electronic gurus, mating gm level sensor

[canadamatt]

I want to use a gm 90ohm fuel level sensor but keep my 02 fuel gauge. What series of magic and resistor trickery do I need to do? I'm assuming something similar to using a pot to figure out the proper resistance to get the 02 tach to be used on a 6cylinder.

Thx

Matt

[TobyB]

Do you know more about HOW the GM sensor changes resistance?

(like, 90 at empty, 220 at full or something like that)

I might have known once, but I gots no clue now...

t

[oldguy]

The GM sensor is 0ohms empty 90ohms full later GM vehciles have a 40ohm empty and 250ohm full. The 02's acording to this guy is 75 empty and 0 full.

http://www.02restoration.com/restoration-tips/fuel-and-exhaust/bmw-2002-fuel-sending-unit-repair/

So... the gauge would read fine with a GM sensor hooked upto stock except the gauge would move backwards. Empty would be full and vice versa.

I imagine a small resistance inversion circuit could be made up.

[TobyB]

hmmm, that's actually a bit tricky.

I'd start by looking at your GM sensor to see how hard it would be to

either rewire or alter the linkage on.

Then if that didn't work, I'd look at the gauge.

As in, what does it do when you reverse

the polarity on it... carefully...

Depends on what's inside it electrically, I guess.

t

[PatAllen]

actualy what you need is an inverted adjustable current source.

LM334 does work well for such "application"...just need to know how to do it

[canadamatt]

Thanks guys. Summit has some senders that I could make work, 70-5, 75-10, etc. I asked Dakotadigital for some magic but they don't currently offer anything (great guys btw).

Pat..I'll look into LM334 , thanks!

Just a side note, I just assumed someone would offer a 'blackbox' that can mate different gauges and senders. I would think they would sell a ton of them. Most guys bite the bullet and buy a $50 gauge or a $100 sender.. if someone offered a $40 solution, they would probably sell a ton.

Matt

[TobyB]

Matt, before you go nuts, look at the mechanical layout of the gauge.

Usually the sensing arm is just stiff wire, so it's easy to bend it around

so that the sender works 'backwards'. I made an Alfa sender work

in the 122 by doing that...

hth,

t