Fuel Gauge Calibration

[Dellquay13]

In theory you could calibrate the stick in the same way, just add a notch every 10 litres from empty.
The problem is how do you define accurate? The sender and gauge (or stick) just tell you how high the top of the fuel is in your tank, not the quantity.
My sender is very accurate, I can see the precise reading and watch it slowly rise. I can see it fluctuate as the boat rocks. The interpretation is what caused the issue. The Cerbo averages over 10 seconds by default, so rocking goes away. After calibration it also converts the fuel height to litres, giving a more meaningful reading that can be used for planning.
The old gauge also showed 1/4 full when only 20 litres out of 125 were present. That was accurate as a height reading and very consistent. Same as the uncalibrated stick.

I’m impressed with the accuracy and linearity of your resistive sender. 180ohms +\- 0% Was that from the data sheet or an actual reading?
You can calibrate a dipstick to show actual litres not depth, I did it on my first speedboat and the 4no 25l petrol tanks using the same technique as you starting at empty and adding 2 litres at a time. Attempt 1 quickly failed using permanent marker which just washed off in petrol, on the 2nd go I notched the stick.

 

[lustyd]

That’s the actual readings as I added fuel, I was very surprised that it used effectively the whole range. Started slightly above zero possibly due to cable length, and finished slightly below 180 when the float hit the top of the tank before it was completely full. Very close though.
Haha I can imagine me using a marker initially to check before committing to cutting notches plotter is easier to use than a stick though…

 

[PaulRainbow]

Do these N2K gauges use your existing sender(s)?

No, you have to get the data onto the N2K bus. Analogue senders can be used on the N2K bus if you connect them using something like an Actisense EMU1, or in the case of tank senders, the Victron Cerbo. Others are available.

 

[PaulRainbow]

I assumed it would be a "no", the same as running 2 gauges off a single station sender unit as the resistance is no longer as expected...? But if Paul R's works, he's the expert! I can see you could recalibrate the Cerbo to read a modified resistance, but not sure how the original analogue gauge would read correctly.

You can calibrate the Cerbo easily, it just needs to know the resistance at various levels. Not connected my fuel sender to the Cerbo, they are connected to an Actisense EMU1, which does not affect the analogue gauge because presumably the EMU1 doesn't impose a resistance. I can connect/disconnect the EMU and it makes no difference to the gauge readout. I would expect the Cerbo to be the same, but haven't tried it.

 

[lustyd]

Ah to be fair I didn’t actually try it, might give it a go tomorrow. Everything I read said doesn’t work but no harm in trying

 

[paulbrown22]

You can calibrate the Cerbo easily, it just needs to know the resistance at various levels. Not connected my fuel sender to the Cerbo, they are connected to an Actisense EMU1, which does not affect the analogue gauge because presumably the EMU1 doesn't impose a resistance. I can connect/disconnect the EMU and it makes no difference to the gauge readout. I would expect the Cerbo to be the same, but haven't tried it.

Amazing, thanks for the additional details Paul - an EMU-1 is on the list too for my Yanmar engine, so sounds like I should be covered by one or the other .