Rpm - tach readings vs multimeter vs Ear
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Fettling today, wanted to check the timing, but I can?t see the tach from outside the car so hooked up my multimeter. The differences were surprising:
Tach in car showed 6-700 revs
Multimeter showed 1500-1700 revs
My ear thought about 1100 revs.
I?ve always suspected the tach in the car to be a little low but not that much out. Has anyone else had strange readings from a multimeter ?
Nb car is stock, with points.
Regards
Richard
Tach in car showed 6-700 revs
Multimeter showed 1500-1700 revs
My ear thought about 1100 revs.
I?ve always suspected the tach in the car to be a little low but not that much out. Has anyone else had strange readings from a multimeter ?
Nb car is stock, with points.
Regards
Richard
Richard
'72 Sprint
'72 Sprint
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Bill it?s a Gunson -G4187; now discontinued.
Richard
'72 Sprint
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Hi Richard
that looks an interesting multimeter. I could not down load the book anywhere but as is only has probes I assume ( for +ve earth) that it is placed on the coil CB terminal +ve probe and earth -ve probe so with a standard coil ignition system that would be 2 pulses per rev for a 4 cylinder engine.
Just guessing here but could you check it on say an "old fashioned" battery charger ? this would give a rectified AC pulses at 100pps and 20V or so peak which would be 3000rpm as a guide that the meter is working ok.
but without the book can't be certain if it would work !
hope this helps
best of luck
Bob
that looks an interesting multimeter. I could not down load the book anywhere but as is only has probes I assume ( for +ve earth) that it is placed on the coil CB terminal +ve probe and earth -ve probe so with a standard coil ignition system that would be 2 pulses per rev for a 4 cylinder engine.
Just guessing here but could you check it on say an "old fashioned" battery charger ? this would give a rectified AC pulses at 100pps and 20V or so peak which would be 3000rpm as a guide that the meter is working ok.
but without the book can't be certain if it would work !
hope this helps
best of luck
Bob
- bob_rich
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My Fluke 87 has a frequency range on it, but I have not tried it.
I use a Tektronix THS720A digital oscilloscope with the low pass filter selected. It seems to work fine.
100 cycles/sec on the coil circuit is 3000 RPM.
Not usual garage kit I know, but I have it left over from retirement so I use that.
Eric in Burnley
1967 S3SE DHC
I use a Tektronix THS720A digital oscilloscope with the low pass filter selected. It seems to work fine.
100 cycles/sec on the coil circuit is 3000 RPM.
Not usual garage kit I know, but I have it left over from retirement so I use that.
Eric in Burnley
1967 S3SE DHC
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