Tank volume M³ - S7 300

Hi,
I trying to get my analog value to match the preset value i Kilograms.
Our round tanks (placed horizontal) is messured vertical by 4-20mA

My task is to somehow equal my proces vable with the list.

0mm = 0kg
100mm = 654kg
200mm = 1.802kg
200mm = 3.270kg
...
...
...
2500mm = 48.650kg

How is this posible to set up in a S7 300 PLC
I have 12 tank that look the same.

What is the tank diameter.
Is the tank empty at 4 mA.
Is the tank full at 20 mA.
Cubic meters to Kg can only be calculated if you know the specific gravity of the material.
If it is water then 1 m3 = 1000 Kg.

The above questions need answered in order to make the fomula work.

Depending on the accuracy you need, probably the easiest solution is to use FC103 CDT - Corellated Data Table - which you'll find in the TI - S7 sub-directory of the standard library.

To do this you need to build a table (in a DB) with the weight equivalent to the level in, say, 5 mm intervals. When you feed your height measurement to the input of the CDT it will output the weight equivalent to this value (if it happens to exactly match one of the table entries) or the next higher value in the table.

This would certainly be a lot easier (and quicker) than trying to calculate the weight on the fly.

Formula to compute volume of liquid in horizontal cylindrical tank

D = tank diameter
L = tank length
d = depth of liquid (from bottom of tank)
v = volume of liquid

s = 1 - (2*d/D) ; Radians !
v = L * (D/2)^2 * (acos(s)-(s*sqrt(1-s^2)))

I think that some level sensors have tank formula conversions built-in already. Might be worth investigating.

I just look at FC103 CDT and it resembles something like what I need.

Jesper, I've tried to change the formula for it, but the problem with that bobble bearings can not reach all the way down to the bottom. therefore 4mA = 650kg
Maybe it's better to put the values into a DB and read from it.

But Fc103 not make it all the way
Does anybody have solution for a system table for this?

Frederik, if the sensor cannot reach the physical bottom of the tank, then you just offset the formula:
Example
dMinSensor = 0.1 m (the 100 mm at 654 kg you mention)
d = dSensor + dMinSensor.