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Where to Purchase Princeton Capacitive Converters

rapid_ascent

Well Known Member
I've been trying to figure out where I can buy a set of the 2 point Princeton capacitive fuel sensor converters. ACS is showing the 5 point version, but I don't need those with my G3X system. I've emailed and left voicemail at Princeton Electronics, but no response. I heard that GRT sold them, but they responded that they no longer sell them. I think Vans used to sell them, but I didn't see them when I searched for them.

Any ideas on how best to proceed?
 
Are you sure you need the converters? The GEA is compatible with capacitance probes like the Princeton. I think you need to provide ships power though, since the GEA power output is somewhat limited.
 
Well that's not good news. :(

Anyone have a set of the 2 point converters sitting on a shelf somewhere that they aren't planning to use.
 
issue

I think that this is a misconception that many have.

The Princeton capacitance probes output 0-5v; for the Garmin setup, no converter is needed.

Princeton ALSO sells "converters" to change frequency output, from other manufacturers, into 0-5v output.

You also need to know that they recommend using ship power for the sensors. They said that the GEA24 does not have sufficient output to drive the sensor.

You may also be able to reset the 5 point sensor...

I spoke with Todd some time ago, and he sent me these supplemental instructions:

Multi Set-Point Supplemental Instructions

The multi set-point feature of the probe allows the selection of 1S, 2S and 5S modes.

1S (Calibrate Empty)

-The output will be 0 volts for empty and approximately 1.5 to 3.5 volts for full. -Used by Dynon and Advanced Flight EFIS Systems.
-Can be used by Grand Rapids Technologies EFIS.
-Has the advantage of not having to empty the tanks to calibrate the EFIS.

2S (Calibrate Empty and Full)

-The output will be 0 volts for empty and 5 volts for full. It is linear between the two. -For use with Grand Rapids Technologies and Chelton EFIS.
-Used with analog gauges and some EFIS that use a calibration table.
-Gives greater voltage range on the output.

5S (Calibrate Empty, 1⁄4, 1⁄2, 3⁄4, and Full)

-Used with analog gauges and some EFIS that use a calibration table. -For use with Grand Rapids Technologies and Chelton EFIS. -Linearizes the output for analog gauges.
-For an EFIS, enter a linear chart in the table.
-Gives greater voltage on the output.

Stratomaster Calibration

-The probe can be re-calibrated an unlimited number of times.
-The only calibration sequence for the Stratomaster version is empty.
-Calibration can be entered or restarted at any time.
-To enter calibration mode, hold the button down while turning on the power.
-The empty set point can take as long as 16 second. All other set points are less than 2 seconds. -Water affects the probe, giving it a reading of full. Water will not hurt the probe. The surface
tension of water will make it hard to be removed from the probe. Gently tapping the probe will help.

To Select the Set-Point Setting:
1. Power off the module.
2. Short the output (yellow wire) to ground.
3. Press and hold down button.
4. While holding down the button, turn power on.
5. After 10 seconds, the lights will turn off. Keep button pressed.
6. The left light will come on, then it will shift to middle, then to the right light and then all lights will light. It will repeat this continually until you let go of the button.
7. Release the button when the appropriate light is on.
8. Turn off the power and remove short to ground from the output.

Left Light = 1S
Middle Light = 2S
Right Light = 5S
Middle & Right Lights = Stratomaster


Knowing what I know now, If I build again, I will use the CiES sensors for fuel quantity...
 
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Bob, thanks for that info. I'll have to check with ACS on the 5 point units. I went back and took a closer look and it says special order so they may not have any stock. I'll give them a call though and see.
 
So I’ll ask again since I may be one of those who don’t understand how these probes work.

If you are using the G3X system with the GEA 24 and capacitance probes like the Princeton or Westach, do you need a converter since the GEA allows a frequency input? What am I missing here?
 
probe

I cannot speak for the westach but my Princeton probes output 0-5v,not frequency, and are compatible with the GEA24, as is...no converter required.

