Volts to ohms for fuel sender

[Calabashmc]

yes more bars = more fuel. The measurements I took may not be super accurate as I only have a cheap multimeter. The manufacturer provided additional info (post #37). Is this now enough information for someone to come up with a solution?
I can build it if you provide design and willing to try any number of designs but need the diagrams for me to understand.
Thanks

 

[Alec_t]

The setup of the gauge is 100ohms is full tank, 10 ohms empty tank.

10Ω 28.6mA 6 bars

74Ω 20.6mA 0 bars

Do you see the inconsistency? Why 6 bars for an empty tank?

 

[Calabashmc]

Alec_t I don't know what you mean. 6 bars indicates full tank not empty. With 10Ω resistor I get full tank which makes sense as the old style fuel level sensor being a resistive stick and ball would have higher resistance the emptier the tank.
So to reiterate, my fuel level sensor is sonic not resistive and outputs 0.9V when full to 3.8V when empty. My fuel gauge works on the old resistive style with the measurements I have provided.

 

[Alec_t]

The setup of the gauge is 100ohms is full tank, 10 ohms empty tank.

With 10Ω resistor I get full tank

??

 

[BobK]

With 10Ω you get the smallest voltage which is the fewest bars on the display.

Bob

 

[Calabashmc]

No, sorry I got that arse about in my earlier post. Lower Ω means fuller tank. Sorry for the confusion.

 

[Calabashmc]

that's interesting the voltage across the resistor is about 0.25V when showing full and 1.5V when empty.

I would suggest that an op amp capable of 30mA or so with a gain of about 0.4 would do the trick. Probably best to have the op amp drive a mosfet.

this has the advantage of being fairly simple. Lashing up a proof of concept for this wouldn't be too hard. Of course the final circuit would require protection from noise and spikes, but there would be little chance of it locking up (like a uP might)

Can you draw a diagram of this for me? I'll do it but need to know the bits to buy and how to put it together.