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Capacitance fuel sensors

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rick(at)beebe.org
Guest

Posted: Wed Apr 13, 2016 6:23 am Post subject: Capacitance fuel sensors

Does anyone have any experience with capacitance fuel sensors? My 2001 

GlaStar has them (from a company called Centroid) and they don't seem to 

be working right. I'm not sure if there's any troubleshooting I can do 

or if just replacing them is the right option. They're supposed to put 

out 0 (empty) to 5 (full) volts but one of them seems to be stuck at 

4.75 volts. The other fluctuates around semi-randomly so the gauge will 

read 1/4 then full then 1/2 and so forth.



If replacement becomes the only option this new system from Belite 

caught my eye:



http://www.beliteaircraftstore.com/capacitance-fuel-probes/



Any thoughts on that?



--Rick

speedy11

Joined: 29 Jun 2015
Posts: 62
Location: Port Orange, FL

Posted: Fri Apr 15, 2016 8:19 pm Post subject: Capacitance fuel sensors

Rick - 

 I installed the Princeton capacitance probes on my RV-8 and they are so unreliable as to be worthless.  Their only value is to close the hole cut in the adapter plate to accommodate them.

 I have calibrated them a dozen times - emptying the tanks and refilling them to the top one gallon at a time (mine have optional five point calibration).  I talked to Advanced Flight Systems (probes display on the AFS monitor) and to Princeton (when I could get them on the phone) and followed their instructions precisely.  Out of caution that I might be doing it wrong, I asked a friend to do the calibration without any input from me.  The results in all cases were the same and I get fuel gauge indications exactly as you described.  

 The concept of capaciitance fuel probes is simple and straight forward.  They should be simple to setup and should function without malfunction.  However, I have not talked to anyone who has good results from a capacitance system.

 The Belite probes are interesting in that you can get them in various lengths and they can accept multiple bends.  However, that makes me wonder how they can accurately sense the fluid level since the output is linear.

 But, I'm not an engineer.

 I have a fuel leak at the fuel probes so maybe it is time for me to buy the Belite probes and give them a try.  Worst case is I will have exactly what I have now - nothing.

 Fortunately, my fuel flow readings are accurate to about 0.2 gallons over a two hour flight.  So, I use the fuel flow reading to track my remaining fuel.

 We'll be curious to learn what you decide and how well your fuel system works.

 Stan Sutterfield

 Daytona Beach

 

 

     	  Quote: 	
		  Does anyone have any experience with capacitance fuel sensors? My 2001 

  GlaStar has them (from a company called Centroid) and they don't seem to 

  be working right. I'm not sure if there's any troubleshooting I can do 

  or if just replacing them is the right option. They're supposed to put 

  out 0 (empty) to 5 (full) volts but one of them seems to be stuck at 

  4.75 volts. The other fluctuates around semi-randomly so the gauge will 

  read 1/4 then full then 1/2 and so forth.

  

  If replacement becomes the only option this new system from Belite 

  caught my eye:

  

  http://www.beliteaircraftstore.com/capacitance-fuel-probes/

  

  Any thoughts on that?

  

  --Rick

donjohnston

Joined: 13 Dec 2009
Posts: 231

Posted: Sat Apr 16, 2016 1:07 am Post subject: Re: Capacitance fuel sensors

 	  speedy11 wrote: 	
		  Rick - 

 I installed the Princeton capacitance probes on my RV-8 and they are so unreliable as to be worthless.  Their only value is to close the hole cut in the adapter plate to accommodate them. 	




It sounds like you had these problems from day one, right?



I have Princeton capacitance probes as well. They work fine with no problems so far.

ceengland7(at)gmail.com
Guest

Posted: Sat Apr 16, 2016 4:57 am Post subject: Capacitance fuel sensors

On Sat, Apr 16, 2016 at 4:07 AM, donjohnston <don(at)velocity-xl.com (don(at)velocity-xl.com)> wrote:

 	  Quote: 	
		  --> AeroElectric-List message posted by: "donjohnston" <don(at)velocity-xl.com (don(at)velocity-xl.com)>

 speedy11 wrote:

 > Rick -

 >Â  I installed the Princeton capacitance probes on my RV-8 and they are so unreliable as to be worthless.Â  Their only value is to close the hole cut in the adapter plate to accommodate them.

 It sounds like you had these problems from day one, right?

 I have Princeton capacitance probes as well. They work fine with no problems so far.

