amp meter or volt meter

[forrest]

how would one replace an amp meter with a volt meter. Id rather know what my voltage is at the battery than to know what I'm drawing or charging.

[Original50]

That would be a mistake since you would ALWAYS read the battery source voltage when the car isn't running and with it running it would read higher than the battery voltage from the generator/alternator providing the voltage level that would be read. The source voltage includes the internal resistance of the battery, and if it is a 6 volt battery the voltmeter would read 6 volts regardless if one of the cells are dead. It would give you the feeling that if it read 6 volts, then the battery is good, which is not the way it goes in the electronic world. You need to understand electrical theory to get the jest of reading voltage with a meter.
With an amp meter you get the characteristics of what is occuring with the current draw that is occuring with the car's electrical system. The regulator is the instrument that makes sure the system works correctly as the regulator should provide a charge to the battery when the battery tells the regulator to give it more juice via the points in the regulator.

Don Dodson

[GTtim]

Forest, I think you are correct in thinking that the voltmeter is a better meter to have than an ammeter. No modern cars that I know of use an ammeter any more. Probably the single biggest reason is that you don't have to have some monster high load cable running behind your dash with connections to the meter that can corrode and induce resistance and cause fires. As for how you would wire it, I don't know the specifics. I hope this thread continues with some suggestions. I bet if you bought a new voltmeter it would show you how to wire it. Maybe Biggs will give us an enlightened opinion, as he has electrics in his professional background.

Tim K.
'64 R2 GT Hawk

[64V-K7]

Ammeters measure the amount of current flow (charge/discharge). They are wired, such, that the current doesn't pass thru the meter exactly. The needle and guaging mechanism are separate from the actual current carrying wire. The poles on the meter are (+) battery side) and (-) buss side and just run through the gauge. While the current passes from (+) to (-), the small coil, with the needle attached, measures (senses) the direction and amount of current, known as the field. The sensing coil is sized to the original circuit, so if you increase the output of the generator/alternator, you can peg the needle easily. This won't hurt anything right away, but you can burn out the coil eventually

The voltmeters measure the amount of voltage (electrical pressure) in the circuit. They are wired just like any other gauge. The (+) is a tap to the power side and the (-) is grounded.

In actuality, they both give vital information. If you only have a voltmeter and your generator stops charging, you won't know about it right away, but the ammeter would give a discharge indication...
If the generator or voltage regulator malfunctioned, the ammeter would still show a charge, but the voltmeter would show less voltage as you ran along.

[Swifster]

quote:Originally posted by GTtim

Forest, I think you are correct in thinking that the voltmeter is a better meter to have than an ammeter. No modern cars that I know of use an ammeter any more. Probably the single biggest reason is that you don't have to have some monster high load cable running behind your dash with connections to the meter that can corrode and induce resistance and cause fires. As for how you would wire it, I don't know the specifics. I hope this thread continues with some suggestions. I bet if you bought a new voltmeter it would show you how to wire it. Maybe Biggs will give us an enlightened opinion, as he has electrics in his professional background.

Tim K.
'64 R2 GT Hawk

The reason volt meters are in use today vs an ammeter is that aternators/generators of the time were 60 amps max. Today they are 130+ amps. You are correct about the size cable needed to hold that much current. Using a 30-45 amp alternator such as came on the car doesn't require the same size cable.

Both will give information, but one is safe at low amperage and the other is safe at any amperage. Because I'll be using a 130 alternator in the Daytona, I'll be using a volt meter. Personally, I think an ammeter provides more information.

---------------------------------------------------------------------------------------------------
Tom - Lakeland, FL

1964 Studebaker Daytona



Michigan Speed - www.michiganspeed.com
Club Hot Rod - www.clubhotrod.com
LS1 Tech - www.ls1tech.com

[John Kirchhoff]

I have things (cars, tractors) with either of the two meters and the main difference between the two is that a volt meter is more indicitive of whether the charging system and regulator in particular is workin while the ammeter is a better gauge of the state of charge of the battery. A volt meter can say 14.5 volts but you have no idea if the alternator is producing 2 or 20 amps and the battery is full charge or half charge. In actuality, full tilt charge will usually pull the voltage down a volt or so because of the increased amperage load. From the other point of view, you could have a shorted out field coil, be low on voltage but still show a positive charge. One thing an ammeter will clue you in on that a volt meter won't is if you have a battery going south. One about to die or with a dead cell will never charge completely and therefore the ammeter is going to show an inordinatly high amperage (charging) reading continually.

Here's the best way to explain the difference between voltage and amperage. Think of voltage as a flowing river and amperage as a tug boat on that river. A flowing river (positive voltage) without a boat on is does no work. Boats (amperage) do work but they can't work if the river's too low, so a certain amount of current flowing is needed to get work done.