You are also correct in that the Garmin system allows for either voltage or frequency...so there should be no converter required either way...
 
Krea,

There is a difference between the "probe" and the converter. The probe is a passive capacitor. In the case of the Vans kit is a set a plates. Princeton also makes (or did) make a probe which is really just the sensor. The probe then needs to interface to some electronics to make either a frequency or a voltage that can be measured. So some sort of electronic converter is needed before it can be connected to the the GEA module.
 
Krea,

There is a difference between the "probe" and the converter. The probe is a passive capacitor. In the case of the Vans kit is a set a plates. Princeton also makes (or did) make a probe which is really just the sensor. The probe then needs to interface to some electronics to make either a frequency or a voltage that can be measured. So some sort of electronic converter is needed before it can be connected to the the GEA module.

Sorry, but those probes, not the plates, are not just passive capacitors...the electronics are built into the mounting puck.

The Princeton probes require NO converter, as they output 0-5v...go ahead and check the installation manual and FAQs on their website.

http://www.northwing.com/Princeton-Fuel-Level-Probes-Manual.pdf

https://www.princeton-electronics.com/frequently-asked-questions.html

The converter is only required if using vans plates, which are just that...plates.
 
Question for Garmin?? G3X Guy??

Perhaps the G3Xpert will chime in here. I used the Vans capacitance plates setup. Since they are just plates, as Ray said above, they need some sort of electronics to input a voltage across the capacitor and read the output. At the time I built my tanks with capacitance plates, I bought the 5 point set princeton "converters" because I was told by Todd that this would cover all bases, with respect to the EFIS I ultimately decided on. The question for Garmin is "Can the G3X system input a voltage into the plates and provide the reading too, so in effect act as the converter itself?"
 
It looks like there are more variations of the "probe" than I realized. Some with internal electronics and some that require an external converter module. Either way my original post is in regards to the Vans plates.
 

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I doubt that the Garmin (or any other EFIS product) will accept input from from Van's (or any other passive) capacitor "probes".

I'm saying that because I think a coax cable from the probes to the EFIS will probably have more capacitance than the probes.

That is the reason the capacitance-to-voltage (or capacitance-to-frequency) converters are mounted so close to the probes.

If Princeton converters are not available, there was a guy here that was prototyping capacitance-to-voltage converters. Might want to search for that thread (capacitive fuel senders) and contact him.

Finn
 
I have a pair of the original Van's converters from my wing tanks, if you can't find the Princeton ones.

Princeton converters were superior to the Vans converters, in my opinion, but it's better than none.
 
Perhaps the G3Xpert will chime in here. I used the Vans capacitance plates setup. Since they are just plates, as Ray said above, they need some sort of electronics to input a voltage across the capacitor and read the output. At the time I built my tanks with capacitance plates, I bought the 5 point set princeton "converters" because I was told by Todd that this would cover all bases, with respect to the EFIS I ultimately decided on. The question for Garmin is "Can the G3X system input a voltage into the plates and provide the reading too, so in effect act as the converter itself?"
I'm not Garmin but I'll chime in anyway. Capacitors (which is what our capacitive plate/fuel dielectric combinations are) block DC. They pass AC in proportion to the value of the capacitor, or in our case, the amount of fuel which acts as the dielectric. That's why we use AC at some frequency to measure fuel level with capacitive plates.

So if I'm interpreting your question correctly, the GEA-24 can provide a limited amount of power through the +5v sensor power line (50 mA, IIRC) but connecting that line to the Van's plates to a converter like your Princeton boxes will do nothing to provide a fuel measurement

HTH

Dave
 
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You might check with Electronics International, I have the Van's plate installed and they supplied a simple converter to work with their system, no problems in 20 yrs.

