levelling 2 tanks with pressure sensor 0-10 V

hi, i'm an new logo user. I install irrigation systems and try to workout a system to level tanks and use the same pressure transmitter also for cutting off cuurent in case of dry running.

The problem is this, I have 2 tanks, tank 1 is a small tank ( only 100 cm  high) for indoor water use and nr 2 is a bigger one (200 cm H2O) for irrigation purposes. If tank 1 is full the water runs to the 2nd tank so there's always water available for indoor use.

In the 2 tanks I installed a submersible OEM-pressure transmitter ( specs in attachment) which is able to detect until 0.4 bar (or 4 m H2O level). output is 0-10 V.

I made a schematic synthesis of what I want it to do, but I can't get it working.

One of the issues is that I cant find how to do the following. If the water in Tank 1 lowers under 0.5 m and still goes lower (= if use of water >filling by the well) and you use a analog comparator you can set it to work between f.i. 0.4 and 0.8 m H2O, but when it occurs that the level goes beneeth 0.4 m it switches off again!

I want to work it as a normal filling system with 3 probes (tanklevel drops under level high, nothing happens, drops to low level it switches on untill level reaches high level again even when it goes a short period under the lower levelprobe.

Has anybody an answer for this problem? 

thanks for the input.

this is the way i wanted to solve the problem. I tried it with delays. The Delay is a good solution to prevent the pump from switcing on and off if the level is reached, but did'nt solve it entirely.

In simulation mode it worked, but once installed it did'nt. I guess it has something to do with settings of the transmitter. It didn't work at all, there was no output on the screen.

dear Sir ,

As I said it's the first time i use this and have never used a PLC before, nor did I learned it.

When I said it didn't work, I meant that my program didn't work. I guess there was a problem with the way I assigned the pressure transmitters.

It's a logo 12/24 RCE , beneeth the green "ok" button it says 6ED1052-1MD08-0BA0.

so I geuss its a 0BA0?

grts

So if I read it right your last program should work (FS04)?

Many thanks , I will try it out on the field.

grtz , stephan.