[rons50]

An ammeter is connected in series (in line) with the current it is measuring. A voltmeter is connected in parallel (across) the potential it is measuring. An ammeter will measure the amount of current (electrons) that is flowing through a circuit, a voltmeter measures how much force (volts) is pushing the current through a resistance (the circuit). BTW, an ohmmeter measures the resistance.

Ron

[Swifster]

ANYWAYS, to answer your question of how, you'd have to have a guage made. As far as I know, Studebaker never used a volt meter (of course I could be wrong ). You can send the guage cluster to Classic Instruments and they can convert the guage over to volts. This may not be cheap, but their stuff is excellent.

Classic Instruments = http://www.classicinstruments.com

---------------------------------------------------------------------------------------------------
Tom - Lakeland, FL

1964 Studebaker Daytona



Michigan Speed - www.michiganspeed.com
Club Hot Rod - www.clubhotrod.com
LS1 Tech - www.ls1tech.com

[JDP]

here's a good answer:

"Which is better for monitoring a vehicle's electrical system - a Voltmeter or an Ammeter?

Short answer:
A voltmeter, by far.

Electrical guru Mark Hamilton of M.A.D. Enterprises points out that amperage is a measure of current flow, so an ammeter is actually a "flow meter" that's intended to measure current flow to the battery (under normal conditions) or discharge from the battery (in the case of alternator system failure). On a typical flow meter, all output must be directed through the device to obtain an accurate reading. In the ammeter's case, that means all the alternator output used to recharge the battery must first be routed through the ammeter under the dash. Which requires a heavy-gauge cable and presents a possible fire hazard. And the ammeter itself must be able to handle all this current flow, so it must have a higher current rating than the alternator's maximum rated output.

All this might be worth the hassle if the ammeter produced reliable information. But the ammeter can only measure the amount of current output to the battery for recharging purposes: When the alternator recharges a "low" battery, the ammeter indicates a high charge rate; with a fully charged battery the voltage regulator reduces alternator output, and the ammeter is supposed to indicate a very low charge rate. But how can you really tell the regulator has reduced alternator output because the battery is fully charged? Maybe a diode in the alternator rectifier failed, or the alternator belt slipped after it warmed up, just as if the battery were fully charged. Or maybe the meter indicates a medium charge rate most of the time-does the battery want this much or could the voltage regulator be overcharging the battery?

On the other hand, a voltmeter works like a fuel pressure gauge-but instead of measuring fluid in psi, the voltmeter measures electrical system pressure in volts. Just like a fuel pressure gauge, a voltmeter only needs to tap into a circuit; all the fuel (or electricity) does not have to detour through the gauge itself. Voltmeter installation is easy, quick, and safe: It hooks up to a fused, ignition-switched "off/on" source and does not require any modification of the circuit used to recharge the battery or any part of the alternator/regulator system. In short, the voltmeter installed at the dash will be a stand-alone circuit.

The voltmeter directly measures the result of charging-system performance. With normal alternator/voltage-regulator function, battery voltage is maintained at 14.0 to 14.5 volts-and this is reported directly by the voltmeter. In the event of alternator-system failure, voltage will be low and continue to drop as the battery discharges. In the event of an "overcharge" condition, the voltmeter will climb above its normal zone. In summary, there is no chance for misinterpreting a voltmeter's readings as can happen with an ammeter."


JDP
Arnold Md.
Studebaker On The Net

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[CHAMP]

If they both have advantages and disadvantages why not have both[?]

GARY H 2DR.SEDAN 48 STUDEBAKER CHAMPION NORTHEAST MD.

[John Kirchhoff]

And if you think about it, a lot of Larks had neither, just a light that only lit up when no charging was being done.

But I guess to answer Forrest's question, Stweart Warner still makes voltmeters that look almost exactly like what a Hawk would have. If you want to replace the ammeter with the volt meter, consider getting a large diameter piece of shrink tubing, disconnect the ammeter and with a small bolt, connect the two terminals, slip the shrink tubing over the connection, heat it up and to be safe, cut a piece of rubber hose and slip over the connection. Wire the + side of the voltmeter to the ignition terminal and ground the - and you're set to go.

Actually you can connect the + terminal to any hot wire you want at any point. The difference is that if you connect it "downstream" of any loads (lights, heater, etc) the voltage is going to read lower. A sensitive voltmeter that's not dampened suffeciently will have a tendency to bounce on a system with a mechanical voltage regulator as the points open and close. Locating the tap downstream of a constant, sizable load will help dampen needle movement. If you really want to nit pick, the reading off the ignition terminal is going to be incorrect because of the internal resistance of the wire leading from the battery to the terminal or when charging, in the wire from the alternator/generator to the terminal and any loads that may be in between. So a voltmeter isn't 100% accurate either and is realitive to your vehicle, tap location and the load at the time. Don't anyone take offense, that's not me talking, that's Ohm's Law and Kirchhoff's Law (sorry, that's Gustav, not John).

