With reference to the attached schematic.
I used the voltage divider rule and calculated a volt drop resistor of about 8.12 Ohm in series with the gas measurement device. (RV1 in the circuit replaces the gas sensor). I got a voltage of between 0.7V and 5V for a measurement range of 12-132ohm.
This is only for example. I don't know if the fuel you are measuring is flammable or not? (Diesel, Petrol ???). Calculate the resistor wattage to ensure that they don't heat up too much.
If you require a more precise 0..5V input signal, you will need to use an OPAMP.
The LM3914 will light a led for every 0.5V on the signal pin. Assuming a voltage level of less than 1 volt on an empty tank, the IC will start switching on the LED's as the resistance value of the measurement sensor decreases as the level increases.
The diodes in line with the LED's are all 1N4148 diodes. I did not include current resistors inline with the LED. You will need to calculate the required resistors yourself.
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