Sensing level in a sight tube

[BTalbot]

Here is a capacatice sensor from Turck that is adjustable and can mount to a sight tube.

http://www.turck-usa.com/illustrations/S2620117 (sheet_1).pdf

 

[Brijm]

Thanks to all, for the recommendations.

I think that a float switch is going to alleviate most of my problems with the bubbling oil. I found this switch, which shouldn't be too difficult to add to the sight tube. I'll look for other options (manufactures) as well.
http://tinyurl.com/MeggitFueling