Uh.....

chaskuss(at)yahoo.com
Guest

Posted: Sat Apr 16, 2016 6:04 am Post subject: Capacitance fuel sensors

Rick,

 If you are using auto fuel with ethanol in it, the ethanol content will totally mess up the capacitance senders. It's not the fault of the brand you are using or the design of the senders. This is an issue with ALL capacitance fuel sender systems operating in the presence of fuel with ethanol in it. The only cures are to either eliminate the use of ethanol laced gasoline OR to install a set of float style sending units.

Charlie

 speedy11 wrote:

 > Rick - 

 >Â  I installed the Princeton capacitance probes on

 my RV-8 and they are so unreliable as to be worthless.Â 

 Their only value is to close the hole cut in the adapter

 plate to accommodate them.

 It sounds like you had these problems from day one, right?

 I have Princeton capacitance probes as well. They work fine

 with no problems so far.

 Read this topic online here:

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billhuntersemail(at)gmail
Guest

Posted: Sat Apr 16, 2016 6:44 am Post subject: Capacitance fuel sensors

Did you bend the probe in the place where it should not be bent?  

Bill Hunter  On Apr 16, 2016 9:03 AM, "Charlie England" <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote: 	  Quote: 	

On Sat, Apr 16, 2016 at 4:07 AM, donjohnston <don(at)velocity-xl.com (don(at)velocity-xl.com)> wrote:

 	  Quote: 	
		  --> AeroElectric-List message posted by: "donjohnston" <don(at)velocity-xl.com (don(at)velocity-xl.com)>

 speedy11 wrote:

 > Rick -

 >Â  I installed the Princeton capacitance probes on my RV-8 and they are so unreliable as to be worthless.Â  Their only value is to close the hole cut in the adapter plate to accommodate them.

 It sounds like you had these problems from day one, right?

 I have Princeton capacitance probes as well. They work fine with no problems so far.

Uh.....

billhuntersemail(at)gmail
Guest

Posted: Sat Apr 16, 2016 1:25 pm Post subject: Capacitance fuel sensors

Another thought on capacitance probes...



If they never worked right then I would think the probes were bent in the do

not bend area.



If they worked well at one time and are unreliable now then there might be

water in the system.



If they work now but are very inaccurate, did you calibrate them using auto

fuel (or some other liquid) and are now using 100LL (or some other liquid).

When calibrating they need to be calibrated using the liquid you intend to

run.  If you change your type of liquid AVGAS/MOGAS/JETA/WATER or other

containments then they will always read wrong.



.



Cheers!!!



Bill  Hunter

--

rick(at)beebe.org
Guest

Posted: Sat Apr 16, 2016 5:30 pm Post subject: Capacitance fuel sensors

I know you may be addressing Stan's issues but some of it may apply to 

me. I just bought the plane in December. The seller had bought a 

replacement gauge so he knew there was a problem but I don't know for 

how long. I tested the installed gauge and it's fine.



No water shows up when I sump the tanks. As far as I know it's never had 

mogas in it. Always 100LL. It's very perplexing.



--Rick



On 4/16/2016 5:19 PM, William Hunter wrote:

[quote] 



 Another thought on capacitance probes...



 If they never worked right then I would think the probes were bent in the do

 not bend area.



 If they worked well at one time and are unreliable now then there might be

 water in the system.



 If they work now but are very inaccurate, did you calibrate them using auto

 fuel (or some other liquid) and are now using 100LL (or some other liquid).

 When calibrating they need to be calibrated using the liquid you intend to

 run.  If you change your type of liquid AVGAS/MOGAS/JETA/WATER or other

 containments then they will always read wrong.



 ..



 Cheers!!!



 Bill  Hunter

 --

billhuntersemail(at)gmail
Guest

Posted: Sat Apr 16, 2016 7:17 pm Post subject: Capacitance fuel sensors

A capacitance fuel probe is just a small metallic wire sticking down the

center of a larger diameter metallic tube. 



Even if you run MOGAS today (or kerosene or water or vodka) it does not

matter next week what happened today once the offending liquid is removed

and the original liquid is installed in the tank.



All the capacitance probes measure is the resistance between an inner

conductor (wire) and an outer tube that is also a conductor because a given

liquid will have a certain resistance between the outer conductor and the

inner conductor and that resistance will change as the liquid in the gas

tank rises up the probe(s) as you fill or empty the tank.  



Has your capacitance probes ever read correctly?



