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Garmin G3X Fuel Quantity

rocketman1988

Well Known Member
Has anyone used the G3X with Princeton Capacitance Fuel Quantity sensors?

I seem to be getting conflicting information. According to the Garmin manual, they should work as they are +12v, 0-5v sensors but other info indicates that they need some sort of converter.

Anyone have any experience with them?
 
I hope the Princeton converters work...

...because that's what I'm installing and as far as I can tell from the G3x Installation Guide they should do the job. They're voltage-out converters and the GEA-24 should be able to source 12v to run them.

HTH, and I'll be interested to hear about your experiences if you do install them.

Dave
 
Thats the problem

I already have installed them...several years ago.

I talked to Princeton and they said the sensor IS a +12v input, 0-5v output.

I talked to Garmin and they said the G3X is compatible with a +12v input, 0-5v output sensor.

So it should work directly but then I am getting other info that you need to use a frequency to voltage converter...but the sensor is ALREADY a 0-5v output, so why do you need a converter...
 
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FYI

Update

I just spoke with Princeton. Their sensors do indeed output 0-5v and require very little current from the 12v source. The sensors should function fine, directly, with the g3x when set to voltage mode.

They confirmed that the Princeton sensors DO NOT output frequency so a converter is not required.

They confirmed that they do make a converter that can be used with the EI and Vision sensors which do output frequency but it is not required for Princeton sensors...

FYI
 
They work fine. I had them in a GRT installation but converted 2 years ago to the G3X system. I recall all I had to do was just calibrate the G3X system as I added fuel. I think I had the 2 point sensors.
 
Hey Bob,
Many of us call the Princeton a converter. It converts the 12v to a 0-5v output with resitance change from the capacitance plates.
The G3X reads the 0-5v. You'll see when you calibrate that you enter the output voltage of the Princeton for a given fuel load.
 
Which is

Which, I think, is part of the confusion.

The Princeton sensors require a regulated 12v input and provide a 0-5v output based on the fuel level. They do not need an external "converter".

Unfortunately, adding to the confusion, is the fact that Princeton sells a "converter" to use with some sensors, namely EI and Vision...but...NOT used on Princeton sensors. This "converter" converts frequency to voltage, and is not needed with the Princeton sensors.

Soooo...

The Princeton sensors will work directly with the G3X.
 
Yes, if you have the two-point senders you'll need to calibrate them with the tanks empty and full. You'll calibrate intermediate points through the G3x fuel calibration menu.

Dave
 
Yes, if you have the two-point senders you'll need to calibrate them with the tanks empty and full. You'll calibrate intermediate points through the G3x fuel calibration menu.

Dave
Gosh I don't remember even seeing any buttons or lights on the top of the thing but will check again tonight.

Thought it was just a potted sensor.
Tj
 
I used the Princeton "one point" sensor ... it's just one calibration with empty tanks once installed in the aircraft. The G3X calibration process does the rest of the work when you do the incremental tank fillup operation.

I also confirmed with Princeton that the power draw is plenty low and will be compatible with the 12v supply power coming from Garmin.
 
Gosh I don't remember even seeing any buttons or lights on the top of the thing but will check again tonight.

Thought it was just a potted sensor.
Tj

TJ,

Are your Princeton senders packaged in black plastic boxes? If so, you’ll have to take the cover off to access the button and blinky LED.

Being the gEEk that I am, I measured the sender’s current draw and it *definitely* doesn’t draw more current than the G3x can provide - https://mightyrv.com/?p=3969.

Dave
 
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TJ,

Are your Princeton senders packaged in black plastic boxes? If so, you’ll have to take the cover off to access the button and blinky LED.

Being the gEEk that I am, I measured the sender’s current draw and it *definitely* doesn’t draw more current than the G3x can provide - https://mightyrv.com/?p=3969.

Dave
Mine is the white base with the black potting soil hiding all the guts.
It is buried under a bunch of panels that i will pull off tonight and check again for a button.

I'm a bit of a button spaz... had I known there was a button there I would have already smashed it a hundred times but maybe I missed it.

WIll report back...
 
Ok, reviving this thread since all the info I found here, and other threads, is kinda contradicting, and sometimes confusing... to me ;)

So there I am, amidst my VM1000 to Garmin G3X Touch upgrade... up to now my aircraft was equipped with a dual E.I. indicator.
I've decided to ditch it, and use the fantastic capabilities of the G3X thru the GDU470 and the GEA24.

The aircraft was built using Van's Capacitance Fuel Quantity sensors, which are really only 2 isolated aluminum plates installed in each tank. As an aside, this system has proven very precise and reliable over the past 18 years and close to 1'800 hours.

Now the sensors each have 3 wires, red/white/black. I pinned them directly into the GEA24 (pins 5/7/6 and 8/10/9) according to their color, referenced in figure 26-2.1 of the G3X install manual, and now do get a voltage readout of around 5.3V with the tanks about 1/3 full.

Confused by previous posts mentioning those Princeton converters... does a Garmin G3X Touch configuration still require those, or will it work without?

Emptying, or refilling a tank, and looking for a change in the voltage, should provide a direct answer...
 
Section 21.3.6.2 of the install manual says:

Capacitive fuel quantity sensors require the use of an external transducer to convert capacitance to either a frequency or a voltage.

