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May 25, 2015, 08:47:14 AM

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Author Topic: Amp meter  (Read 109 times)

solg

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Amp meter
« on: May 17, 2015, 07:20:05 PM »
I've noticed that while using points,when going thru my kickstart routine,the piston gets to TDC and the amp meter deflects to neg. then pushing the kick starter a little further( the ideal point for me to kickstart From) the meter returns to normal. Now, when using an electronic ignition unit the amp meter doesn't move at all. Anyone know why this is?
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Arizoni

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Re: Amp meter
« Reply #1 on: May 17, 2015, 08:17:14 PM »
Your description makes me wonder if your amp-meter is hooked up backwards.
That really doesn't matter because it can work in both directions just fine.

Anyway, with the old style ignition points, they are normally closed.

In the closed position the electrical power from the battery passes thru them to energize the ignition coil.  This should make the amp-meter read negative  (-).
  This is all happening while the engine is going thru the power, exhaust, inlet and the first part of the compression strokes.

When the crankshaft is just about to reach top dead center on the compression stroke the ignition cam causes the ignition points to open which stops the power flow from the battery.
With the battery no longer supplying power to the ignition coil the amp-meter should return to zero.  This is the movement you see on the amp-meter and it is a good indicator that the piston is at (or near) TDC and ready to be kicked to life with the kick starter.

Without the supply of electrical power, the magnetic field that the ignition coil created when it was getting electrical power, collapses and disappears.

The sudden collapse of the magnetic field causes a massive amount of voltage to be created in the ignition coils "secondary windings".  This high voltage escapes thru the spark plug wire and causes the spark on the tip of the spark plug.

The electronic ignition system works a bit differently.

Usually, the electrical power is not sent to the ignition coil until it is time for the spark to occur so there is no steady state discharge indicated on the amp-meter.  That's why the amp-meter needle doesn't move when the ignition switch is turned on.

When the small magnet on the rotating ignition shaft passes the electronic ignition's sensor, the EI computer sends the battery power to the coil creating the magnetic field and then shuts if off.  This creates the power in the coil needed to produce the spark.
 While the battery power being supplied to the ignition coil is rather large,  the "on/off"  happens so fast that the amp-meter can't react to it so the needle doesn't noticeably move.

Another reason the needle doesn't move goes back to that magnet on the rotating ignition shaft.

If the magnet approaches the sensor slowly (like when your slowly kicking the engine over with the kick starter), the sensor won't notice the change in the magnetic field.
If the sensor doesn't notice the change in the magnetic field, it won't turn on the power to the coil so the needle doesn't move.

At least this is my version of what is happening in there.
Now, the experts can tell you what's really happening.  ;D ;D


« Last Edit: May 17, 2015, 08:23:19 PM by Arizoni »
Jim
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Re: Amp meter
« Reply #2 on: May 18, 2015, 06:47:26 PM »
Loved your explanation Arizoni.

solg

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Re: Amp meter
« Reply #3 on: May 18, 2015, 07:03:19 PM »
Thanks AZ. I  have a power arc, no magnets, but, I get the point . That  made  sense. I may not have explained things correctly but,that is what is happening.
 As a side note. I'm amazed at how fast things are happening in the world of those electrons!
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