Ammeter shunt install help (2 Viewers)

[Stevesnj]

I haven't been able to test my new alternator at work so I bought this ammeter/volt combo gauge with 200amp shunt. I don't want to hook this up incorrectly and need clarification on the Chinese directions. I attached the wiring diagram and can figure out the negative but the yellow wire shows it goes to the alternator but where? I assume it's for voltage but could mount to post B on the alternator for amps. The red seems to be just for power and voltage. Any help would be appreciated

View attachment 877406
View attachment 877406

 

[landcrshr]

That diagram shows the shunt being inline with the ground connection. I don't think that will work for an alternator (when installed).

Actually I think that is a DC motor in the diagram.

 

[Stevesnj]

Oh. The description said for automotive DC applications for voltage and amp readouts.

 

[gahi]

A shunt is installed in one line. You would put this on the negative cable. The plus and minus off the shunt are just for the gauge and not for the actual positive, and negative of the battery.

 

[Stevesnj]

So I can put on a separate negative cable from the battery to the shunt then the other side of the shunt to earth ground say fender or frame?

 

[gahi]

No, the current would then bypass the shunt. This meter is going to tell you the total amps going thru the system, and not the alternator output.

 

[JTeeg]

Wire the Yellow and Black wires to the small screws of the shunt, with the black wire on the battery side of the shunt. Wire the Red wire into any keyed voltage source. Splice the shunt into the negative battery cable using the large terminals on the shunt.

 

[Stevesnj]

So this is the wrong gauge?

 

[Stevesnj]

Wire the Yellow and Black wires to the small screws of the shunt, with the black wire on the battery side of the shunt. Wire the Red wire into any keyed voltage source. Splice the shunt into the negative battery cable using the large terminals on the shunt.

Would this give me the alternator amp output or the system amperage like gahi stated? And anyone know if negative side amp output is okay to monitor?

 

[landcrshr]

So this is the wrong gauge?

Yes, wrong gauge.

That gauge is intended to monitor load current. The alternator is a current source.

 

[gahi]

And anyone know if negative side amp output is okay to monitor?

Its fine to monitor, but it wont tell you much. If you were trying to see how much a stereo system pulled, and how much battery you've used when the car is not running/charging then this would be the correct gauge. Otherwise, you would want a inline ammeter. It would be installed in the line from the alternator to the battery.

What are you trying to determine? Only if your alternator is charging?

 

[Stevesnj]

Yes, wrong gauge.

That gauge is intended to monitor load current. The alternator is a current source.

Well I will just use it as is

Its fine to monitor, but it wont tell you much. If you were trying to see how much a stereo system pulled, and how much battery you've used when the car is not running/charging then this would be the correct gauge. Otherwise, you would want a inline ammeter. It would be installed in the line from the alternator to the battery.

What are you trying to determine? Only if your alternator is charging?

I planned to use it to see monitor the alternator amp output. Apparently I need a positive side shunt shifter. I want to make sure my alternator is putting out the amperage lets say when I get a winch and use it, and other higher amp draw loads like A/C, defroster and soon to be seat heaters.

 

[Pin_Head]

The meter is shown measuring the current in the - side of the charging circuit. That won't work for automotive applications, but you can flip the wires so it measures current in the + side. Connect the B+ lug of the alternator to one side of the shunt. Connect the other side of the shunt to the + side of the battery. Connect the red and yellow meter wires on the two sides of the shunt and connect the meter black to the - side of the battery. You might have to reverse the red and yellow meter wires if the meter reads - amps when it should be +.

 

[gahi]

Pin_Head. Where would the meter ground to for its power though?

 

[Pin_Head]

The meter gets its power from its connections to the + and - side of the battery, like any other device. The current is indicated by the voltage drop across the shunt, which would be the red and yellow meter leads in the new wiring diagram. The voltage is indicated by the potential between the red and black leads, which also power the LED display.

 

[JTeeg]

The meter is shown measuring the current in the - side of the charging circuit. That won't work for automotive applications, but you can flip the wires so it measures current in the + side. Connect the B+ lug of the alternator to one side of the shunt. Connect the other side of the shunt to the + side of the battery. Connect the red and yellow meter wires on the two sides of the shunt and connect the meter black to the - side of the battery. You might have to reverse the red and yellow meter wires if the meter reads - amps when it should be +.

The meter gets its power from its connections to the + and - side of the battery, like any other device. The current is indicated by the voltage drop across the shunt, which would be the red and yellow meter leads in the new wiring diagram. The voltage is indicated by the potential between the red and black leads, which also power the LED display.

I do not believe this will work. I believe the Red wire supplies voltage to power the meter. The Black and Yellow wires sense the voltage drop across the shunt and the Black wire also serves as a common return for meter power. With the shunt spliced into the positive lead from the alternator there will be very little voltage difference (~ mV) between the Red power lead and the Black (common) lead of the meter. Better quality meters will have four wires: 2 to power the meter and 2 to measure the voltage drop. This meter uses the Black lead as both a common return for meter power and to sense the voltage drop; hence why it needs to go into the negative side.

 

[Pin_Head]

Nah. The yellow wire can sense the voltage drop between either reference point + or -. I'm betting it will work; if not you can send it back. The red and black see battery voltage because they are connected to the two ends of the battery.

 

[gahi]

Not in this case. If it had four wires, then yes you could put it in the positive wire from the alternator. If you connect one side of the shunt to positive and the other to negative it will short.

 

[Pin_Head]

no short. One end of the shunt goes to alternator B+ output; the other goes to the battery +.

 

[gahi]

I agree that setup like that it would read the amps flowing out of the Alt. But the gauge itself also needs a ground somewhere for its own power. And this particular unit seems to be setup up to run on the negative circuit because the ground is common.