PDA

View Full Version : Capacitive Fuel Adapters



CharlieWaffles
02-09-2011, 07:21 PM
Does the AF EFIS systems work ok with capactive fuel senders? Are there specific adapters that are needed? I've read that there is a Dynon one, but I also see Vans selling one now for less - http://www.vansaircraft.com/cgi-bin/catalog.cgi?ident=1297187079-234-564&browse=ei&product=ei-fuelgauge. Will these (IE P-300C) work with the AFS setup?

Trevor Conroy
02-10-2011, 05:04 PM
Yes it sure does! We have many customers with capacitive fuel senders. We just need to know ahead of time so we can cut a few jumpers internally on the EFIS engine board. Adapters are required and we recommend either the Dynon adapter or one we sell. They are $165/ea and you'd need two.

rv8iator
10-24-2012, 01:04 PM
I did not specify capacitance fuel probed when I ordered my AF 3400. Does it need to go back for mod in order to use the capacitance sender? Or can I use the Dynon capacitance converters without the need for a mod. RV-8 is complete so I cannot refit w/ float senders.

Shawn McGinnis
10-29-2012, 10:34 AM
You will need to cut the jumper for the AF-3400 to be able to read the cap level adapters. I have sent you an e-mail that explains the process. Alternatively, if you want to have us cut the jumper its not a problem.

wooody10
02-07-2013, 03:03 PM
Shawn, I have a pair of 4500's and if I remember correctly, I think that I specified that I would be using cap fuel senders, but I am not sure. Could you please send me a copy of the procedure referenced above so that I can check my 4500.

Rob Hickman
02-07-2013, 10:53 PM
Check the current AD value in the Tank calibration menu. With nothing connected to the tank sensor wire it will be almost zero if configured for capacitance tanks. If it is configured for floats it will be around 1800.

rshannon
02-10-2013, 06:25 PM
Trying to diagnose new problems with my Westach gauges, which worked fine for over 160 hrs. Is the zero figure given above meant to be with power and ground connected to the gauge sender, just not sensor wire, or with everything disconnected from gauge sender? (I have AD_value 3600 in the latter case.)

Rob Hickman
02-10-2013, 07:38 PM
The number should be close to zero with the wire disconnected from the EFIS, if the EFIS is setup for voltage input on the fuel gauges. Normally you can’t connect two gauges to the same probe.

Some of the Westburg probes were setup to output a resistance and act like a standard float sending unit. You need to figure out what you have and how it works.

rshannon
02-11-2013, 05:52 PM
According to the invoice sent to the orig. builder, I have Westberg 395-5SB5 senders, which are described as "Capacitance Fuel Level Sender...240 ohm, 12VDC." (I've left out a couple physical size refs.) These have worked fine for >160 hrs, with a 1.5K ohm resistor in the 12V supply line, as instructed back in '08. (I note the current schematic shows the resistor in the EFIS sense wire. If that's significant, it didn't affect performance before now.)

The left one now reads anywhere from 0.0 -- 3.x gal., with actual 10-11 gal. in the tank, and, even more oddly, the right one, which was fine for ~3 hrs. after the tank repairs (see below) suddenly failed to 0.0 in flight attitude (it's a taildragger) but then recovered on the ground. On the next short leg, it failed again in flight attitude, but recovered on the ground again. Pretty strange, but at least it's reproducible. (Calibrations have not changed.) Any guesses on possible failure modes for that?

Since things worked fine, the tanks did undergo significant repairs for seepage issues and, though the senders were not removed, it's possible one or both got nudged somehow. It would be odd that both would fail from something like that and the original builder secured the bottoms of the tubes slightly above their ends in a small "stalagmite" of ProSeal -- so they're not waving around loose. Prior to reassembly there was no evidence of undesirable tank contact (confirmed even now via borescope) or other damage and the symptoms Westberg describes for undesirable tank contact or concentric tube contact are also not present.

At this point I doubt this is an EFIS/EIS issue -- though the flight/ground attitude thing is strange -- but the problems remain difficult to diagnose. If anyone has suggestions, or is otherwise willing to participate in the hunt, I have measured a set of electrical datapoints in various states. There are no shorts, power failures, or other apparent clues. I haven't yet tried recalibrating because it seems like a long shot, but probably will. Replacing the senders is doable, of course, but would be quite difficult, to say the least.

rshannon
02-11-2013, 09:53 PM
Hmm. With jumpers, I tried swapping the senders from their normal EFIS tank circuit to the opposite EFIS tank circuit, one at a time. I'm getting very different results -- still erroneous -- when they're swapped to the other tank circuit. It seems that if the problem is just in the sender(s) they should exhibit the same behavior regardless of which tank circuit they're on, but that's not the case.

I will carefully re-check the resistor values and the EFIS Engine Sensor plug for integrity, continuity, etc., and if they still look OK, I probably should send this unit back for a checkup, just to cover all the bases before deciding on surgery for the senders.

Rob Hickman
02-12-2013, 06:06 PM
I believe that your Westburg probes actually act like they are resistive probes. You need to figure out exactly what probes you have and how they work. Unhook the probes from the EFIS and make them work with a volt-Ohm meter to verify that they do work.

Do they put out a 0-5 Volt DC signal with fuel or a 40-240 ohm signal?

If they are 40-240 Ohm you cannot connect them to a separate fuel gauge and the EFIS, the EFIS should be configured for float fuel sensors.

Rob Hickman
02-12-2013, 06:08 PM
The resistor in series with the EFIS should only be used when the probes output a 0-5V DC signal.

stickandrudderman
09-10-2015, 05:29 AM
Having just converted from float to capacitance, cut the jumpers as instructed and confirmed that my new sensors output less than 5V I find the following:

I observed the data points changing in calibration page as I filled the tank, but I find that the fuel level display is static, showing a reading of 50 litres that doesn't change as fuel is used. I've run the tank dry to ensure I'm not imagining it. Any ideas?

Shawn McGinnis
09-10-2015, 09:00 AM
Post a picture of your calibration. The values should always be ascending or descending and should change by at least ~50 AD_VALUE per calibrated point. A range of 100 to 900 is standard for a float. 100 to 3000 would be capacitance.

stickandrudderman
09-19-2015, 06:37 AM
This turned out to be user error. I was not moving the cursor across to the columns to the right before copying the data.