Fuel and water tank sending units

[sailby2]

Hello,

Need a bit of assistance understanding what type of sending units Jeanneau used for the diesel and water tanks on a 2008 SO 42i. I am trying to change over tank monitoring from the original equipment Schieber panel to my Victron Cerbo GX. If the sending units are resistive-types, they should be able to directly connect to the Cerbo GX which would make the transfer pretty easy.  My thought is the block connector with al the sending unit wires running to the Schieber panel could be used to re-route the data to the Cerbo.  

Anyone have knowledge about the sending units or have experience getting a Cerbo GX to monitor tank levels?

Thanks in advance.

[Trevor]

Hello sailby2,

For reference of work donw by some clever people before us check out this thread.

jeanneau.proboards.com/post/62538/thread

As for using the CerboGX for tank measurement it is very easy now they have the Victron GX Tank 140. The beauty of this interface is not only does it make interfacing to the Cerbo GX easy (allowing access to VRM) but I believe it allows an NMEA2000 interface so it can appear on modern MFDs as well.

It would be a good project to document if you have the inclination as I am sure many would really like to see how you do it.

Tank geometry casue a nonlinear sensor output compared to tank level. One of our forum members, Mistroma, graphed that non linearity and produced arduino software to compensate for the error. That was a very nice touch i think. You could refer to this thread

jeanneau.proboards.com/thread/6741/scheiber-panel.

You do have access to people in this forum who have done some serious work to improve the tank readings on boats of that era.

One of the features of the Victron GX Tank 140 is the ability to provide for custom programming to compensate for the non linear nature of the sensor reading due to tank geometry. That is seriously important for the fuel gauge on the SO42i (like the SO42DS) because it dreadfully inaccurate. A great feature by Victron I think.

Regards,

Trevor

[Mistroma]

My calibration calcs. might be better than nothing but I suspect every Jeanneau 42 boat will be different.

The length of fuel sensor float arm is adjustable and the arm can also be bent. I think mine was near full extension and fitting pretty much requires it to be at full length (unless someone at Jeanneau trims it a bit with pinchers ). Length will probably be similar for most 42s. However, the arm wasn't straight and had a curve. I actually adjusted the curve even more in an attempt to linearise the reading on the original Scheiber unit.

I suspect that Jeanneau guys just guess where to drill holes for the water tank level screws. I'm basing that on the fact that neither tank is even vaguely close to 25%, 50% or 75% and both tanks are completely different.

[sailby2]

Gentlemen,

Thanks for the in-depth information.

As for the fuel tank level accuracy, the gauge for me is at best, a gross indicator of fuel in the tank and I’d still use the calculated hours/burn rate figure for safety.

The water tanks are another thing altogether and the information you’ve passed on will help me get more consistent readings.

Regards,