From the G3X manual:

For capacitive fuel quantity measurement, a third-party capacitance-to frequency
or capacitance-to-voltage converter is required; the G3X system
does not support direct connection to capacitive fuel tank probes.

Fuel quantity transducers that convert capacitance to a frequency of up to 50 kHz may be used. Examples
of this type of transducer include the Princeton, Vision Microsystems, and EI P-300C units.
 
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You might check with Electronics International, I have the Van's plate installed and they supplied a simple converter to work with their system, no problems in 20 yrs.
Does Dynon still sell converters? They did when I bought my Princeton boxes a few years back.

ds
 
If I remember correctly, my Garmin GDU-370 using the Van's plates has the Princeton converters that I bought from Dynon. That was back in 2013.
 
I think Dynon has their own converter from my searches here on VAF. My impression from before was that these converters were not as accurate as the Princeton, but maybe that is incorrect.
 
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.
 
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.
 
Dynon converters appear not to work with Garmin.

Jeff, thanks for the info. Unfortunately, I haven’t found anyone who has made the Dynon converter work with a Garmin panel. Maybe somebody has figured out how to make it work.
 
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.
 
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
 
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.
 
RED Avionics

In my RV-7A, my right fuel level has always read '0' (on EIS head) and I suspected that the plate/voltage converter on firewall (capacitance system from Princeton) was defective. I contacted RED Avionics (who took over from Princeton Electronics) for a new unit and it finally arrived.

But the calibration instructions were terribly confusing (and worse yet, may be spurious). I emailed RED over Thanksgiving and asked for a call back and sure enough, got a call from Clint (new owner?) within 10 min! Clint emailed me the correct procedure to calibrate my newly installed black box voltage converter. If you need to calibrate for empty and full set points (ie, 2 set points), here is the calibration rubric:

Drain and Empty Tank
Hold Button (on printed circuit board) and power on master
Release button
Left light should be flashing
Press button
Left light will go solid for up to 16"
Right LED should start flashing (Don't press button at this time!)
NEXT:
Fill tank to full with avgas
Now press button
Right light solid for up to 2"
Middle light flash for 2-3"
Middle light blink every 5"
Check EIS for full.

I'm posting for builders/owners who may have run into calibration issues and to give a thumbs up to Clint at RED Avionics for being so helpful (esp on a holiday weekend). The new company appears to be very responsive to customers!
 
Capacitive to voltage converter

Aircraft spruce has the Dynon converters in stock for sale - $50.00. I used them on my RV-7A ( first flight August 2021) and they work very reliably. Followed the calibration procedure for the HDX and EMS220 at 2 gallon intervals from empty to full and they are holding calibration. Phase 1 almost complete.

KT
 
Hey everyone,

Vans Plates Convertors are available, we just close our store on Sundays (EST)
I am working on getting them on Aircraft Spruce as well.

I asked Doug if I could tell you guys this without breaking the rules, and he tells me it's ok.

Clint Rosendall
 
So way back when I built my tanks (2005!) I put in the Van's cap senders.

Getting back into the project this winter, and looking into this issue.

Those that have bought the converters, which ones did you get?

Is this a decent solution? How does it work with the G3X?

My tanks are all done and sealed, but I am wondering if it is worth the time to pull the covers and put in floats while the wings are not mounted and lower skins not riveted (way easier to take off the tanks!).

Thanks in advance.
 
Princeton 2-point converters. No issues at all after 8 or 9 years (I don't recall when I replaced the Dynon converters, which never worked well for me).
 
Red converters back in stock

Talked to Clint yesterday. He said his expecting to receive a big order of new stock. So the Red converters should be back in stock soon.



https://www.redavionics.com/

**UPDATE 4 May 2023. **

As expected RED Avionics converters received. They’re back in stock.
 
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Just ordered the Red Converters

Wrapping up the second fuel tank with the Vans Plates. Ordered the Red converters, curious if anyone has a picture of their converter mounting location?
 
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