1.In a tank-A there is sludge in the bottom, above water and on top of it oil (3layers). I want to put a sensor (interface meter) in the bottom part which should be able to sense whether it is sludge or water or oil and drain to the different tanks based on the medium. Is this kind of sensor/instrument /meter available. if so please give details.

2. Is it possible the same instrument can measure level also?

Please help to clarify. Thanks!

 

There are a few companies offering solutions for your application. Here is a link to one of them:
http://www.mtssensors.com/products/liquid-level-transmitters/RefineME/index.html

If you choose a level sensor with Modbus RTU, you can use a meter/controller to perform the draining operations. Here is a link to a video that you may find useful:

https://www.predig.com/video/super-snooper-videos

I hope this helps.

JUmana