Amp reading

[bjdecker]

The G3X "default" settings assumes a 50mv/100A shunt -- at 60mv/60A you'll need to do some scale adjustments.

With the engine running, and the alternator field enabled, put the G3X into configuration mode, select Engine & Airframe, GEA 24 Inputs Tab, then Scroll down to Shunt 1.

Does your G3X show something like the attached pic? What's the value for "Sensor Value?"

If nothing, then it's time to chase the wires - Hi to the Alternator, Lo to the Battery side of the shunt. Is the alternator actually running -- volts measured on the "B" lead at 14.4 - 14.6Vdc?

[mfleming]

Originally Posted by bjdecker

The G3X "default" settings assumes a 50mv/100A shunt -- at 60mv/60A you'll need to do some scale adjustments.

With the engine running, and the alternator field enabled, put the G3X into configuration mode, select Engine & Airframe, GEA 24 Inputs Tab, then Scroll down to Shunt 1.

Does your G3X show something like the attached pic? What's the value for "Sensor Value?"

If nothing, then it's time to chase the wires - Hi to the Alternator, Lo to the Battery side of the shunt. Is the alternator actually running -- volts measured on the "B" lead at 14.4 - 14.6Vdc?

If my hi and lo are swapped, would it show zero?
Also, not sure about going to config mode with the engine running… would my engine sensors still work and display?

[bjdecker]

Originally Posted by mfleming

If my hi and lo are swapped, would it show zero?
Also, not sure about going to config mode with the engine running… would my engine sensors still work and display?

It will show a negative number.

Reboot the unit by pressing [nrst]+[menu]+[back] simultaneously. Then press the [menu] button until it says "Configuration Mode"...works great, very useful for checking on things like this in real-time....

[mfleming]

Originally Posted by bjdecker

It will show a negative number.

Well thats a bummer...I'm not getting anything
I've checked the continuing and pin positions on the shut wires...not sure what else to check?

Originally Posted by bjdecker

Reboot the unit by pressing [nrst]+[menu]+[back] simultaneously. Then press the [menu] button until it says "Configuration Mode"...works great, very useful for checking on things like this in real-time....

Great tip, Thanks.

[KatanaPilot]

If you have the shunt wires reversed, it might show a negative number - but if you have a minimum value of zero set on the gauge display range, I don’t think it will display a negative number.

This happened to me recently on our RV-10. Had confirmation of alternator operating with voltage increase, but zero amps. Found shunt to GEA wires reversed. The gauge minimum value was set at zero, so I don’t think it would have displayed negative current reading.

[mfleming]

Originally Posted by KatanaPilot

If you have the shunt wires reversed, it might show a negative number - but if you have a minimum value of zero set on the gauge display range, I don’t think it will display a negative number.

This happened to me recently on our RV-10. Had confirmation of alternator operating with voltage increase, but zero amps. Found shunt to GEA wires reversed. The gauge minimum value was set at zero, so I don’t think it would have displayed negative current reading.

Thanks, you’re right. I went into the config menu and there’s not an option to setup a negative number.

Next time I have my cowl off, I’ll swap the wires!

[mburch]

Originally Posted by mfleming

Thanks, you’re right. I went into the config menu and there’s not an option to setup a negative number.

Next time I have my cowl off, I’ll swap the wires!

If you look at the current calibration page it should show you the raw amps reading, which would indeed be a negative number for an alternator shunt wired backwards.

[jakej]

I have a situation where the amps (70amp alt) are reading ~85 amps in cruise however volts are ok - any ideas, please ?

[mfleming]

Originally Posted by jakej

I have a situation where the amps (70amp alt) are reading ~85 amps in cruise however volts are ok - any ideas, please ?

If you’re using the G3X, you might look at the config page and check your settings for whatever shunt you’re using.

The G3X looks at the shunt and measures the millivolts across the shunt. My shut is 60 millivolts when the shunt is maxed out at 60 amps. The Garmin shunt is 50 millivolts at 100 amps. The G3X needs the info to know what the amps to millivolt factor is. If it’s wrong, the amps will read higher or lower depending which way the error is. I’ve asked The G3experts twice how to figure the factor and have not been given a clear answer yet.

My rudimentary understanding is, my shunt would be a factor of 1 (60 mV/60 amps). The Garmin shunt would be a factor of .5 (50 mV/ 100 amps) but this is the part where Garmin was not clear on.

Hopefully someone with a better understanding of this will educate us.

[mburch]

Originally Posted by mfleming

The G3X looks at the shunt and measures the millivolts across the shunt. My shut is 60 millivolts when the shunt is maxed out at 60 amps. The Garmin shunt is 50 millivolts at 100 amps. The G3X needs the info to know what the amps to millivolt factor is. If it’s wrong, the amps will read higher or lower depending which way the error is. I’ve asked The G3experts twice how to figure the factor and have not been given a clear answer yet.

The software allows you to enter the mV/A value directly, why not just do that?