Fuel quantity transducers that convert capacitance to a voltage of up to 28V may be used, including 0-5V and 0-12V transducers. Examples of this type of transducer include the Skysports and Westach units. [...]

Fuel quantity transducers that convert capacitance to a frequency of up to 50 kHz may be used. Examples of this type of transducer include the Princeton, Vision Microsystems, and EI P-300C units.

The short summary of this is that you can't just connect the plates inside the tank directly to your GEA 24 - there needs to be some kind of box in the middle that converts capacitance to either a frequency or a DC voltage. It's up to you to determine what you have, and configure your system accordingly. So I would start by identifying what you already have installed. It will be some kind of small unit external to the tank, no Proseal work required fortunately.
 
Sensor

Ok, reviving this thread since all the info I found here, and other threads, is kinda contradicting, and sometimes confusing... to me ;)

So there I am, amidst my VM1000 to Garmin G3X Touch upgrade... up to now my aircraft was equipped with a dual E.I. indicator.
I've decided to ditch it, and use the fantastic capabilities of the G3X thru the GDU470 and the GEA24.

The aircraft was built using Van's Capacitance Fuel Quantity sensors, which are really only 2 isolated aluminum plates installed in each tank. As an aside, this system has proven very precise and reliable over the past 18 years and close to 1'800 hours.

Now the sensors each have 3 wires, red/white/black. I pinned them directly into the GEA24 (pins 5/7/6 and 8/10/9) according to their color, referenced in figure 26-2.1 of the G3X install manual, and now do get a voltage readout of around 5.3V with the tanks about 1/3 full.

Confused by previous posts mentioning those Princeton converters... does a Garmin G3X Touch configuration still require those, or will it work without?

Emptying, or refilling a tank, and looking for a change in the voltage, should provide a direct answer...

The g3x is capable of a frequency input or a voltage input. Make sure you have configured it for what you have. I am not very familiar with the EI system but I thought it was frequency based; I may be wrong. Go to redavionics.com and look up the docile ration on their voltage/frequency converters. If you are using voltage, you should see values between 0-5 volts. If you are seeing more than that, something is amiss.
 
EI used to make/provide the capacitance converter BNC/3 wire units for the RV, so sounds likely that is what you already have installed.
You could call them for more info on it.
 
3 pilots, 4 different answers ;)
Just kidding guys, thanks for chiming in.

In a nutshell the system, as installed by the original builder, comprises only 3 elements:

  • a pair of Van's Capacitance Fuel Quantity sensors, aluminum plates, as sold by Van's at the time
  • 3 electrical wires going directly from the sensors to the FL-2 Dual Fuel Level gage
  • the FL-2 Dual Fuel Level gage

I've been told by the builder that the VM1000 was not able to decipher the signal from the plates, hence he had to use the E.I. FL-2 which was doing the work.
 
  • a pair of Van's Capacitance Fuel Quantity sensors, aluminum plates, as sold by Van's at the time
  • 3 electrical wires going directly from the sensors to the FL-2 Dual Fuel Level gage
  • the FL-2 Dual Fuel Level gage

I've been told by the builder that the VM1000 was not able to decipher the signal from the plates, hence he had to use the E.I. FL-2 which was doing the work.
The vans cap sender’s output is via BNC on the tank, which is where the EI converter is located which converts it to 3 wire freq output.
Check out the FL-2 install manual for more info:
https://iflyei.com/wp-content/uploads/FL-1_OI-II.pdf
 
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Thanks Walt. Yes, the connector on the inner tank rib is of BNC type. So I can deduct that the direct connection from there to the GEA24 will work without any supplemental decoding or amplifying.

Also thanks Bob, I'll be back in the workshop tomorrow, and will try using that option. Effectively the text of the Figure 26-1, page 454 of the manual states "7. EI P-300C CAPACITANCE TO FREQUENCY CONVERTERS CAN BE USED FOR MEASUREMENT OF CAPACITIVE FUEL QUANTITY."
Though those are not EI P-300C, they can hopefully be treated as such.

Edit: In addition to the above, I just found out that FL2 gage is of the CA type (FL-2CA), for which the manual states: was designed to be used with E.I.'s capacitive fuel level sensors and it will operate on a 12 or 24 volt system.
 
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Feedback from the hangar:
Of the many options I selected custom and digital for the tanks...
With the now uncertain level of fuel remaining in say the left tank, the Input Frequency displayed 1.885 Khz.
I then tested the reactivity of the system by emptying short of a gallon, and the frequency steadily increased to 1.979 Khz, so the measurement works as is :)

Next step will be to perform a standard calibration by emptying the tanks, and step filling/value validation. Looking good so far...
 
Of the many options I selected custom and digital for the tanks

If this is a standard RV, you'll probably be better off selecting the most basic "Fuel Quantity (Digital)" item. Either will work, but the "Custom" selections are really only needed for special applications like ferry tanks and the like. The difference will be in how the gauges are labeled.
 
thanks for the input Matt. What would be the difference in the labels?
This today's display (using liters = L):
 

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You can try it for yourself, but typically selecting one of the non-custom configurations will allow pairs of fuel quantity gauges to be joined together as appropriate.
 
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