G3X Amps Scale Factor with VP-X & PPS

[Dad's RV-10]

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 if 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.

 

[mburch]

Is this really a shunt, or something else?

 

[Dad's RV-10]

Is this really a shunt, or something else?

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.

 

[mburch]

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.

 

[Dad's RV-10]

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.

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."

 

[bjdecker]

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.

 

[Dad's RV-10]

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.

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 what I had done so previously but I wasn't sure I was interpreting the chart correctly.

 

[mburch]

Matt; To be clear, you're suggesting a Scale Factor setting of 1.0 mV/A based on the info in the PPS chart?

View attachment 65580

Yes, that would be correct for the stated behavior of the device.

 

[Dad's RV-10]

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.

 

[lipper03]

Any thoughts on tests with a bench power?
I'm doing that now, and can't get values to line up. I've started at an offset of -7.5amps, which I think matches the intent of the PPS device, but when the battery amps moves with load change under bench power, but not without power, that doesn't make sense to me. The VPX and power supply amps all make sense and align, so at least I think I know what I'm shooting for with the alt and battery amps.

I do notice at the higher loads, the battery amps seem to line up, so maybe I have to test with higher loads vs these small ones? And the alternator maybe needs a different offset? (I just put it back to 0 offset, sensor value when power supply is off is .012V so it's reading ~12amps, and when on .003V so ~3amps, so something is fishy any ideas?)

Both amp inputs set to -7.5 amps offset and 1 mV/A in G3X Comments:	Loads	External Power Supply ON/OFF	Alt amps	Alt amps expected	Batt amps	Batt Amps expected	Vpx amps reading	Power supply amps reading	Buss Voltage
Alt amps not reading what expected, load of 6-7 amps seems reasonable, so VPX and power supply readings are in line with expected values (this is the case for all tests)	Essential (G3X screens, G5, etc.), AVI (NAV1/COM1/2, etc.), AVI batt (IBBS)	ON	-3	-7	0	0 to +1	6.3	7.1	14.2
Load reduced, Alt amps reading what I’d expect now, but did not change with the load change, which isn’t expected, and battery amps changed when AVI turned off, which is not expected, should have stayed close to zero.	Essential, AVI batt (IBBS)	ON	-3	-3	-3	0 to +1	2.9	3.5	14.2
Testing IBBS turned off, no major changes to readings, this is expected, kept off for further tests so that it would not take a load vs the main battery when the power supply is turned off	Essential Only	ON	-3	-3	-3	0 to +1	2.9	3.4	14.2
Power supply turned off, load of 6-7 amps, battery matches expected, but alt amps should show 0, as there is no power coming in	Essential, AVI	OFF	+4	0	-6	-6	6.3	0	12.9
Load reduced, alt amps changed, closer to zero, but should not have changed when should be zero, battery amps did not change, should have reduced with load reduction.	Essential Only	OFF	+1	0	-6	-3	2.9	0	12.9