meter for rpms
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- Rusty Probie
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How to use digital multi meter for rpms
Where do you connect the multi meter to measure rpms
- desertrefugee
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Re: How to use digital multi meter for rpms
Cant get there with a DMM. An oscilloscope is needed. You need to measure pulses.
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Re: How to use digital multi meter for rpms
hmm, really?
I never knew this.
Thanks!
I never knew this.
Thanks!
sorta bulldogged custom 1978 GL1000 - "geekster"
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full Vetter dress 1979 GL1000 - "Barge" (currently down)
1986 1200 Aspencade - "Heart of Gold" - daily rider
1990 1500 Aspencade - It's ALIVE! but very, very naked. not in a good way.
1978 for $100 - project in worx
1978 from a previous member here - taking up space
my original '79 bought in '91 - replacing engine (eventually, maybe someday)
H2G2=42
A competent and self-confident person is incapable of jealousy in anything. Jealousy is invariably a symptom of neurotic insecurity. ~ Robert A. Heinlein
The good thing about science is that it's true whether or not you believe in it. ~ Neil deGrasse Tyson
- flyin900
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Re: How to use digital multi meter for rpms
Don’t believe that is correct as my DMM has a section for RPM on a variety of multi cylinder engines. Don’t ask me how to use it though, as I have never hooked it up for that purpose and don’t have the instruction anymore.
Current Bikes:
1966 CL77 - Honda 305cc - Dual purpose - "Gentleman's Scrambler" was a period moniker.
1967 CL175K0 - Low production number with #802 engine serial- winter 2019/2020 full restoration.
1972 CB350F - Baby Four with low mileage - Cosmetic refresh to the next level 2021/2022.
1978 CB550K - Very original bike with only 7499 Km. from new - light cleanup and refresh done.
1983 CB1100F - Canadian model - DOHC Supersport in pristine low kilometre condition from new.
1984 GL1200 - Standard model in showroom condition - two owner bike from new.
1984 CX650E - Restored summer 2017 - a rare Eurosport model - excellent one owner bike.
1966 CL77 - Honda 305cc - Dual purpose - "Gentleman's Scrambler" was a period moniker.
1967 CL175K0 - Low production number with #802 engine serial- winter 2019/2020 full restoration.
1972 CB350F - Baby Four with low mileage - Cosmetic refresh to the next level 2021/2022.
1978 CB550K - Very original bike with only 7499 Km. from new - light cleanup and refresh done.
1983 CB1100F - Canadian model - DOHC Supersport in pristine low kilometre condition from new.
1984 GL1200 - Standard model in showroom condition - two owner bike from new.
1984 CX650E - Restored summer 2017 - a rare Eurosport model - excellent one owner bike.
- pidjones
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Re: How to use digital multi meter for rpms
So, not just any DMM, but rather one that has the tach function.
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1978 GL1000 with '75 engine - the Hunley
Ex 1978 GL1000
Ex 1979 GL1000
Ex '79 CB750F rat bike
Ex '86 SEi
Ex '77 GL1000
Ex '76 RD400
Ex '72 Penton 125 set up for flat track
Ex '73 RD250
Ex '68 TR6C - chopped
Ex 2006 GL1800 - the Black Pearl SOLD! to make room for:
2021 Can-Am Spyder RT Limited Dark Chalk Metallic
1975 Red GL1000 project - ex Pistol Pete project
1972 Triumph T150V Trident rescue - finished and FOR SALE!
1976 Yamaha RD400c
1978 GL1000 with '75 engine - the Hunley
Ex 1978 GL1000
Ex 1979 GL1000
Ex '79 CB750F rat bike
Ex '86 SEi
Ex '77 GL1000
Ex '76 RD400
Ex '72 Penton 125 set up for flat track
Ex '73 RD250
Ex '68 TR6C - chopped
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Re: How to use digital multi meter for rpms
A very specialized tool, that. I've never seen one, and I used to use electronic test equipment professionally.
- Whiskerfish
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Re: How to use digital multi meter for rpms
Several of the Fluke DMM's have a RMS function that can be used for this.
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"The book is wrong, this whole Conclusion is Fallacious" River Tam
2008 GL1800 IIIA "TH3DOG"
1975/6/7/8/9 Arthur Fulmer Dressed Road bike
1975 Naked Noisy and Nasty in town bike
and a whole garage full of possibilities!!
Psst. oh and by the way CHANGE YOUR BELTS!!!!
- desertrefugee
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Re: How to use digital multi meter for rpms
RMS function won’t get you there. As noted, you’ll need the specialized instruments which can be expensive have to be configured to measure ignition pulses going to the coil. RMS simply gives you another way of looking at AC power other than peak to peak.
Since those aren’t typical DMMs, I did not consider them in the discussion.
Since those aren’t typical DMMs, I did not consider them in the discussion.
