Calculating Fluid production with Submersible pressure sensor

Hello:

We use submersible pressure sensor in oil tanks to monitor the level in the tank.

We also have a routine the will estimate the oil production, buts it's not very accurate.

I would like to hear anyone else's ideas on how they might approach this, I would like to be a little more accurate.

Thanks

If the tank is pressurized at all the drop in sensor won't work.
The Wet oil tank at my previous job had a thief hatch but it held at 8 oz. that 8 oz will throw off a drop in.
The best method for level that I've seen is a radar or A differential pressure off a sight glass mount.

These tanks are vented to the outside so they are not pressurized!

I have used these for years, and they always show consistent reading to the 1/2 inch.

I am needing some type of formula that can be applied to show production.

Something like what I am doing now but maybe be a little more precise.

I read the tank level every 15 minutes and subtract the difference from the last tank read.

I disregard any negative as that is probably a tank being emptied.

Would like some new(better) ideas.

Does it happen that the tank is being emptied partly during production?

How do you want to present the production? In volume or volume/time?

"subtract the difference from the last tank read" isn't the produced amount = actual level - level earlier?

When you say Oil are you talking about Crude Oil? Are you trying to do some type of Custody Transfer with your set up?