If when building the airplane the builder was too cheap to buy 100LL and

used MOGAS or water or beer to calibrate the fuel probes (pouring in 5

gallons at a time...looking at the reading on the fuel gauge...then pouring

in 5 more gallons...repeat) then the system was calibrated based on the

liquid that was used.  If he used 100LL to calibrate the system and then now

the readings are various and unreliable then the question would be where are

the lowest point of the probes located...are they at the very lowest point

of the tank???  If so then there might be some water puddled there at the

very lowest part of the tank and if that just happens to be where the fuel

probe bottom is located then there might be some water puddled around the

very bottom of the fuel probe and this water is screwing around with the

resistance readings of the probes.



If there is no water in the fuel and lets say you have always run MOGAS and

the fuel probes were calibrated using MOGAS and this day you dump in 50

gallons of AVGAS then you could expect to see a difference in the

max/mid/low quantity indications of your gauges...once you have burned or

dumped out that fuel load and have refueled with MOGAS then the gauges would

read correctly because the liquid in the tanks is the correct resistance.



.



Cheers!!!



Bill  Hunter

--

rick(at)beebe.org
Guest

Posted: Sat Apr 16, 2016 7:32 pm Post subject: Capacitance fuel sensors

On 4/16/2016 11:15 PM, William Hunter wrote:

 	  Quote: 	
		   Has your capacitance probes ever read correctly?


	


I presume the builder and the subsequent buyer (his son, actually) 

wouldn't have let the plane go 14 years with wrong gauges. The rest of 

his craftsmanship is too good for that.



 	  Quote: 	
		   If when building the airplane the builder was too cheap to buy 100LL and

 used MOGAS or water or beer to calibrate the fuel probes (pouring in 5

 gallons at a time...looking at the reading on the fuel gauge...then pouring

 in 5 more gallons...repeat) then the system was calibrated based on the

 liquid that was used.


	


Actually calibration is a lot simpler than that with this system. 

There's an 'empty' pot that you adjust with no fuel in the tank until 

the gauges (which are really just relabeled volt meters) read empty. 

Then fill the tanks and adjust the "full" pot until the gauge reads 

full. One of the needles wasn't pointing to full and I was able to 

adjust that. But it often seems to drop to 1/4 and then go back up. I 

guess I'm concluding that maybe the sender is broken and that inner wire 

is moving places it shouldn't.



--Rick

wrmaxwell(at)bigpond.com
Guest

Posted: Sat Apr 16, 2016 11:05 pm Post subject: Capacitance fuel sensors

Not  quite so Bill. The         probe is measuring capacitance, not resistance, hence the name.

         

         Bill

       

     On 17/04/2016 1:15 PM, William Hunter       wrote:

     

     [quote]       [quote]--> AeroElectric-List message posted by: "William Hunter" <billhuntersemail(at)gmail.com> (billhuntersemail(at)gmail.com)  A capacitance fuel probe is just a small metallic wire sticking down the center of a larger diameter metallic tube.   Even if you run MOGAS today (or kerosene or water or vodka) it does not matter next week what happened today once the offending liquid is removed and the original liquid is installed in the tank.  All the capacitance probes measure is the resistance between an inner conductor (wire) and an outer tube that is also a conductor because a given liquid will have a certain resistance between the outer conductor and the inner conductor and that resistance will change as the liquid in the gas tank rises up the probe(s) as you fill or empty the tank.    Has your capacitance probes ever read correctly?  If when building the airplane the builder was too cheap to buy 100LL and used MOGAS or water or beer to calibrate the fuel probes (pouring in 5 gallons at a time...looking at the reading on the fuel gauge...then pouring in 5 more gallons...repeat) then the system was calibrated based on the liquid that was used.  If he used 100LL to calibrate the system and then now the readings are various and unreliable then the question would be where are the lowest point of the probes located...are they at the very lowest point of the tank???  If so then there might be some water puddled there at the very lowest part of the tank and if that just happens to be where the fuel probe bottom is located then there might be some water puddled around the very bottom of the fuel probe and this water is screwing around with the resistance readings of the probes.  If there is no water in the fuel and lets say you have always run MOGAS and the fuel probes were calibrated using MOGAS and this day you dump in 50 gallons of AVGAS then you could expect to see a difference in the max/mid/low quantity indications of your gauges...once you have burned or dumped out that fuel load and have refueled with MOGAS then the gauges would read correctly because the liquid in the tanks is the correct resistance.  .  Cheers!!!  Bill  Hunter   --

billhuntersemail(at)gmail
Guest

Posted: Sun Apr 17, 2016 4:04 am Post subject: Capacitance fuel sensors

 	  Quote: 	
		   The probe is measuring capacitance, not resistance, hence the name.

