ScienceHideout
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UV VIS spectrophotometer lamp alignment
Hello everyone!
I have been looking into buying a spectrophotometer for quite some time now- unfortunately the one that really appeals to me has a lamp alignment
error. Do these errors tend to affect the functionality of the machine? If it does, is it an easy fix?
Thanks a lot,
Dean
hey, if you are reading this, I can't U2U, but you are always welcome to send me an email!
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benzylchloride1
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Lamp alignment errors will decrease the amount of radiation getting to the detector. This will decrease the sensitivity of the instrument, but the
severity of the problem will depend upon how far out of alignment the lamp is. What instrument are you interested in buying, I may have the manual,
and instructions for lamp alignment. Theoretically the lamp is aligned for maximum signal which indicates maximum light throughput. Best wishes with
your purchase.
Amateur NMR spectroscopist
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ScienceHideout
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Benzyl chloride, thank you for your response. I am contacting the owner of the machine and I will certainly think about purchasing it. It is a Milton
Roy Spectronic Genesys 5, I actually dug up a pdf of the manual online, but you seem to have a great knowledge of this type of stuff, so I would
appreciate any insight you can give me about aligning the lamp on this spec. Thanks!
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ScienceHideout
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Ohhh... sorry to double post but I have found out more information about the specific lamp alignment error that the machine receives... The error
says: "Tung. Peak Not Found." What do you think that could mean?
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daragh8008
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It could mean that the tungsten lamp is blown. Uv vis systems usually have a deuterium lamp and tungsten. Deuterium for uv then crosses over to
tungsten for the rest. If the tungsten bulb is gone then it sould be reasonable to replace. ( same can't be said for deuterium bulbs) if the seller is
ok with it he might run a test spectra for you. If its completely flat in the vis/near ir then I would think the bulb is gone. Also on some systems
there is diagnostic software that will tell you more.
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ScienceHideout
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I don't think that the tungsten bulb is blown, because before the machine does a bulb alignment check, it does a tungsten bulb check... According to
the tungsten bulb check, it says OK, but the bulb alignment is where the error is.
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daragh8008
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Does the manual give a proceedure for re aligning the bulb. If so then it could be an easy fix. But if not I would worry that it's a manufacturer
service, and that's sure to be expensive. I've worked with uv vis spectra a good bit and never had an alignment error. May be due to rough moving
knocking off the optics. Does it finish it's test sequence to a useable state or could there be more errors yet to come.
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ScienceHideout
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Yes, the manual says to select a program built into the spectrophotometer for a manual vertical alignment for the tungsten bulb. (Deuterium is
automatic). You just execute the program, open up the hatch, and turn a screw until the number is at its highest point. Is that what the 'peak' is
that it is referring to?
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daragh8008
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I guess It must be referring to the intensity peak so. From what I recall the spectrum of tungsten doesn't have any sharp spectral lines for a
wavelenght calibration. (though you would want to check that for yourself!) had a read through the manual couldn't see any errors mentioned that
matches your error. I guess you could try asking the manufacturer about it? They may be happy to give you a few pointers.
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ScienceHideout
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So... I am now in possession of this machine and there are a couple things that I am trying to figure out...
I got the error, lamp alignment LAN error, tungsten peak not found... etc. So I opened up the cover and unplugged the Deuterium lamp, and the tungsten
lamp is there, but it is so dim (not to mention this weird noise, but I think that is the motor for the mirror to go back and forth). It does look
like light is shining into the monochromator, but just not a lot. THe little mirror goes back and forth no problem. When I power off the unit, the
bulb goes brightly (REALLY brightly) and then it is all black... Very weird. Is there some sort of power-saving feature on the bulb? How much light
does it really need? Should I test it somehow? How do I know that there is not a misalignment somewhere else in the machine?
Thanks soo much... I want to get this think working very badly.
hey, if you are reading this, I can't U2U, but you are always welcome to send me an email!
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ScienceHideout
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Sorry to double post, but I think I know exactly what is wrong... I just don't know how to fix it. Using a multimeter, it appears that only about 1 V
is going to the light bulb, when the bulb says it needs 6 V, therefore the bulb is too dim and the machine doesn't see it... I don't think there is
anything wrong with the power supply... How do I check?
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