What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

G3X Amps Scale Factor with VP-X & PPS

Dad's RV-10

Dad's RV-10

Well Known Member
Installation includes G3X, VP-X, VP PPS and B&C 60 amp alternator.

The GEA24 is connected to the Alternator Current pins on the Vertical Power PPS (pin 18 & 19). "Shunt 1" in the G3X config is selected to "Alternator Amps." The indicated amps appear to be considerably higher than what would be expected. The amp indication is also showing 4 amps with the engine not running. I would assume this should be Zero?

I think the G3X Scale Factor needs to be adjusted but I'm not 100% what value to set. The PPS manual has a small chart that shows "Scale 1 A/mV."

In the Shunt 1 Calibration menu, the default Scale Factor displays Multiplier 1.00. When changing the Scale Factor drop-down from "Multiplier" to "mV/Amp," the default value is .50. The displayed Sensor Values differ depending on wherever Multiplier or mV/Amp is selected.

I'm not sure if I'm interpreting the info in the PPS manual correctly but I tried temporarily selecting Scale Factor to "mV/Amp" and setting 1.0 vs. the default .50. That changed the Calibrated Value from 4.0 to 2.0.

I'm not sure this is how I should have the Scale Factor set? If it is the correct setting, I would guess I'd need to adjust the Zero Offset to -2.0 to zero-out the displayed 2 amps?

Any help is appreciated.


Default Multiplier.jpg Default mV Amp.jpg Adjusted Mv.jpg PPS AMPS.jpg PPS Chart.jpg
 
Last edited:
mburch said:
Is this really a shunt, or something else?
Click to expand...

The best explanation I can give with my limited understanding of the PPS is that it's a "virtual" shunt. In other words, it's wired directly to the PPS with no physical external shunt, as per Vertical Power's recommendation.
 
Based on your images, it seems like you need to set the scale factor to 1.0 mV / A, and then use the zero offset value to make it read zero when no current is flowing. You can see that the GEA 24 is sensing 2 mV, which isn't surprising given the stackup of tolerances likely involved.
 
mburch said:
Based on your images, it seems like you need to set the scale factor to 1.0 mV / A, and then use the zero offset value to make it read zero when no current is flowing. You can see that the GEA 24 is sensing 2 mV, which isn't surprising given the stackup of tolerances likely involved.
Click to expand...

Thanks, Matt. That's what I had temporarily tried (in the third image above) but I wasn't confident I was setting it correctly.

I'll go back and make the change and see how it works.

FYI, it's not much info but from the PPS manual, "The PPS provides the alternator current (shunt) output, which shows the amount of current the alternator is providing to power the devices and charge the battery."
 
Maybe a dodgy output driver in the PPS (by design).

Do what Matt said and then see what the PPS/G3X reports when the alternator is running. Use a current clamp/voltmeter to measure the current flow in the "B" wire to confirm the amps displayed.
 
bjdecker said:
Maybe a dodgy output driver in the PPS (by design).

Do what Matt said and then see what the PPS/G3X reports when the alternator is running. Use a current clamp/voltmeter to measure the current flow in the "B" wire to confirm the amps displayed.
Click to expand...

I don't have a clamp meter but I should still be able to get a close estimation. We ran out of VP-X circuits, so a few consumers are wired through a fuse block . But I should be able to run the engine and look at the VP-X to see if I'm in the ballpark .

Matt; To be clear, you're suggesting a Scale Factor setting of 1.0 mV/A based on the info in the PPS chart? If so, that's why I had done so previously but I wasn't sure I was interpreting the chart correctly.

PPS Chart.jpg
 
Follow up:

Selected Scale Factor to mV/Amp and set value @ 1.0.

Adjusted Zero Offset to -2.0.

Ammeter now reads zero with the engine not running and the indications with the engine running are much more in line with expectations.

Appreciate the help.
 
You must log in or register to reply here.
Back
Top