Are you using the lps physical switch between the measurements? You should be able to leave the current meter connected…
Then test with the switch on and off.
Are you using the lps physical switch between the measurements? You should be able to leave the current meter connected…
Then test with the switch on and off.
So my unit has a window for a switch but I don’t see a switch. I didn’t want to poke anything in there to explore. So to disable P1 I just unconnected the Cat5 cable. And test fired it off the LPS. Not the button on P1.
If M1 is spliced into the cathode lead, then I’d expect its additional resistance to affect the tube current, but not by a lot.
Plus, we’re not dealing with instruments calibrated to NIST standards.
I’m unsure what all this means. Let’s back up and run over it again.
I assumed the meter on the remote display (P1?) always shows the tube current, regardless of the switch position on the power supply that enables the knob.
Is that the case? If so, there’s no need (other than curiosity, which is perfectly valid) to splice M1 into the cathode.
Is M2 the digital meter built into the power supply case?
It looks as though either TEST
button fires the tube at about a third of the maximum current: 7 mA vs 20 mA
I think this means that the power supply delivers about 20 mA:
Turning the knob counterclockwise reduces the current from that value to zero and turning it clockwise does not increase the current beyond the value when the remote display is not connected.
If I have that right, then the knob works pretty much as I expected: it can reduce the current from the maximum value set by the trimpot inside the HV supply, but cannot increase the current beyond that value.
Bonus!
Doesn’t look like it’s got a switch…
Our messages crossed in the ether.
The Cloudray description is light on details, but specifically says the “new version” of the 100 W supply does not have a switch:
You could convince me that’s a switch sticking out in the “new version” photo, but I’m gullible that way.
So it seems you plug in the remote display and It Just Works™.
Learn something new every day.
I think the conclusion still stands: the knob reduces the current from the level set by the power supply’s internal trimpot, but does not increase it.
Correct. Knob always reduces current because I set max current to the max knob setting.
I’ll read your other post tomorrow
Thanks for your thoughts on all this.
If I have this right, you can set any PWM level in LightBurn or the machine console, whereupon the knob can produce any current between that level and zero.
The upper limit would be a PWM setting of 100% (or 99%), which will produce the maximum current set by the trimpot behind the tiny hole in the power supply. That is the same current the supply produces at 100% with the remote display unplugged; I think that’s this condition:
M1 connected and P1 disconnected
Same as above so P1 disconnect equals CW
Full power cut: 20.9
Seems like the knob behaves sensibly, even though I still don’t see much point in using it.