Amp meter readings

I'm comparing the amp reading from my VP100 against what my GRT is saying the alt is producing and it's not what I'd expect. With everything on, the VP says something around 32amps but the GRT only reads around 19 being produced. I figured the GRT would show the same being produced . Can someone who knows the workings give me a clue. I'm sure the alt is working properly but I may have an issue with the setup or something. Thanks

Are the two amp sensors on the same feed wire??

What Mike said. Additionally, a wiring diagram would be needed for a good analysis.

Thinking about it... I know there's only one Hall effect/affect? Sensor on the alt line which came with the GRT system. The VP is reading what the system is just using. It doesn't sense what the alt is making. At least this is how I understand it.

I guess another way of asking the question would be... If an airplane had one instrument that only measured the Amps being drawn by things that were turned on and an amp meter that was only measuring what the alternator was producing, would these readings be the same. IE radio, lights, fuel pump, etc. are pulling 32 amps so the alt should be showing 32 amps being produced to match it.

The GRT should read slightly higher, as it also sees the charging current going into the battery. Check the set up numbers in the EFIS. Did you set it up fo 50 amps but forget to loop the wire thru the sensor twice?

Cfrisella said:

I guess another way of asking the question would be... If an airplane had one instrument that only measured the Amps being drawn by things that were turned on and an amp meter that was only measuring what the alternator was producing, would these readings be the same. IE radio, lights, fuel pump, etc. are pulling 32 amps so the alt should be showing 32 amps being produced to match it.

Click to expand...

Not necssarily. The alternators output could be higher if some of the current is going to the battery. It could also be lower if some of the current was coming from the battery. The later shouldn't happen in many cases, but could in certain cases.

I lot of this depends upon where the pickup is located.

Larry