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Old 10-02-2018, 04:08 PM
Brent Brent is offline
Join Date: Jan 2013
Location: Hanover, Pa
Posts: 35
Default Capacitance fuel quantity

I am having no success calibrating the vans capacitance fuel quantity sensors. I am now wondering if there is any way to check the sensors. Secondly, does anyone have any experience with this system could give me any pointers?

Thanks, Brent
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Old 10-02-2018, 04:15 PM
nilberg nilberg is offline
Join Date: Dec 2012
Location: Katy, TX
Posts: 231

It might be a ?did you plug it in? question, but what EFIS are you using ?

Do you need to convert from capacitance to resistance ?
Bjorn N - RV 7 in progress
Katy, TX
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Old 10-02-2018, 04:47 PM
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sglynn sglynn is offline
Join Date: Mar 2008
Location: Anacortes, WA
Posts: 820
Default Capacitance

I recently did this. Here is link where you can see it.

One thing to note the voltage change was very small and the Dynon gave error messages that it hadn't changed, but it had. The entire voltage range was within one volt but this is sufficient to register volume.

My system is Vans capacitance plates, and Dynon EMS and Dynon Capacitance to Voltage converter connectors.

have fun
Steve Lynn
Flying Phase I
Anacortes, WA
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Old 10-03-2018, 08:40 AM
Djgeib Djgeib is offline
Join Date: Jun 2012
Location: Fernandina, Fl
Posts: 73

I don?t think you?ll read above 18 gallons. Your floats will have topped out by then. If the first 18 gallons are accurate I believe your in good shape.
Doug Geib
RV8 empennage complete
QB wings started
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Old 10-03-2018, 10:35 AM
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Raymo Raymo is offline
Join Date: Nov 2014
Location: Richmond Hill, GA (KLHW)
Posts: 2,164

Originally Posted by Djgeib View Post
I don?t think you?ll read above 18 gallons. Your floats will have topped out by then. If the first 18 gallons are accurate I believe your in good shape.
He doesn't have floats; the capacitance plates do a great job of reading from empty to full but have the disadvantage of not being accurate when using or mixing alternative fuels (e.g. MOGAS).

I second what sglynn said. If you see any change in values, just carry on.
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Old 10-03-2018, 07:32 PM
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rzbill rzbill is offline
Join Date: Nov 2005
Location: Asheville, NC
Posts: 2,675

I breadboarded capacitance converters ala Jim Weir during my construction around 2010.

During that excercise I measured the dry tank capacitance of vans system, also knowing that the capacitance would roughly double when filled with avgas.

If memory serves, the dry tank value was 180 picofarad. Quite small.

I wound up buying and using the Dynon convertors because they were cheap and available in a nice compact package vs all the work to do final fabrication on the Weir breadboarded units (that worked also). The Dynons are not perfect but good enough to satisfy my needs.

Years ago, Brantel posted a volume to voltage curve for the Dynons in his 7 which was a big help in tuning my GRT EIS to work with the Dynon convertors.
Bill Pendergrass
ME/AE '82
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Old 10-03-2018, 08:26 PM
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wjb wjb is offline
Join Date: Nov 2012
Location: Half Moon Bay, CA
Posts: 1,006

I have the Dynon converters, too, but haven't tested them yet.

One way to play with them is to put a test load on them and measure the output voltage. Rzbill quotes 180 pF empty, 360 pF full (plus/minus some biases from the tank connector to cap plates)

An easy tank simulator would be a length of RG-58 coax, which has a capacitance of about 30 pF/foot. Crimp on a connector on one end and connect to the Dynon gauge. 12 ft would give you a "full" tank, 6 would give you an "empty" tank. Simply trim the end to adjust the capacitance (just cut it with a wire cutter; be sure the shield and center conductor don't short when done).

I'll go do this and report back ...
Bill Bencze
N430WB RV-7 #74152 @ KHAF, tip-up; IO-360-M1B; Hartzell CS. !! Phase 1 !!
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Last edited by wjb : 10-03-2018 at 08:30 PM.
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Old 10-03-2018, 09:10 PM
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N941WR N941WR is offline
Join Date: Jan 2005
Location: SC
Posts: 12,887

First, check your wiring and make sure your senders are getting the voltage, ground, and return signal they need.

If they are good, drain your tanks and check to make sure your plates aren't shorted out.

If all that is good, call Dynon.
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
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