Hypersensing questions

snowgoer540 wrote: Ok good! At least we have a solid baseline.

I havent had time today to do any work on the plasma, I was going to use a small wattage resistor as you did here, and not fire the torch. But I think that saves me some testing. Is there a reason you used 22K ohm over the suggested 24K by Peter?

For the hal scope tests you are doing, can you describe exactly what you are doing to test it? I want to make sure I can perform the same tests to reliably test what's going on. I am glad that the resistor takes the sensitivity to a wet torch down. That's a giant step in the right direction in my opinion.

I am still wondering... is that the use case Rod is trying to fix via code, or is he testing something else?

Used a 22KOhm over 24K just because that's what I had. Shouldn't make a big difference except in wattage requirement if you stray too far.

Power = V^2/R so for a 24K resistor at 300V, you get 3.75W required, 4.09W for a 22K

With hal scope I'm running 2 channels. Ohmic-volts on one channel and ohmic-on with the other. Set the trigger based off of ohmic-on and let it capture the data. Or I just keep it on "Rolling" and manually stop the data capture so I can get data before and after the event.

Thank you for the maths! How would one settle on 24K over 10K?

My guess would be that the trade-off is high sensitivity= lower sense current - more susceptible
to leakage from water in torch vs low sensitivity = higher sense current - worse at detecting contact
with dirty surfaces, though this may be improved with a higher sense voltage.

Sorry to sort of but in, but I have been reading through this forum and then many others tonight and there seems to be a lot of negative press around ohmic sensing and water tables. It got me thinking about a whole other way of non contact sensing with say a proximity sensor or some other device completely left of centre. In my research I came across this technology by swift cut. They claim it’s like a feather sense that can sense even the thinnest material and I’d say for 99.99% of cases it would work flawlessly. Could this be a solution or even a technology added into Plasma C to take it to the next level?

Attached is the brochure of the plate sensor and a demo Video , I couldn’t find a good view of it cutting thin material but have seen on Instagram it sensing 1.2mm with no sweat.

If this should have its own topic created let me know and I apologise in advance but I thought most people who would have an interest in this are replying to or viewing this topic.

Ohmic sensing has its limits (eg can't be used on a torch without a separate shield - eg Everlast) In these situations the simplest solution might be to use an air ram with a spring loaded ohmic probe triggered by plasmac.ohmic-enable signal and use ohmic sensing. That keeps it within the current design parameters and eliminates an shorts in the tip from water as its no longer in the circuit. You could use a proximity sensor with this method too I guess but you'd have to look at repeatability of the returned measurement for the chosen prox sensor.

However, if we finish of the experiments here, we will probably have a simple solution that will allow ohmic sensing to be used on water tables reliably where torch design permits its use.

On that note, I think I will put my relay back into the circuit becasue a constant current in the torch tip is probably not good for consumables as some electrolysis may occur... Does anyone have thoughts on that?

rodw wrote: Ohmic sensing has its limits (eg can't be used on a torch without a separate shield - eg Everlast) In these situations the simplest solution might be to use an air ram with a spring loaded ohmic probe triggered by plasmac.ohmic-enable signal and use ohmic sensing. That keeps it within the current design parameters and eliminates an shorts in the tip from water as its no longer in the circuit. You could use a proximity sensor with this method too I guess but you'd have to look at repeatability of the returned measurement for the chosen prox sensor.

Any idea how you’d program in the offset so that the air ram comes down, senses near your pierce position, retracts up and then brings your torch to that position? Like In that swift-cut video? I might make a seperate post on this subject.