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fuel tank Capacitance-to-Voltage Converter data request

jcaplins

jcaplins

Well Known Member
As I sit here in the home office, I have a data request from those of you with the VAN's capacitance plates in the fuel tank and the Dynon converters:
http://dynonstore.com/#!/Capacitance-to-Voltage-Converter-for-Vans-Capacitive-Plates/p/52526438

What output voltage do you get across the 0 --> 21 gallon range?
Voltage increase with fuel or decrease?
Is there a zone where the readings stay the same? (for example: 0-3 gallons or 19-->21?)

I realize different tanks, fuel type, plate size, etc... all affect output, but I'm just looking for a rough idea.

Thanks,
 
Above 16 gallons (in my 9A) each tank's plates are completely submerged and it can't tell the difference - the display just shows "16+"

Now as to the voltage levels, that's a good question, I'll have to go look at mine.
 
Only 16 gallons? I wasn't expecting to hear that. My plates come pretty close to spanning the full height of the tank, and are on the next ribs in from the ends, so I would expect more than 16 gallons before it stopped sensing a change. I guess I'll find out, hopefully soon.

IMG_2895.JPG
 
It's the dihedral. The wing root end of the tanks are full before the tip ends of the tank are full, and that's why the fuel gauges don't register differences above 16 gallons.
 
If I had it to do over again, I think I would have placed one of the capacitance plates further out in the tank, closer to the tip to capture the top end a little better.
 
Ed_Wischmeyer said:
It's the dihedral. The wing root end of the tanks are full before the tip ends of the tank are full, and that's why the fuel gauges don't register differences above 16 gallons.
Click to expand...

The thread is about a fuel tank with a capacitance fuel level sensing system which has a capacitive plate at the inboard and outboard end of the tank to minimize the effect of dihedral on the reading

airguy said:
If I had it to do over again, I think I would have placed one of the capacitance plates further out in the tank, closer to the tip to capture the top end a little better.
Click to expand...

Second rib inboard was the recommended location to prevent damage to the plate by fuel nozzles. The difference between the two locations should be only about 1 gal.
 
RV8

I have the Vans plates, Dynon cap. converters and an MGL EFIS. Mine read from 21 gallons to 0. But they tend to move in increments of one to two gallons at a time. I have never measured the voltage, but if my memory is correct, it varies from zero to five volts
 
brad walton said:
I have the Vans plates, Dynon cap. converters and an MGL EFIS. Mine read from 21 gallons to 0. But they tend to move in increments of one to two gallons at a time. I have never measured the voltage, but if my memory is correct, it varies from zero to five volts
Click to expand...


good to know.
The total output of the sensor is 0-5V, but it is my understanding that the delta min to max when installed and depending on the installation of plates and fuel used, the actual output would be a much smaller range; perhaps 3.2V --> 4.8V (or whatever the case may be).

The calibration should take care of this, and maybe its a moot point, but I just trying to do some calculations before the actual calibration.

Thanks,
 
jcaplins said:
good to know.
The total output of the sensor is 0-5V, but it is my understanding that the delta min to max when installed and depending on the installation of plates and fuel used, the actual output would be a much smaller range; perhaps 3.2V --> 4.8V (or whatever the case may be).

The calibration should take care of this, and maybe its a moot point, but I just trying to do some calculations before the actual calibration.

Thanks,
Click to expand...

Perhaps Dynon has improved their converters, but mine when first installed in 2012 *sucked*...the total voltage range was something like 0.01 volts or something ridiculous, from empty to full. I swapped them out for the Princeton Electronics converters (you first calibrate empty as 0V, full as 5V, THEN go through the tank/EFIS calibration process) and they've been fine since (reading a tad high in mid-range, but that's more than likely just my inaccurate filling of the tanks, and someday I'll re-do the 2-gallons-at-a-time thing).
 
jcaplins said:
Only 16 gallons? I wasn't expecting to hear that. My plates come pretty close to spanning the full height of the tank, and are on the next ribs in from the ends, so I would expect more than 16 gallons before it stopped sensing a change. I guess I'll find out, hopefully soon.

IMG_2895.JPG
Click to expand...

Mine track all the way to 21 gallons. I have never checked the voltage output though.
 
The voltage change on the dynons with vans plates is well less than 5 volts. However, they still work pretty good with data spanning 0 to 21 gal. There is a "kink" in the graph though, so it is not a single linear function. The slope changes at roughly 10 gal. No fault of dynon. Its either tank shape or the point at which the second capacitor plate comes into play.
 
this data is from the dynon config file

user_cal={
valid=1
name=LEFT LEVEL
num_points=8
point={
volts=1.25733
value=0
}
point={
volts=1.29891
value=2.64172
}
point={
volts=1.33885
value=5.28344
}
point={
volts=1.37307
value=7.92516
}
point={
volts=1.38319
value=10.5669
}
point={
volts=1.42351
value=13.2086
}
point={
volts=1.47788
value=15.8503
}
point={
volts=1.68
value=21.1338
}
}
user_cal={
valid=1
name=RIGHT LEVEL
num_points=8
point={
volts=1.2109
value=0
}
point={
volts=1.25137
value=2.64172
}
point={
volts=1.30796
value=5.28344
}
point={
volts=1.33886
value=7.92516
}
point={
volts=1.37586
value=10.5669
}
point={
volts=1.4174
value=13.2086
}
point={
volts=1.46066
value=15.8503
}
point={
volts=1.56666
value=18.492
}

total voltage range is from 1.2-1.5 volts

still seems to work well though, apparently the dynon sensors are sensitive to .01 volts
 
david.perl said:
this data is from the dynon config file

total voltage range is from 1.2-1.5 volts

still seems to work well though, apparently the dynon sensors are sensitive to .01 volts
Click to expand...

