Positive earth ammeter

[Tom H]

A fellow Alpine owner asked me about how an ammeter should be wired in a SII. I assume it's still a Pos earth car. Some ( non Alpine) ammeters I have seen are labelled with Charge and Discharge so it's pretty clear that they would be wired such that when the generator is charging the battery the needle would be in the Charge side of zero, regardless of earth polarity. But all Alpine ammeters I have seen are labeled with + and -. I know on my Neg earth SV, when charging, the ammeter needle should be in the + side. But in a Pos earth car like an SI thru SIV, I can see logical reasons for either + or - indication when charging. Does anyone here know what is the common convention in a Pos earth car? Does it indicate + or - when charging?

Tom H

 

[RootesRacer]

Charge is charge regardless of polarity (as is discharge).

+ indicates charge and - indicates discharge.


Good thought though.

 

[Tom H]

In a Pos earth car charging is actually "-" current.

In spite of that, I am 90% in agreement that even in a pos earth car, charging would be indicated as + , but I am hoping to get confirmation of that from someone who has a Pos earth car.

Tom

 

[beamdream]

In a Pos earth car charging is actually "-" current.

In spite of that, I am 90% in agreement that even in a pos earth car, charging would be indicated as + , but I am hoping to get confirmation of that from someone who has a Pos earth car.

Tom

Perhaps you might consider the repolarising of the generator when you change a positive earth system to negative; if you don't switch the ammeter wires the meter will work in reverse, and yes I have vehicles with both systems, they both read + when charging and - when discharging.

 

[Series3Scott]

While driving my positive Series 3 yesterday the ammeter needle was on the "+" side, charging the battery.

 

[65beam]

positive

my series 4 has a lucas amp guage that reads positive on the left side, negative to the right. before I switched to negative ground it always showed the needle on the + side when charging. the Harrington does have the original amp guage and reads to the + side when charging. I switched the wires when I converted both cars to negative ground.

 

[Tom H]

OK, it's settled then. So Charging is indicated by "+" regardless of whether it's Pos or Neg earth.

Thanks guys.

Tom

 

[65beam]

positive

tom,
look on the positive side. anything good that happens is a positive. not recharging the battery is a negative but charging is a positive.

 

[Tom H]

65beam said:

look on the positive side. anything good that happens is a positive. not recharging the battery is a negative but charging is a positive.

Hey, I'm positive that's a very logical way to view it. And I love the play on words: "look at the positive side". That's a great motto I try to live by, even when speaking of positive or negative voltage and current.

Tom