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G3X analog fuel quantity input (cap converters)

Captain_John

Well Known Member
Hey All,

I will need a capacitive to resistive converter for my fuel quantity on my G3X.

I see that the Dynon part number 100654-000 might just do this for an analog input.

Can anyone confirm this for me?

The Dynon part seems to be a better price than the Princeton units.

:confused: CJ
 
It was my impression that you didn't need a converter for the G3X. Maybe someone else with more experience can comment.
 
Well,

The G3X manual says this:

18.3.2.14 Fuel Quantity
The GEA 24 and GSU 73 support fuel quantity inputs from both analog (resistance or voltage) and digital (frequency) sensors. "Float" type resistive fuel quantity sensors are analog devices. Capacitive fuel quantity sensors may be analog or digital devices, depending on whether they output a voltage (analog) or a frequency (digital).
The GEA 24 supports four fuel quantity inputs (FUEL 1 through 4), any of which can be used with an analog or digital fuel quantity sensor.


So it sounds to me like I need to convert the value to resistive, no?

:confused: CJ
 
John,

I recently upgraded to the G3X. I had Vans capacitance tanks with the Electronics International P-300C converter. I was all set. The P-300C converts to frequency so it remains digital for the G3X. This combo has been working great in the G3X, very accurate and almost linear. I think you will need some kind of converter, be it analog or digital, for the G3X. I've heard the Princeton converters also work well with the G3X.
 
CJ,

If you have VAN's metal plate capacitive senders, you need capacitive converters. Either the Dynon or the Princeton ones will work. I recommend you power them separately however and not use the excitation power provided by the G3X system.

The Dynon ones are cheaper but are not adjustable.

The Priceton ones come in different flavors. One with just 2 calibration points and one with more. I used the 2 point models. Make sure you tell the Priceton folks that they are for the Van's senders.

Both Dynon and Priceton convert the capacitance to a voltage output.


Like Pat says above, the EI ones will work as well but I am not familiar with them. They will be wired slightly different than the Dynon and Priceton ones.

The EI ones and some others convert the capacitance to a pulse train output.
 
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I'll say one more thing in favor of the EI converters. There are an unlimited number of calibration points--I used 2 gallon increments, but you can use 1 gallon if you have the patience. This makes the calibration curve extremely accurate if you like that sort of thing, probably not that critical in real life. Also, I calibrated in flight and ground attitudes, so that makes it even more accurate, however, I didn't see a lot of difference between the flight and ground modes just looking at the curves. I'm assuming yours is a -7.

[CORRECTION: Garmin G3X Install Manual states there's a maximum of 50 calibration points--so NOT unlimited!]
 
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Just to clarify....

The Dynon ones are not adjustable. What you get is what you get.

The Princeton ones come in different versions. You can calibrate the converter to the full 0-5V output range depending on how much your probes change capacitance empty to full.

Not sure on the EI ones.

BUT....In all cases, you can still calibrate the G3X for multiple calibration points both for in flight and on the ground to get rid of any non-linear response from the senders. The number of points is dependent on your patience and how much you want to handle the fuel.

Based on what Pat is reporting, I would try the EI ones. I am not that thrilled with the Dynon ones or the Princeton ones. Each have their issues....
 
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Good info, Brian. Yes, on the EI converters you're just reading fixed capacitance (?farads converted to MHz), no adjustments available, but from looking at the points on the calibration curve, it appears almost linear with a slight hump at the "full" range. Also, not sure what those EI converters are running cost-wise these days; back in the day I think Vans sold them for around $75 apiece. I'm sure they're higher now.
 
Wow, I just saw the same thing on Van's parts page! So that's $90 bucks for the pair, I must have paid $75 for the pair more than 10 years ago! 2002 to be exact. :)
 
Well that works for me guys!

I am going to give the EI's a try. The -6 I am flying now has the EI Dual Fuel Gauge and it works very well! As a matter of fact, I would say that it is SUPER ACCURATE!

I will let you know how I fare!

Thanks guys!

;). CJ
 
That was the section I remember reading. Certainly if you want to convert to voltage you will need a converter of some type. My response was in reference to the digital configuration. I'm not sure why they would make a modern piece of equipment that needed a converter that they don't sell.
 
That was the section I remember reading. Certainly if you want to convert to voltage you will need a converter of some type. My response was in reference to the digital configuration. I'm not sure why they would make a modern piece of equipment that needed a converter that they don't sell.

They make the interfaces available for frequency, resistance and voltage which are the common output types of most commercially available fuel level sensors (Van's Cap. Senders Excluded). They have no idea what senders you are going to use. Remember that not all of the experimental market are Van's Aircraft builders.

In almost all cases Van's plates require some sort of converter to work. Other brands of capacitive probes typically come with a built in converter that converts to one of the common interface signals. Those that don't typically have this converter built into the dedicated display head.

I am not aware of any experimental EMS that can accept the raw capacitance output of the Van's senders without some sort of third party converter to change the capacitance to one of the three common interface signals.
 
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