Hi Kiss,
I will have a look at that, thanks.
Ok, I haven't allowed for any Hysteresis as yet due to the fact that the Manometer was telling me it was turbulent flow at the Tap like I mentioned before.
I don't know much about electronics etc but I actually do know quite a bit about dynamic airflow having worked with this since childhood.
I could read manometers & dynamic airflow, & use Lathes & Mills etc 35 years before I learnt how to read & write.
I know there will have to be some cancelling made as well but I wanted to fix the major cause & not remedy the problem so to speak, this is the way I tackle engineering, especially engines.
If I had of canceled out the fluctuation in the sketch first I would have in effect cancelled out the issue of turbulent flow at the Tap.
I have seen expensive test benches that have cancelled out all manner of things we need to read.
I made a laminar flow element, connected it up & there is now only a minor variation hardly noticeable maybe around 2mm of water, very good.
I have attached an Excel graph of the PID working, no particular voltages set in the sketch as yet.
There is a time stamp on the bottom & you will see that due to the plenum the settling time is very long, but that's the plenums effect. You will notice the table top on the overshoot, this is how long the plenum takes to stabilize.
Obviously the area under the curve needs to be a lot smaller, opposite to engines actually but the PID is working, you will see a step in the setpoint voltage but that was me with the switch on the wrong notch, not easy for me to dial things quickly now, hence the need for automation?
I will now try with the plenum removed to get some response & then I will tackle the hysteresis if it is a problem.
All looking ok at the moment, yes I will now put the correct values in the sketch on the graphs but I just wanted to get it working first, no good putting numbers to something that doesn't work.
Cheers