Lets Blow Up an Ammeter !
#21
Race Director
Thread Starter
#23
Race Director
Thread Starter
I thought it might surprise a few guys. I'm also wondering what can destroy a meter,I would think a short to ground would have to,but if it absorbs current and turns it into heat ,or light like a bulb maybe it won't blow. As I said I'm just a mechanic,but I do like to know how and why things work and break.
#24
Former Vendor
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St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
#27
Race Director
Thread Starter
Oh , I've already done that,post #25 in this thread.
http://forums.corvetteforum.com/c3-t...st-in-car.html
http://forums.corvetteforum.com/c3-t...st-in-car.html
#28
Melting Slicks
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St. Jude Donor '08
Oh , I've already done that,post #25 in this thread.
http://forums.corvetteforum.com/c3-t...st-in-car.html
http://forums.corvetteforum.com/c3-t...st-in-car.html
#29
Drifting
Very Roger. I have wired after-market ammeters into cars, with all the load except the starter going through the meter, no problem. But all the chatter on the forum had me thinking the stock Corvette meter would self destruct. Thanks for doing the test/demo!
Pete
Pete
#30
Race Director
Thread Starter
Thanks Pete I love doing this stuff.
Here are a few pics of the inside,if anyone was wondering.
1 1/2 volts pegs the needle,12v also pegs it but a little faster.
Here are a few pics of the inside,if anyone was wondering.
1 1/2 volts pegs the needle,12v also pegs it but a little faster.
#31
Team Owner
Definitely not stock ammeter guts, Roger...
#35
Drifting
An ammeter shows you right now what is happening, while a voltmeter is more of a long term indicator.
Pete
#36
Burning Brakes
#38
Melting Slicks
Myth Busted
Roger's experiment has effectively busted the myth that our ammeters are nothing more than millivolt meters.
The truth is that these are ammeters and there is current flowing through them. It is only a portion of the current flowing through the charging circuit so they must be calibrated to read the total amount of current. The ammeter circuit is in parallel with the main charging circuit and must carry current.
There is no way GM designed these ammeters to function as fuses for the rest of the ammeter circuit. If that was the case, there would be no need for the 20 gauge fusible links on each end of the circuit. Those fusible links serve as over load protection for the ammeter circuit. If the main wire in the charging circuit becomes open for some reason, the entire charging circuit current will try to flow through the ammeter circuit. At that point, something has got to give and it better not be the ammeter.
I said in the other thread that Roger's results were not surprising to me. My guess is that these ammeters are designed to handle at a minimum the same amount of current as the 16 gauge wires and 20 gauge fusible links in the rest of the circuit are designed to handle. Probably more as no capable engineer would ever design an ammeter to function as protection for wires and fusible links. Roger's ammeter is certainly quite capable of carrying significant amounts of current compared to what was previously thought possible.
If anyone wants to take this further, just find a "real" ammeter and wire it in series in the ammeter circuit to monitor the current that flows given various charging conditions.
Thanks Roger.
DC
The truth is that these are ammeters and there is current flowing through them. It is only a portion of the current flowing through the charging circuit so they must be calibrated to read the total amount of current. The ammeter circuit is in parallel with the main charging circuit and must carry current.
There is no way GM designed these ammeters to function as fuses for the rest of the ammeter circuit. If that was the case, there would be no need for the 20 gauge fusible links on each end of the circuit. Those fusible links serve as over load protection for the ammeter circuit. If the main wire in the charging circuit becomes open for some reason, the entire charging circuit current will try to flow through the ammeter circuit. At that point, something has got to give and it better not be the ammeter.
I said in the other thread that Roger's results were not surprising to me. My guess is that these ammeters are designed to handle at a minimum the same amount of current as the 16 gauge wires and 20 gauge fusible links in the rest of the circuit are designed to handle. Probably more as no capable engineer would ever design an ammeter to function as protection for wires and fusible links. Roger's ammeter is certainly quite capable of carrying significant amounts of current compared to what was previously thought possible.
If anyone wants to take this further, just find a "real" ammeter and wire it in series in the ammeter circuit to monitor the current that flows given various charging conditions.
Thanks Roger.
DC
#39
Team Owner
OK. Have any of you traced out to see where the leads from the ammeter actually go? No? Well, that might be an "issue" with your "current through the ammeter" theory. One lead runs to one end of that 20 awg fusible link...the other end of which is connected to a main power line (10 awg red). The other lead runs to the horn relay which, by the way, is directly connected to that same red 10 awg main power line--but downstream a ways. So, the two leads are electrically connected to the same wire which does not have any other devices between those two points!! How can that be? Well, because that length of wire between them is the shunt circuit for the ammeter.
You think current flows through the ammeter, even though the two ends of the ammeter leads are electrically connected together...except for the few feet of 10 awg wire and its [very small] resistance? OK. And the world is flat for some folks, too. Believe what you will.
You think current flows through the ammeter, even though the two ends of the ammeter leads are electrically connected together...except for the few feet of 10 awg wire and its [very small] resistance? OK. And the world is flat for some folks, too. Believe what you will.