DIY floats
 

I'm exploring various ways to make my own oil tank remote level sensor, and one of them is to just use some float switches (I was thinking eight or so). Individual switches allow me to place them to account for the volume not varying linearly with the height. All the float switches I've found are either large or expensive (or both!). Since it's basically just a float and a micro switch I thought I could just slap a few together myself. Normal wood isn't sufficiently buoyant, but I was thinking polyurethaned cork, foam, or balsa wood might work. And intuition on this out there? Thanks.

If the oil pan is flat then it would not be that bad. I would think you would only need 4 floats unless you’re trying to account for every last drop. Why not go with one float. It should settle out every time you stop at a light or a stop light to get a good eye shot of your level.

Might I ask the reason for doing this?
I think I have a source for micro floats rated for 250*F oil. I will make a call and see if I can get some info sent to my email.

Sorry, I should've mentioned this isn't automotive! It's for my crawlspace heating oil tank. The remote sensors are a little pricey so I thought I'd cook something up. Right now I'm using a web cam and a light on an extension cord. I don't need it often, but it's kind of a crude way to check the level.

Don't reinvent the wheel. There's loads of cheap floats.

Any sporting goods store will have these keychain floats in the boating/fishing section for $2:
https://www.teamskisupreme.net/Mercha...float_navy.jpg

Then there's always toilet floats, but those are too big.

What kind of switch are you going to use and how are you going to integrate it with the float?

I was thinking (if I go this way, as there are loads of technologies) of a metal rod that the floats rode upon via a hole in there center. Then just micro-switches that they trigger. I could weld a sheet metal bracket onto the rod to mount them. I might even be able to just use cable ties to mount the switches, depending. I figured people might have float or even float switch sources so it was worth mentioning. I considered floats in a tube, but that makes installing everything a lot tougher. The hole in the oil tank is quite small (I forget off the top of my head), so anything I use has to fit through it.

Never worked with balsa wood or cork before although I saw a mechanical tank gauge that used a polyurethaned cork for its float.

Really easy would be mercury switches attached to tethered floats like the one you're suggesting. What are those things made of anyway? Want to make sure it'll hold up to the oil. I suspect mercury switches are a bit dear.

I can get tilt switches (not mercury, but that's not important) for $1. Cool. Another option.

Another way to go is to use a single float in a tube and then have it press different switches as it goes up. I was considering adding a little circuitry anyway so it'd flash when it got low, so doing the logic would be easy. As I'd only need one float I could just buy something nice. Obviously I need to sleep on this to ponder all the options.

I forgot this part:

No need to do that. Besides the fact that you'll eventually learn that 1/4 level doesn't mean 1/4 volume just as you do on a car's fuel gauge, the geometry can be figured and the math done to know exactly how much is left.

I once interviewed for a job at a company that only did one thing: Develop software to calculate the volume of fuel left in underground storage tanks based on height. It sounds simple, but it's not. There's odd shaped tanks, tanks not buried perfectly level, etc, and the calculations are insane. They had huge amounts of computing power and loads of expert programmers and geometrists (is that a word?) and mathematicians. I can't say I fully understand why anyone would pay for that kind of service but I imagine that it would be pretty expensive, based on what I saw.

Ah, found it...this is the company:
https://www.warrenrogersassociates.com

About the single float idea... You could use a float with one strong magnet on it to activate small magnetic switches, like these. That would take up less tank space and they are 2 for a buck.