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Put the circuit together but the needle only moves just above the E mark! I did use pots for R1, R2, R6, R8 and set the resistance to the values on the schematic and placed a 70Ω resistor across the tank and ground.
Not sure where to go from here!
I added node names (labels) to all of the critical nodes in the circuit. I used LTSpice to compute all of the node voltages if the sender is replaced with a 20Ω resistor, and again if it is replaced with a 100Ω resistor. These correspond to empty and full. Look at the two tables of voltages.
With the table of voltages at all of the nodes in hand you should be able to tell what is not working. Note that I did not intend for you to use pots for R1, R2, R6 and R8. If you had used the 1% fixed resistors, the only one you might have to tweak is R6. If you just put pots everywhere, powered it up, I dont think you can set them to the correct values after the fact. If you preset them to within a % or two within the value on the schematic, you might stand a better chance.
Hello people. I've been following this thread for an answer to my particular problem but it hasn't shown up, so here it is...
I'm building a dashboard for my bus using the SunPro 8219 fuel gauge. I intended to replace the existing sender with one made for the 8219 but then I found out it was near impossible to access the tank. So now I'm looking for some electronics to make the gauge read correctly. Here are the particulars-
Supply v => 12vdc
Sender => 0Ω empty, 88Ωfull
Gauge => 240Ω empty, 33Ω full
Note the inverse relationship.
Mathematically, the relationship works out to y = -2.95x+240
I was halfway thru building the op amp circuit that was in the 3rd or 4th post before I realized the inverse gain might be a problem.
How do I reconfigure the circuit to produce a negative gain?