Petronix

dwag · May 9, 2023

Put Petronix ign & self exiting/1 wire delco alt on Massey 35. Check charging w/digital voltmeter and get erratic reading/voltage but my old needle voltmeter shows 14v and steady. Suppose it's the copper core plug wires causing this?

Janicholson · May 9, 2023

digital meters sample voltage maybe every 20 milliseconds (it varies). Old tractors and cars have few signal smoothing components (filters) The analog meter averages the information it presents. The digital shows the instantaneous voltage it sees at that sample. I have a $200.00 Fluke digital that reads correctly because it processes the noisy voltage into a stable reading. Generally a needle type gauge will present the information better. I use both, but don't use the expensive meter in the field. Your analog meter is correct. Jim

used red MN · May 9, 2023

Unless things have changed I believe Petronix probably has a warning somewhere in the literature you received warning you that the use of copper core plug wires with their electronic ignitions is not recommended. Obviously it will run with them. I believe they say the RF noise can be detrimental to the electronics in their units. You are likely correct that the ignition is messing with the reading on your digital meter. Is it a cheap one? Run whatever plug wires you want, but I would recommend double checking all your connections for tightness especially grounds.

Dingo3 · May 9, 2023

^x2
Dont know if that is your problem with the reading but its a good place to start.

55 50 Ron · May 9, 2023

Yep. I have a Fluke also and it reads steady voltage also, but I haven't had it near a Pertronix ignition.

JMOR · May 9, 2023

(quoted from post at 14:07:33 05/09/23) Put Petronix ign & self exiting/1 wire delco alt on Massey 35. Check charging w/digital voltmeter and get erratic reading/voltage but my old needle voltmeter shows 14v and steady. Suppose it's the copper core plug wires causing this?

our alternator output is [u:edbf688277]not[/u:edbf688277] a steady DC voltage....it looks like this:

MarkB_MI · May 10, 2023

Those copper core plug wires can lead to premature Pertronix failure. Replace them with resistance wires.

Where are you measuring the voltage? Regardless of noise, it should be consistent at the battery. And any decent digital multimeter should filter out noise. Most quality DMMs use a technique called '<a href=https://en.wikipedia.org/wiki/Integrating_ADC>dual-slope integration</a>' that has high immunity to noise. But a cheap DMM may use a different technique that offers less noise immunity.

dwag · May 10, 2023

Still kinda puzzled why my Snan On battery tester/elec diagnoser & my Fluke meter work OK on other vehicles?

Petronix

dwag

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Janicholson

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used red MN

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Dingo3

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55 50 Ron

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JMOR

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MarkB_MI

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dwag

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