Help with ammeter not working

[lndwarrior]

I have a 40 amp shunt and 40 amp ammeter. This is a new install and the ammeter is not working.

I have checked the polarity and it is correct.

The shunt has four terminals. Two for the main power and two for the ammeter.

I can't remember why (parts on hand?) - but I connected the ammeter wires to the main power terminals. Since it is just a brass bus bar I didn't think this would make any difference in connecting the ammeter wires.

Am I wrong? Is the fact that I didn't connect to the two smaller terminals the reason my ammeter is not working?

Any other ideas?

Tia
Gary

[GalinHdz]

Originally Posted by lndwarrior

Is the fact that I didn't connect to the two smaller terminals the reason my ammeter is not working?

The smaller terminals are at specific points on the shunt to provide the correct output to your indicator. So, more than likely.

[lndwarrior]

Originally Posted by GalinHdz

The smaller terminals are at specific points on the shunt to provide the correct output to your indicator. So, more than likely.

I'm far from an electrical expert but I can't see how there could be any significant difference between 2 connections on a block of brass a half inch a part.

On the other hand it's possible, I just don't know.

[az_gila]

If it is the Dynon shunt the difference is essentially zero. The two screws at each end go into the same large block of brass.

[lndwarrior]

Originally Posted by az_gila

If it is the Dynon shunt the difference is essentially zero. The two screws at each end go into the same large block of brass.

Yea, that's it.

[GalinHdz]

Originally Posted by az_gila

If it is the Dynon shunt the difference is essentially zero. The two screws at each end go into the same large block of brass.

The voltage difference is in millivolts with 1 millivolt per amp as the most common shunt specification. So, "essentially zero" is not zero when you are measuring values that small. I have the exact same shunt for my SkyView and it is a 60A/60mV (1 millivolt per amp) shunt. Before you try anything, check the quality of both lead connections first.

The lead connections are at a very precise location so they can provide a calibrated output. If not, the manufacturer would just have you connect the ammeter leads to the main connectors. If connected wrong you will get erroneous reading which can range from too high (full scale) an amperage to no amps at all. But you do what you think is best.

[az_gila]

Originally Posted by GalinHdz

The voltage difference is in millivolts with 1 millivolt per amp as the most common shunt specification. So, "essentially zero" is not zero when you are measuring values that small. I have the exact same shunt for my SkyView and it is a 60A/60mV (1 millivolt per amp) shunt. Before you try anything, check the quality of both lead connections first.

The lead connections are at a very precise location so they can provide a calibrated output. If not, the manufacturer would just have you connect the ammeter leads to the main connectors. If connected wrong you will get erroneous reading which can range from too high (full scale) an amperage to no amps at all. But you do what you think is best.

I disagree... the resistance is based on the cross-section of the material the current flows through.

The drop in the big heavy portion of the end metal is negligible compared to the drop - which is millivolts like you say - of the relatively skinny bar connecting the two end chunks of metal.

Anyway, even if the difference is measureable if wouldn't cause the ammeter to not work, which was the OP problem. If your comments are correct then the ammeter would be reading slightly high, rather than no reading.

If the Skyview is working (most likely) then there are only two wires involved. I would check the crimps and Dsub pins on those two wires.

[vic syracuse]

It really shouldn't matter on the connection. Is it connected to the EMS box for the Dynon? If so, I have had the box fail with regards to the ammeter and I do believe there is a problem.

Vic

[GalinHdz]

Originally Posted by az_gila

Anyway, even if the difference is measureable if wouldn't cause the ammeter to not work, which was the OP problem. If your comments are correct then the ammeter would be reading slightly high, rather than no reading.

I agree with this. Also, many of these installations, mine included, have the two leads connected through small (1/2A) fuses. If his is connected that way and they blew then he would get no amperage indication as he reported.

Originally Posted by vic syracuse

It really shouldn't matter on the connection. Is it connected to the EMS box for the Dynon? If so, I have had the box fail with regards to the ammeter and I do believe there is a problem.
Vic

That happened to a friend's DYNON EMS so very possible.