Ammeter to measure hotend output?

sinned6915

I am trying to tweak my hotend and PID tuning as a result of reading the wiki description-

https://en.m.wikipedia.org/wiki/PID_controller

So i put a 10A 0-100VDC ammeter inline with the hotend to see what the output was actually doing.

I think that the ammeter is averaging out the PWM signal. So for example, if the display reads 6V on a 24V system, then its at ~25%PWM output?

Is there a way to display the actual PWM output either on DWC or on the PanelDue?

I thought that this was somehow accessible as a data point? How would we read it or graph it?

thanks in advance

sinneD

jens55

Unless you have a meter that reads true RMS (I doubt the one in the picture will do that), your setup will confuse you more than help you.

sinned6915

@jens55 agreed. its a curiosity at best right now.

is the real value for duty cycle available in the data stream somewhere? I would trust that as reliable.

dc42

You can use the M573 command to report the actual heater PWM.

sinned6915

@dc42 said in Ammeter to measure hotend output?:

You can use the M573 command to report the actual heater PWM.

dc42: is that a static call and response? is there any way to make it into a data stream to display on the PanelDue or DWC console?

sinned6915

maybe i should have introduce more to this-

i am getting random 'Heater Fault" reporting.
It does not show up onthe GCode console
the print does not pause either- the heaters are still on and the print is still going.

alt text

the false positive is just as bad as a real one in my mind.

jens55

You might want to try and reboot the Duet - I had random errors like that and they still crop up now and then. Rebooting fixes that for me. There is some flag left over someplace from a previous error that causes the message to pop up ... and I had this happening just now. You can dismiss the warning and carry on but it will pop up again sometime later and only a reboot clears the flag.

dc42

@sinned6915 said in Ammeter to measure hotend output?:

maybe i should have introduce more to this-

i am getting random 'Heater Fault" reporting.
It does not show up onthe GCode console
the print does not pause either- the heaters are still on and the print is still going.

the false positive is just as bad as a real one in my mind.

Have you run M303 heater tuning? https://duet3d.dozuki.com/Wiki/Spurious_heater_faults_and_how_to_avoid_them