Craig,
You might already be aware of this, but in my judgement, the shifting
problem is not related to the EFIS, but is an artifact coming from the
capacitance sensor, based on fuel type.
Interesting that they mentioned it would work with the capacitance probes.
Did they ever tell you that it can handle a 0-5V input (or at least a
voltage input range)? It would be nice to know if this is the case, since
then the Odyssey could be used to compensate for the fuel usage linearity
issue if someone were to go the pressure sensor/amplifier route.
The Odyssey has two fuel inputs. Each one could have a different transfer
curve (would need to check, to be absolutely sure). If you are only using
one cap probe, you should be able to switch back and forth between the two
inputs, depending on which type of fuel you are using. This would handle two
of the 3 conditions conditions anyway ( such as a full tank of AVGAS or one
of Mogas10%). It would require operator intervention, though, to manually
make the switch based on the condition.
Mogas fuel with ethanol should have a higher conductance than without. I
assume it is the conductivity change that affects the capacitance probe
measurement. If this was the case, then I suppose someone could do some
testing on mogas (and avgas, to see if it is the same as non-ethanol mogas),
and come up with a graph of conductivity vs. fuel type. Using this info,
that other circuit you are talking about might be able to dynamically change
its output based on conductance, and feed this to the EFIS, which will
further process the tanks non-linearity. It might only take a small
proportional shift to do the job, but would depend on the tests.
It is nice to know the Odyssey might handle the voltage input. I hope that
is the case. Let me know if they gave you more info on this.
Regards,
Greg
_____
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of craig bastin
Sent: Wednesday, August 06, 2008 2:24 AM
Subject: RE: Europa-List: sight tube
Greg
> I was told it would work fine with the capacitance type sender but
readings will vary
>depending on fuel type used, which i believe has been covered quite a bit
here already. It is possible though that the distributor has it wrong.
One thing i was considering was another circuit between
the EFIS and my capacitance sender so i can calibrate the sender to the fuel
type to get a more accurate reading depending on AVGAS / MOGAS / Blend of
the two
contents in the tank itself.
craig
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com]On Behalf Of Greg Fuchs
Sent: Tuesday, 5 August 2008 2:34 PM
Subject: RE: Europa-List: sight tube
Yes, it looks like I would be able to use the same input conditioning for an
EFIS that you used for the PIC. I would need both the 12V regulator (sensor
and Burr-Brown amp) and 5 volt regulator to use the clamping diodes.
I looked up info on the Odyssey again, and it will handle up to two tank
inputs, but it wants resistive inputs to its engine management system.
Remembering back, this is another reason I went with a standard float type
sensor.
That said, I think an analog fuel level gauge would look nice (and fit) on
the center console, close to the fuel valve. Could simplify, and get rid of
the clamp circuit. Linearity of fuel used might be my only problem then,
and that is where reverting back to the PIC circuitry may have to happen.
Chasing my tail in this paragraph. :-)
If I had stuck with the Dynon EFIS idea, it would have made this part
easier.
Greg F
_____
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of Tony Krzyzewski
Sent: Monday, August 04, 2008 4:44 PM
Subject: RE: Europa-List: sight tube
> My current plan is to go with an MGL Avionics Odyssey. I bet I can take
the
> sensor output and slightly re-scale it to match the Odyssey input needed,
> but have not looked at it yet.
If you are using a system that a 0-5v input and has it's own scaling
capability (such as the Dynon) then all you need is the power supply,
pressure transducer, amplifier and clamping diode part of my circuit. I'd
just add a 22k ohm resistor in the output line to limit the current.
Fill the tank and then adjust the potentiometer on the amplifier to give you
5v at the input of your instrument. Once you have done that you can follow
the linearisation process provided by the instrument manufacturer.
Tony
href="http://www.matronics.com/Navigator?Europa-List";>http://www.matronhref
"http://forums.matronics.com";>http://forums.matronics.com
href="http://www.matronics.com/contribution";>http://www.matronics.com/c
|