Unstable Power for Xe light?

[EricV]

I have a light source using an Xe arc lamp. Our customers have reported a 'flicker' but we can't duplicate it ourselves. Based on the best information I have from the field, this does not occur until after the unit has been in use for 2-4 hours. It apparently is transitory, because we can't see it after the appropriate run time.

My assumption is that there is some instability in the power consuption. The power supply is supposed to be constant current. I do see the voltage constantly vary. Not a lot, but it's very noticable. Kind of looks like line noise. Assuming that the current is steady, what would cause the voltage/power consuption to vary?

Any suggestions as to how to take meaningful measurements? I've got output voltage from the powersupply and temps at the p/s heat sink, the lamp heat sink, and ambient. I see some corellations, but nothing that seems big enough or rapid enough to create a visible flicker.

Any ideas?

 

[dpc]

I suspect the problem may be in the arc lamp. Variations in arc impedance would cause the "constant current" source to vary the output voltage to maintain the current. I would guess that ambient temperature variations could have a role.

Maybe this is a result of the lamp going through some transitory phase prior to reaching a more stable steady-state condition.

 

[EricV]

I did consider a temperature issue with the lamp and/or power supply. It still makes sense, but as this doesn't happen until a couple hours after ignition, it seems a little week. The lamp housing plugs into jacks, is it possible that there is a heat issue there? I can't readily measure the temp there, and I have considered that whatever heat is there, while hot at the point, does not cause create enough energy to be obvious once it conducts into the lamp heat sink.

In general, the arc gap itself shouldn't be susceptable to temp should it?

 

[Aranrhod]

Is this a Xe or Xe/Hg lamp? There are both. I suspect the latter have a shorter lifetime and it may be it needs replacing. If this is so do it soon. If they burst (I believe they are at 200 atmospheres inside) you get a hell of a mess.