Thank you. That is a significantly smaller range than I was expecting.
 
Great information. I can't get my right side to calibrate. I wonder of the voltage converter from Dynon is bad.
 
I initially wired both sides with some wire I thought was adequate, and had to rewire both sides with a better quality wire. Sorry, I can't recall specifics. Just that the wire I initially used was useless and did not work at all. So I believe with these low voltage spreads, conductivity is critical.
 
David Jeff
I'm trying to calibrate my capacitance plates now, using Dynon's converter and the SkyView HDX and when I add 2 gallons SkyView tells me, "the voltage didn't change, do you want to add anyway?" So I kept saying yes for 10 gallons. I could see the voltage was changing about 3/10ths Volt per every two gallons, but decided the calibration wasn't going to work, so I quit after 10 gallons.

I've emptied the tanks. But reading your posts sounds like I should ignore the error message and proceed. Is that right? Will the calibration function work and give me some kind of fuel level reading?

thanks
 
sglynn said:
David Jeff
I'm trying to calibrate my capacitance plates now, using Dynon's converter and the SkyView HDX and when I add 2 gallons SkyView tells me, "the voltage didn't change, do you want to add anyway?" So I kept saying yes for 10 gallons. I could see the voltage was changing about 3/10ths Volt per every two gallons, but decided the calibration wasn't going to work, so I quit after 10 gallons.

I've emptied the tanks. But reading your posts sounds like I should ignore the error message and proceed. Is that right? Will the calibration function work and give me some kind of fuel level reading?

thanks
Click to expand...

Might as well try it and see what you get, but I had pretty poor luck with the Dynon converters...the range it saw from empty to full was extremely narrow.

The Princeton converters worked great, since you can set the 0 point and the full point to span the entire 5V range. Time-consuming to do, though, but well worth it.
 
sglynn said:
David Jeff
I'm trying to calibrate my capacitance plates now, using Dynon's converter and the SkyView HDX and when I add 2 gallons SkyView tells me, "the voltage didn't change, do you want to add anyway?" So I kept saying yes for 10 gallons. I could see the voltage was changing about 3/10ths Volt per every two gallons, but decided the calibration wasn't going to work, so I quit after 10 gallons.

I've emptied the tanks. But reading your posts sounds like I should ignore the error message and proceed. Is that right? Will the calibration function work and give me some kind of fuel level reading?

thanks
Click to expand...

I appreciate your experience for I also tried the Dynon converters. The voltage did not change at all between empty and full. They were both always stuck at about 1.5 V. Since it isn't a serviceable part, I discarded them in favor of the 5-point Princeton senders. I am very pleased with their accuracy.

 
sglynn said:
David Jeff
I'm trying to calibrate my capacitance plates now, using Dynon's converter and the SkyView HDX and when I add 2 gallons SkyView tells me, "the voltage didn't change, do you want to add anyway?" So I kept saying yes for 10 gallons. I could see the voltage was changing about 3/10ths Volt per every two gallons, but decided the calibration wasn't going to work, so I quit after 10 gallons.

I've emptied the tanks. But reading your posts sounds like I should ignore the error message and proceed. Is that right? Will the calibration function work and give me some kind of fuel level reading?

thanks
Click to expand...


My dynon cap sensor converters are connected to a EIS4000 engine monitor and there is only a scaling factor and offset, which basically gives me a linear calibration as my only option. It would be as if I was only calibrating based on 2 points. If I remember correctly I only had something like 0.8 volts range. I have it calibrated to be accurate at 0 and 15 gallons. You should get pretty accurate results connected to a dynon EFIS.

0.15V per gallon seems like too much compared to my results... I would continue with the calibration and see if it works.
 
Fuel Level Calibration with Dynon Cap. to Volt Converter

Okay, I did the calibration yesterday with the Dynon Capacitance to Voltage converters and SkyView HDX. It worked.

Volt ranged only from 1.05 to 1.34. But it appears to be sufficient for the gauge to work. I did get the error messages that says voltage didn't change, but I could see it changing on the screen. And at the end of the process when I hit full, the screen said Calibration Successful.

It does stop measuring at about 17 or 18 gallons. So I fudged the top couple numbers up to 21 but left the bottom half as calibrated. I also have fuel flow so I call the fuel level gauges just a backup.

Note: I had to remove the default fuel level gauges on the HDX screen because they are pins 20, 21 for resistance and then edit and add in new fuel level for capacitance pins 22, 23. And then set the colors for it. All seems fine.
 
sglynn said:
It does stop measuring at about 17 or 18 gallons.
Click to expand...

Two things...when I used the Dynon converters, the mid-range turned out to be pretty useless, as it would stay at 16-17 for a looong time, then go rapidly down to 7-9; and my -7A will measure quite accurately up to almost completely full, not sure why yours stops at 17-18 (plate size not big enough, or not installed close enough to the top skin?).
 
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