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  #21  
Old 09-03-2021, 07:29 AM
SledDog SledDog is offline
 
Join Date: Nov 2010
Location: Lac du Flambeau, Wisconsin
Posts: 18
Default Replace Van's capacitive system with Van's standard sender?

rapid_ascent, did you ever find a replacement for the Princeton capacitive converters? I have the same problem: G3X with Van's capacitive plates installed. Princeton is (temporarily?) out of business. The Dynon converters don't look like they play well with Garmin. My tanks have been successfully leak tested. If a converter can't be sourced, it looks like the only viable option is to install Van's standard senders and abandon the capacitive system.
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  #22  
Old 09-03-2021, 08:26 AM
rapid_ascent rapid_ascent is offline
 
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Location: Dublin, CA
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I haven't found a solution yet. I called Vans and they don't appear to sell anything any longer. I also called Electronics International. The guy there gave me a part number, IMC-V but I couldn't find anyone who sold it.

I may have to roll my own converter, but I'd prefer to not get distracted with going down that path.
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Ray Tonks
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  #23  
Old 09-03-2021, 11:17 AM
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jaradtke jaradtke is offline
 
Join Date: Nov 2009
Location: Lutz FL
Posts: 153
Default

Dynon sales one... https://shop.dynon.com/products/capa...acitive-plates
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  #24  
Old 09-03-2021, 11:23 AM
SledDog SledDog is offline
 
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Location: Lac du Flambeau, Wisconsin
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Default Dynon converters appear not to work with Garmin.

Jeff, thanks for the info. Unfortunately, I havenít found anyone who has made the Dynon converter work with a Garmin panel. Maybe somebody has figured out how to make it work.
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Roger Grahl
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  #25  
Old 09-05-2021, 02:10 PM
rapid_ascent rapid_ascent is offline
 
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Does anyone have reports on using the Dynon converters? Do they put out a voltage output?
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2020 Donation Paid
Titan IOX-370, Dual PMAGs, 9.6:1 Pistons, FM-150
RV-7 Fuselage in progress
* Cabin Interior - In progress
RV-7 SB Wings
* Both Wings fully skinned
* Fuel Tanks Complete - No leaks finally
* Ailerons Complete
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  #26  
Old 09-06-2021, 12:20 PM
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rzbill rzbill is offline
 
Join Date: Nov 2005
Location: Asheville, NC
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A little lesson first.

All capacitive level measuring systems use the metal probes (be they plates, wire or tubes) as the variable capacitor of a linear oscillator circuit sometimes called an rc oscillator.

The output of that oscillator circuit is a voltage that varies in a sinusoidal pattern at a particular frequency. Change the capacitance and the frequency changes. Few instruments are set up to accept the variable frequency signal.

Many display instruments will accept 0-5 volt DC as an input from a sensing device.

SO, a second conversion is needed to change from variable frequency to variable voltage.
This is done by a ...wait for it... frequency to voltage convertor. These usually rectify the signal and then average it.

A capacitive measuring system that goes from metal in liquid contact to a DC voltage has all three of the above items. Probes, oscillator, freq to volt.

VANS plates are only the first 1/3 of the pie, same as the 2 bare wires on the Princeton.
The converter (oscillator and freq to volt) is the other 2/3. It is built into the hub of the Princeton. With VANS plates, you have to provide a separate convertor.

I have the Dynon converters feeding my GRT EIS 4000 and then displayed on my GRT Efis ..es. They work fine. Perfect? No, but the alternative is resistance floats that can't see the top 5 gallons.

I scratch built and bench tested Jim Weirs KitPlanes converters 14 years ago. They work. I was going to use them until I found the miniscule Dynon units. They were cheap compared to my time for finishing the Weir units.

While bench testing, I needed to know what capacitor to use for simulating my Vans plated tanks. I measured the dry capacitance at 180 picofarad. Fuel is supposed to double that to 360 picofarad. Those are the values I used for testing.

Hope this helps.
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  #27  
Old 09-06-2021, 12:32 PM
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Thermos Thermos is offline
 
Join Date: Jan 2005
Location: KASH
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Quote:
Originally Posted by rapid_ascent View Post
Does anyone have reports on using the Dynon converters? Do they put out a voltage output?
They do. I considered the Dynons but saw some reports in VAF of problems with them, and the Princetons seemed to get better reviews. You might rescan the forums for pireps on the Dynons.

One good thing about the Dynons is they're much easier to install than the Princetons...no extra box to mount since the electronics are directly attached to the BNC connector. All you need to do is run three wires from your GEA fuel measurement inputs to the wing roots.

HTH

Dave
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  #28  
Old 09-06-2021, 12:55 PM
rapid_ascent rapid_ascent is offline
 
Join Date: Mar 2008
Location: Dublin, CA
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Bill,

Given your results maybe its worth giving the Dynon converters a try. I'd rather have a solution than another project of rolling my own. I've looked at the Jim Weir circuit and considered it. I tend to prefer the Princeton approach so if I was to roll my own I'd probably go down that path. I'm thinking now I'll buy one of the Dynons and do a little evaluation.

BTW thanks for the capacitance values. The empty capacitance is the main required number that I was missing. The doubling of the capacitance from empty to full I figured out as a result of the dielectric constant of fuel being approximately twice that of air.
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Ray Tonks
2020 Donation Paid
Titan IOX-370, Dual PMAGs, 9.6:1 Pistons, FM-150
RV-7 Fuselage in progress
* Cabin Interior - In progress
RV-7 SB Wings
* Both Wings fully skinned
* Fuel Tanks Complete - No leaks finally
* Ailerons Complete
* Flaps Complete
RV-7 Empennage - Complete (a little fiberglass work left)
Vans Training Kit # 2 - Complete
RV-7 Preview Plans
Vans Training Kit #1 - Complete
EAA Sheet Metal Class - Complete
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  #29  
Old 10-08-2021, 06:54 PM
tdragger1966 tdragger1966 is offline
 
Join Date: Oct 2020
Location: Denver, CO
Posts: 30
Default

Just got an email from someone at RED Avionics. Looks like they have picked up manufacturing capacitive probes from Princeton. https://www.redavionics.com/s/shop
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