[Original50]

quote:Originally posted by CHAMP

If they both have advantages and disadvantages why not have both[?]

GARY H 2DR.SEDAN 48 STUDEBAKER CHAMPION NORTHEAST MD.

Gary, that is a good point and I know there are some responses coming from some of the members that indicates some question marks are prevalant. I failed do indicate in my first response that I am an Electronics Technician for the past 44 years, and that I do know a thing or two about the electrical systems on our cars. It can become very frustrating for the layman to try to understand some of the in- depth details of electronic jargin that can be thrown at them from the haystack, so I won't get involved with that part of the equation.
I am wondering why Forrest wants to measure voltage instead of looking at the entire system as it was designed by the engineers at Studebaker, but evidently he has his reasons, and it has sparked an interest by other readers of this thread.
If the voltage is measured at the battery, then it needs to be taken into consideration what does he want to read exactly? He has to have a load on the battery to get a correct reading of the battery voltage, such a radio turned on, headlights on, or cigarette lighter pushed in, and the measurement would then reflect the true actual voltage available from the battery. There is something that occurs with every battery out there, and that is the internal resistance of the battery, which includes the natural checmical reaction that occurs within the battery. That internal resistance actually reduces the amount of voltage that is actually available to the output of the battery. A Dead Cell is considered to be internal resistance, and on a 6 volt battery, a dead cell would subtract 2 volts from the available battery, but if you measured the battery voltage it would show 6 volts without a load on the battery. Under the same scenerio, if you had a dead cell and used an ammeter, the ammeter would show an abnormal charge rate with the engine reved up, as the generator would be trying to charge that dead cell, to no avail, and the lights and other applainces would NOT be getting the voltage required to operate them properly. Of course the generator or alternator would be providing a larger voltage output to charge the battery. I don't know what that voltage is on a 6 volt car(proberly around 7 volts), but for a 12 volts system it is between 14.4 to 14.7 volts. Using these values, if you have an ammeter and a voltmeter monitoring your system, and you read 14.7 volts with the engine running, and your ammeter showed a plus level of charge, then you would expect your battery to be charging. If you turned off your ignition, and then tried to start you car only to get the solonoid clicking, then it would be apparant that the battery is failing to charge, or that there is one heck of a short somewhere. To make the story a little more understanding, it would be helpful to understand how the electrical system works in our cars, so that the resultant symptoms can be more readily recognized. I might interject something here that deserves attention by everyone as they work on electrical problems that occurs with battery related problems on their cars, and I capitolize this statement. NEVER DO THE "TRYING TROUBLESHOOTING METHOD" when diagnosing a problem. You NEVER try something if you don't know what you are doing. You HAVE TO BE CERTAIN when you hook up a wire, or you are playing with a fire about to happen. There is a formula for figuring wattage, and watts is heat. If one tries something and gets a wire connected across a shorted condition, then that is fire time. Immediate fire time. If you have a 60 amp battery, and you connect that wire between the plus side and gound side, then you have 3 thousand 6 hundred watts of energy being burned. That is a red HOT wire. form

[John Kirchhoff]

Don made a very good point about troubleshooting. When I work with people on economic and nutritional matters concerning livestock, I tell them "If you're gonna do something, do it for a reason". In other words, you need to have an expectation as a result of what you do. Sometimes that expectation includes the possibility of nothing, such as with the gentleman currently looking for the short in his Lark's lighting system. Disconnect the headlights and if nothing happens or changes, then the headlights aren't the problem. Nothing is instrumental in the process of elimination.

But I guess that's the power of this forum. If I know nothing about something, there's plenty of knowledgeable people out there that do and often times their real life, practical experience is more valuable than any shop manual ever printed.

[forrest]

Gentlemen thanks for the short coarse in electricity and ohms law. The reason for the question is I bought a full set of SW gauges for my speedster because the old stuff was not there and didn't realize it had an amp meter at the time i ordered the gauges. Of coarse SW sent all the guages and a volt meter in place of an amp meter. Well in the coarse of new wire loom and new gauges along with alternator and 12 volts I got lost.

I chose to use volt meter because it seems more like a fuel gauge for electricity. I connected all the wires that were on the amp meter and srink wraped them and used tubbing as a extra prcaution.

All said and done there was not even a little smoke when I tried her out for the first time. Luck was with me, everything worked as designed. all the gauges gauged and all the motors moted and the engine even purred like a kitten. Every thing worked the first time which blew me a way. Light turn sig parking lites brake you name it.

I lied the clock does not click or keep time, and the radio is in radio heaven some place.

thanks again guys

[John Kirchhoff]

Glad to hear things are working to suit you Forrest. In the end, all that matters is if you're happy with what you have. That doesn't mean the rest of us can't have some fun bantering back and forth, but if you're happy with poking a stick in the gas tank for a gas guage, more power to you. And yes, I have a tractor with one of those fuel sticks!