 
	


!!!DANG!!!  My bad…I thought we were talking about “resistant-ance probes”…  As Anna Rosanna Danna would say… “well…never mind”

 

You are right…I misread my Westberg MFG capacitance probes instruction manual…it does talk about the resistance values of the medium being measured…. “The fuel sender works by supplying a small amount of precise power to the outer aluminum tube of the probe and the amount of this power is induced into a second conductor inside the tube (and insulated from it) and it depends on the resistance values of the medium's separating the two conductors a microprocessor in the head of the probe measures the induced potential amplifies it and sends it to the gauge.  As the amount of fuel in the probe decreases from burn off the amount of air increases does continuously changing the amount of power being induced.

 

Well I have learned…when I am trying to pee with the Big Dawgs on the Aeroelectric list I am bound to get some over spray sometimes….

..

 

Thanks for keeping me honest!!!

 

Bill  Hunter



 

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Bill Maxwell

Sent: Sunday, April 17, 2016 12:05 AM

To: aeroelectric-list(at)matronics.com

Subject: Re: Re: Capacitance fuel sensors

 

Not  quite so Bill. The probe is measuring capacitance, not resistance, hence the name.



Bill

On 17/04/2016 1:15 PM, William Hunter wrote:

[quote] 	  Quote: 	
		  --> AeroElectric-List message posted by: "William Hunter" <billhuntersemail(at)gmail.com> (billhuntersemail(at)gmail.com) A capacitance fuel probe is just a small metallic wire sticking down thecenter of a larger diameter metallic tube.  Even if you run MOGAS today (or kerosene or water or vodka) it does notmatter next week what happened today once the offending liquid is removedand the original liquid is installed in the tank. All the capacitance probes measure is the resistance between an inner 	
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EQUIPMENT_FUEL_PROBE_Westberg_Capacitance.pdf

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stephencliverichards(at)g
Guest

Posted: Sun Apr 17, 2016 5:15 am Post subject: Capacitance fuel sensors

We did have a capacitance sensor not sure the make but the zero setting pot whent intermittent so reading kept varying so replaced with a resistor type.

Clive 



From: William Hunter (billhuntersemail(at)gmail.com)

Sent: â€Ž17/â€Ž04/â€Ž2016 13:12

To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)

Subject: RE: AeroElectric-List: Re: Capacitance fuel sensors



 	  Quote: 	
		   The probe is measuring capacitance, not resistance, hence the name.

 
	


!!!DANG!!!  My badâ€¦I thought we were talking about â€œresistant-ance probesâ€â€¦  As Anna Rosanna Danna would sayâ€¦ â€œwellâ€¦never mindâ€

 

You are rightâ€¦I misread my Westberg MFG capacitance probes instruction manualâ€¦it does talk about the resistance values of the medium being measuredâ€¦. â€œThe fuel sender works by supplying a small amount of precise power to the outer aluminum tube of the probe and the amount of this power is induced into a second conductor inside the tube (and insulated from it) and it depends on the resistance values of the medium's separating the two conductors a microprocessor in the head of the probe measures the induced potential amplifies it and sends it to the gauge.  As the amount of fuel in the probe decreases from burn off the amount of air increases does continuously changing the amount of power being induced.

 

Well I have learnedâ€¦when I am trying to pee with the Big Dawgs on the Aeroelectric list I am bound to get some over spray sometimesâ€¦.

..

 

Thanks for keeping me honest!!!

 

Bill  Hunter



 

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Bill Maxwell

Sent: Sunday, April 17, 2016 12:05 AM

To: aeroelectric-list(at)matronics.com

Subject: Re: Re: Capacitance fuel sensors

 

Not  quite so Bill. The probe is measuring capacitance, not resistance, hence the name.



Bill

On 17/04/2016 1:15 PM, William Hunter wrote:

[quote] 	  Quote: 	
		  --> AeroElectric-List message posted by: "William Hunter" <billhuntersemail(at)gmail.com> (billhuntersemail(at)gmail.com) A capacitance fuel probe is just a small metallic wire sticking down thecenter of a larger diameter metallic tube.  Even if you run MOGAS today (or kerosene or water or vodka) it does notmatter next week what happened today once the offending liquid is removedand the original liquid is installed in the tank. All the capacitance probes measure is the resistance between an inner 	
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