A cement factory approached me via a software company, this SW company cheif knows me as a electronic circuit designer. Long tiem back we worked together for some project where he did the software and I designed the required logic circuits.

At cement factory they have very old control panel, where they have sensors producing current(I) output which shown on analogue (amp) meteres. The operator take those readings, do some calculation and determine the action to be done in order to maintain the throughput and quality of cement materials. This is quite time taking, and since all this calculation is manualy done, the chances of errors are more. Now they want all these to be done electronically. Their instrumentation department have given me the sensors output and the calculation algoritham what they have adopted.

They receive 3 signals in Current form. from (4mA to 20mA) 4mA means "0" and 20mA means "100d". They also add a constant which is equal to 18.25mA. There is some multiplication and division, and result should show as 3 whole numbers digits on 7 segment LED display.
Except analog section all remaining math is so easy, and can be implemented in minutes. A to D conversion is some how new to me. So I have to practice it.

They want me to design, fabricate and incapsulate it in a small box, which they will fix inside their wall mounted panel board. I also have to generate a constant 18.25mA current source within the proposed circuit.

I have quoted them US$1400.00 for total project. Within this around 30% commision is to be given to sw company who brought this project to me. since it is my (re)start, I am not considering too much profit, but at the same time I want to be fair with my efforts and time.

As Jay described, I do not know if the same technic can be offered to other cement factories. So I have to consider it "the only" application.

Jay, please guide me (and others like me) on this.

Thanks

Rauf