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- Whiskerfish
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Re: How to use digital multi meter for rpms
All you do is take the rms and multiply by 60. Then correct it for the wasted spark.
"Agreement is not a requirement for Respect" CDR Michael Smith USN (Ret) 2017
"The book is wrong, this whole Conclusion is Fallacious" River Tam
2008 GL1800 IIIA "TH3DOG"
1975/6/7/8/9 Arthur Fulmer Dressed Road bike
1975 Naked Noisy and Nasty in town bike
and a whole garage full of possibilities!!
Psst. oh and by the way CHANGE YOUR BELTS!!!!
"The book is wrong, this whole Conclusion is Fallacious" River Tam
2008 GL1800 IIIA "TH3DOG"
1975/6/7/8/9 Arthur Fulmer Dressed Road bike
1975 Naked Noisy and Nasty in town bike
and a whole garage full of possibilities!!
Psst. oh and by the way CHANGE YOUR BELTS!!!!
- flyin900
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Re: How to use digital multi meter for rpms
Here's the one I have, yet only use it for electrical/impedance stuff. Should try to find the instructions and see how this other stuff works.
Current Bikes:
1966 CL77 - Honda 305cc - Dual purpose - "Gentleman's Scrambler" was a period moniker.
1967 CL175K0 - Low production number with #802 engine serial- winter 2019/2020 full restoration.
1972 CB350F - Baby Four with low mileage - Cosmetic refresh to the next level 2021/2022.
1978 CB550K - Very original bike with only 7499 Km. from new - light cleanup and refresh done.
1983 CB1100F - Canadian model - DOHC Supersport in pristine low kilometre condition from new.
1984 GL1200 - Standard model in showroom condition - two owner bike from new.
1984 CX650E - Restored summer 2017 - a rare Eurosport model - excellent one owner bike.
1966 CL77 - Honda 305cc - Dual purpose - "Gentleman's Scrambler" was a period moniker.
1967 CL175K0 - Low production number with #802 engine serial- winter 2019/2020 full restoration.
1972 CB350F - Baby Four with low mileage - Cosmetic refresh to the next level 2021/2022.
1978 CB550K - Very original bike with only 7499 Km. from new - light cleanup and refresh done.
1983 CB1100F - Canadian model - DOHC Supersport in pristine low kilometre condition from new.
1984 GL1200 - Standard model in showroom condition - two owner bike from new.
1984 CX650E - Restored summer 2017 - a rare Eurosport model - excellent one owner bike.
- desertrefugee
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Re: How to use digital multi meter for rpms
Hmm. That works? I'll be danged. I guess its using the RMS function to measure the pulse frequency and then mutiply to get one minute. If youre only looking at one coil, maybe the wasted spark correction isnt needed?Whiskerfish wrote:All you do is take the rms and multiply by 60. Then correct it for the wasted spark.
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- mikenixon
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Re: How to use digital multi meter for rpms
As I recall, Fluke sells an rpm attachment for their digital multimeters. Never tried it though. Most shops use standalone rpm test tools. Used a lot on ATVs and other vehicles to set idle speed carefully so as to be compatible with CVT (automatic transmission) systems.
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Re: How to use digital multi meter for rpms
In electronics RMS stands for Root Mean Square and is the DC equivalent of an AC wave. Nothing to do with frequency.
- desertrefugee
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Re: How to use digital multi meter for rpms
This got my interest up. Poked around a bit. You can calculate frequency using a true RMS meter. Since most alternating current sources are not a clean, pure sine wave, straight RMS calculations will not work. Or at least would not be very accurate. That’s why true RMS methods are used. Also, the sample window must be short and defined or the frame needs to be short enough so that voltage changes cannot corrupt the calculation - a constant, stable peak to peak amplitude is essential.
I suspect that the generic DMM versions of "tachs" are adequate, but not entirely accurate. I could be wrong, but if you're looking for precision, a dedicated instrument would be the route to take.
I spent some time (decades) in an engineering lab, but mostly slinging code.
I suspect that the generic DMM versions of "tachs" are adequate, but not entirely accurate. I could be wrong, but if you're looking for precision, a dedicated instrument would be the route to take.
I spent some time (decades) in an engineering lab, but mostly slinging code.
Last edited by desertrefugee on Sat Jul 27, 2019 5:43 pm, edited 1 time in total.
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Re: How to use digital multi meter for rpms
My fluke 78 has functions for rpm and dwell but it was built for the auto repair industry. To use the rpm it has an inductive clamp that goes around a plug wire. Some timing light have rpm functions as well.
To use a Dmm it would have to be able to have graphing features so you could see the waveform. Seems in this day and age there must be a cheap inductive tach out there.
To use a Dmm it would have to be able to have graphing features so you could see the waveform. Seems in this day and age there must be a cheap inductive tach out there.
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