Stefan, maybe i have not made myself clear. My primary goal is to develop a system for a damaged plant that is inoperable. The reason i have ample time on hand is due to the fact that the client is getting his production on another plant of the same category that is not damaged.

Now since the production is going on (on the other plant), the client has asked me to design a system for the dead plant, but in a better way, with possibly more (or less) features that the previous automation system did not provide. In other words, i have got a system to play around with and experiment.

I do not have a problem with the PC Software, or as you might call it - HMI, and the digital part of the control system. Practically, as of now, i have already developed a test system that is working satisfactorily on one of the weighing hoppers (and the associated 4x silos) of the dead plant. This does not include weighing, so i have tested the IOs and operations of vibrators and Pneumatic cylinders for gates.

For the weighing, I was initially of the view to just put in a 18 or 20 bit generic ADC (much like the ones in PLCs) on the control system and use the existing Summing amps from the previous system. Later i found out these summing amps had developed faults in them, some were working OK and some were having problems.

This brought an idea to try and experiment designing such a summing amp, but modular in nature. I have already explained the benefits of the modular approach, irrespective of which strategy in development is used. I was thinking if this can be done, then provided the results are good, i could replace the summing modules on the other running plant with these modular ones for better performance.

Also, if in future, they want to migrate to this custom solution for their presently running plant (based on PLC), then atleast the summing amps would be one less item to change. all that would need to be changed is the PLC & HMI with my control system and PC software.

all this, is only possible if my control system accepts a standard (05V or 0-10V) output coming from a summing amp, whether it is a modular amp of my design OR an off-the-shelf product.

This is why initially i was inclined on following this path for designing a summing amp completely in the analogue domain. However, now i am also considering the options that many people have mentioned here. Ofcourse, both designs have their own Pros and Cons, depends on where you look at them from.


IF i develop a completely active Summing amp or just amplifier with on-board ADC and uC, then i will be able to run my custom developed system fine, BUT incase even though my custom system will have no problems in running on it,