Demise of the ammeter

Status
Not open for further replies.
motorson said:
You gave an example of when an amp meter would tell you more than a volt meter. (ie: Sulfated cell drawing more current) I believe I can know if the charging system is working by voltage because a 12v battery will drop to 12.5v with no alternator and I am seeing 13.6 while running. Also, I can know if I have a shorted or sulfated cell by the voltage after shut down. If I see less than 12.5 or whatever I am used to seeing with no alternator then I know something is wrong with the battery. I agreed with every thing you said in post #10. And, I have wished before that I could have both meters on a system. In my mind I think I can deduce more from a volt meter than I can from an amp meter though.
Click to expand...

This is certainly true for our Nortons, where the alternator cannot charge the battery at idle. That's why I have fitted a voltage monitor to my bike. As I said earlier, a voltmeter is an adequate monitor for systems with a permanent magnet alternator such as what we have.

If we were fortunate to have a real alternator which could supply all current once the engine was running, that'd be different. You'd get 14 volts regardless of battery condition and not know about the health of your battery until the next time you tried starting the motor. An ammeter would tell you of impending doom.

A BMW R1200 has an alternator as powerful as the one in my Oldsmobile. We could only wish.
 
Triton Thrasher said:
It doesn’t have to be a “positive earth ammeter.”
Click to expand...
When a designed for case grounding negative-ground ammeter is hooked up to a positive-ground system, it doesn't yeild the best result. I tried a Denso negative-case ground ammeter and it's in a box if you want to buy it and try it yourself. I suppose you could isolate it like old Triumph gauges, but I didn't want to go to all that trouble. The Jag-sourced unit works just fine.
 
Danno said:
When a designed for case grounding negative-ground ammeter is hooked up to a positive-ground system, it doesn't yeild the best result. I tried a Denso negative-case ground ammeter and it's in a box if you want to buy it and try it yourself. I suppose you could isolate it like old Triumph gauges, but I didn't want to go to all that trouble. The Jag-sourced unit works just fine.
Click to expand...

Earthed-case polarity-sensitive ammeters sound far removed from anything I’ve seen on a British bike.

I guess an earthed ammeter could work if you take the battery earth lead to the ammeter’s terminal, but the return side of the circuits would all have to go via the headlight shell, which seems a bit dodgy.

I’m open to be educated on what difference polarity makes to a centre-zero ammeter, apart from the “Charge” and “discharge” sides changing places. After all, it indicates current in both directions.
 
Triton Thrasher said:
I’m open to be educated on what difference polarity makes to a centre-zero ammeter, apart from the “Charge” and “discharge” sides changing places. After all, it indicates current in both directions.
Click to expand...

That's pretty much it. By convention, pointing positive means battery is charging.
 
Apologies for going off track a little but if you search eBay for “LED motorcycle bar charger” you’ll find handy dual USB chargers with LED voltmeter and temperature gauge built in. Waterproof and clips on and off the bike. Butt Ugly so only an option for the practical folk.
 
Davo said:
Apologies for going off track a little but if you search eBay for “LED motorcycle bar charger” you’ll find handy dual USB chargers with LED voltmeter and temperature gauge built in. Waterproof and clips on and off the bike. Butt Ugly so only an option for the practical folk.
Click to expand...

Even better is this. No longer do you need to worry if you can see the volts or the amps.

Voltmeter and Ammeter

Demise of the ammeter
 
I have the little LED volt meter which is rather useless out in direct sunlight. I wish it was more visible.
 
report back how well it works.... I mean,... electronics have progressed just a tiny bit since 1970, right?
 
I don't see a polarity sign on that ammeter display. An old Brit bike will go above and below zero depending on load and RPM.
 
I suppose not, as long as the meter won't be damaged by reverse polarity. For a single polarity meter I'd put it in the charge wire rather than the battery wire. That won't go reverse polarity.
 
Yes, because the purpose of an ammeter is to show current flow direction, not total amperage. When your bike is idling under the necessary RPM's required for the rotor/stator to supply enough amperage to power the components on your bike (headlight and running lights mostly) then your ammeter needle is in the negative direction showing that current is flowing out of your battery to power your components...

Once you hit the throttle and your RPM's rise, your ammeter needle goes strongly to positive until it restores the surface charge in your battery, then maintains a slight positive position as your zener diode dumps excessive charge and your rotor/stator continue to add it...

So, the ammeter's important information isn't total amperage. It's the direction of current flow...
 
I've found the Battery Status Monitor from Paul Goff more useful and much simpler to connect.
But sometimes missing the friendly waving of the ammeter.
 
Of course it does, because the ammeter shows direction of current flow. If the zener is dumping current, then current is flowing through the ammeter to it.... and the lights and whatever other components you turn on.
 
o0norton0o said:
Yes, because the purpose of an ammeter is to show current flow direction, not total amperage. When your bike is idling under the necessary RPM's required for the rotor/stator to supply enough amperage to power the components on your bike (headlight and running lights mostly) then your ammeter needle is in the negative direction showing that current is flowing out of your battery to power your components...

Once you hit the throttle and your RPM's rise, your ammeter needle goes strongly to positive until it restores the surface charge in your battery, then maintains a slight positive position as your zener diode dumps excessive charge and your rotor/stator continue to add it...

So, the ammeter's important information isn't total amperage. It's the direction of current flow...
Click to expand...

Right, so with this cheap one you assume 0 = negative direction. If increasing the amperage (increasing the revs) doesn’t bring you to the positive then you have a problem. It’s like a half an idiot light.
 
Status
Not open for further replies.

Similar threads

Chris T
  • Locked
how do I seal the ammeter in my headlamp?
Replies
4
Views
763
Tim_S
T
Back
Top