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JPI EDM-900 & Vans Capacitive Probes - Help Needed

jselvatici

Well Known Member
Hello Folks,

I hope by posting my situation here, I can get some brainstorming going, since JPI seems to be out of resources right now.

Situation:
- Have an EDM-900 with all the connections, including Fuel Quantity indication.

- My aircraft have Capacitive Fuel probes, and had previously installed an Electronics International FL-2CA fuel indicator with their P-300C (little converter thing that takes 3 wires IN and output 2 wires hooked on BNC at the tank). Worked great.

- After EDM installation, can't get it to read the Capacitive probes as the FL-2CA used to do. JPI sent me the schematic to hook up as attached here with red highlights. Also, JPI asked to change the settings to "FREQUENCY". Even doing this and some other "settings" and experiments, no luck.

Question:
- Am I the only one that has an RV with Capacitive Fuel probes and using JPI EDM?

I try to always support the aviation business but I'm a little frustrated with JPI's customer support. I know it's an experimental airplane and basically they have no obligation, but work together would be nice, interested in solve the issue... anyway...

Appreciate if anyone have any idea and I can try test on the airplane and see if I get readings.

Appreciate any information. Thank you.
 

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I think your problem is you need a converter module to convert from Capacitance to voltage. I believe your old fuel gauge was designed to work with the Capacitive fuel sensor so within that gauge was the converter. The gauge you mentioned is different than the one that is designed to work with a resistive sensor.

I don't believe your sensor will work in the Frequency input mode since there is no interface to make the oscillator or create a variable frequency. These detectors can use the variable capacitance to create a variable frequency, but you need some additional circuitry to make the oscillator. There are also converter modules that output voltage which would allow you to use the voltage input mode on your new EDM-900. Either way I think you need some sort of converter module.

I'm making some assumptions here since I don't have all of the information, but I believe I am correct. The only way I can see that you wouldn't need to have some additional converter module is if the EDM-900 supported capacitive fuel probes. That would be different than Frequency or Voltage or Resistance and that doesn't appear to be an option from what you have stated.
 
Temporary Results

Thanks Ray for chiming in.

Last night I did some more testing on this and found some interesting results:

1) For testing purposes, I took the Electronics International “Interface Module” out of the old (E.I. FL-2CA) equipment and installed on P6A according to the diagram attached:
a. 1st I tried with Fuel Level Sensor = Voltage. I could get some very funny readings.
b. 2nd I changed Fuel Level Sensor = Frequency. I could get more solid readings.

2) I was able to “calibrate” the tank as you can see in one of the attached pictures.

3) I need to fly and see if the fuel level will change accordingly.

4) The question to JPI now is: Is there a way to make JPI system works with Vans Capacitive probes without having to use Electronics International "Interface Module"?

I sent an e-mail to JPI with this information and will wait to see what they say. More to come.
 

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Ok so from what Dave said then the converter module (IMC?) which you removed from your old gauge outputs a frequency versus a voltage. So it seems correct that you were able to get it working when configured for frequency input. If that turns out to work and since you already have one maybe you could just buy one more for the other tank and you would be good to go without too much additional expense.
 
Our IMC modules are designed to be powered by 5VDC on the red wire and ground on the black wire. The white wire is the signal wire which outputs a frequency based upon the quantity in the tank. The IMC module is basically the oscillator which creates the frequency. If the JPI unit can accept an actual frequency input, a frequency to voltage converter is unnecessary.

Dave,
Thanks for your input. I will forward this to the email I'm exchanging with JPI and see if they have a solution, which so far not. JPI has asked me to experiment some stuff regarding how to hook up their wiring but no luck so far.

Ok so from what Dave said then the converter module (IMC?) which you removed from your old gauge outputs a frequency versus a voltage. So it seems correct that you were able to get it working when configured for frequency input. If that turns out to work and since you already have one maybe you could just buy one more for the other tank and you would be good to go without too much additional expense.

Ray,
You're correct. At this time, I have one IMC on each tank and that is giving me accurate fuel quantity reading. Just flew yesterday to confirm.
I will keep those installed while I troubleshoot with JPI. I think this will benefit everyone that has Vans Capacitive probes and are looking to upgrade to a JPI equipment.
 
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