Calibration error DU 640
I'm trying to calibrate, and an error message pops up saying it failed "zero order". What does that mean?
I've been seeing this on my DU650. It could mean the UV lamp is old and not getting enough power so the cal sequence can't find the peaks. In my case I seem to have a bad "purple" filter (partly frosted) on the filter wheel which causes the same thing. See my other post for interesting other things like melted goo on the mainbaord.
Zero order is white light. If it happens when you are calibrating then replace the UV lamp. If it is happening during the initial start up then it is probably the visible lamp.
I think the wavelength calibration is only using the 656.1nm peak from the UV deuterium lamp, so why would the white lamp come into play?
I mis-spoke a little bit, I'll blame it on a long day.
When you do a calibration, the first thing it does is go to 0nm (white light), if it can't find it or if it is dim you will get the Zero Order error.
I would start by replacing the visible lamp and peaking it.
My understanding, "zero order", first order, second order and thired order is related to getting the mathematical drivitive of a cerve
As a previous post stated, zero order refers to pure white light at "zero" nanometers as far as the spectrophotometer is concerned. It has nothing to do with a mathematical curve. The spectrophotometer scans back and forth around zero nanometers looking for the white light at the exit slit of the optical bench. If it does not find it, you will get a zero order failure. As Craig said, if you get this error, start by replacing the visible lamp and DO NOT use an off the shelf lamp. Most commercially available halogen lamps have a coating on them to protect consumers from any UV light being generated by the lamp and yes, a visible halogen bulb does actually throw off some UV energy. The lamps that Beckman Coulter uses in their specs do not have this coating and that is the type of lamp that you need to use. Hope this helps.
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Please post any pictures or journal entries you have on this site. I do not click on links that I have no idea where I might be going. This is for the security of my computers.
I will also assume that there is nothing in the sample cell holder when you are trying to calibrate your spec. Also, if you are using a microcuvette holder then you should remove it from the spec as it may clip the white light too much.
RE: use of of the shelf lamp vs. Beckman Lamp
I recently purchased official Beckman 514259 lamps (12V 20W) (for highly inflated prices) and found that the little brown envelopes (marked PN; 514259 Rev. AA) contained a lamp which was marked on the base as Osram 64258 and in the same white plastic bubble package as is in the Osram supplied box for the same lamp. From this I conclude that the lamp from Beckman is nothing special.
I do see that Osram has some info on the special quartz they use, which blocks some of the short UV.
http://www.osram.ec/osram_ec/Servicios_y_herramientas/Training_%26_Knowledge/FAQ/Environment/index.html#answ21 (from Osram site); UV filter technology Question Why does OSRAM use UV filter technology in halogen lamps to protect the environment and our health? Answer In addition to light, halogen lamps emit ultraviolet radiation (rays). Quartz glass used for conventional lamps allows these UV rays to freely pass through the bulb. In order to prevent this, OSRAM is the first lamp manufacturer to use UV filter technology for its entire range of halogen lamps. OSRAM halogen lamps are made of quartz glass that is doped, meaning that it has been enriched with substances that absorb UV rays. This significantly reduces the amount of unwanted UV rays in the light. OSRAM UV filter technology is highly effective in preventing UV-B and UV-C rays from penetrating the glass. These high-energy rays can cause sunburn and conjunctivitis. Only half of the low-energy UV-A rays go through the glass. Another advantage of doped glass is that it reduces fading effects on textiles due to UV rays. ------------------------------------- Looks like it would be nice it there were another source of bulbs that did not filter the UV!
In addition, some of the "legs" on off the shelf lamps are just a bit long. If you use a "store bought" lamp and can't get enough energy, try clipping a 1/2mm off both legs with a wire cutters. One of the main reasons the OEM Beckman bulbs cost more is each one is individually checked for leg length and height of the filament. An off the shelf bulb can work just fine but it might take 15min+ to peak it to proper out put (This is the voice of experience. I was a Beckman Field service tech for 10 years.)
Thanks for clarifying the WHY about the Beckman visible lamps. I quite frankly forgot about the leg length issue and the element height issue too. The unfortunate thing about the operator's manual is that it only tells the customer about using the little tool to adjust for maximum energy when there is also usually the need to adjust the vertical position to achieve the best results.
Myself, I retired after almost 33 years and knowing how things have changed makes me thankful that I'm no longer working for BCI/ Danaher.
All the info on this thread is excellent but let me throw just a bit more out. Remember that all specs are not just pushing a bundle of light through a slit. They are carefully pushing a focused image of the lamp filament through the slit. That is why the filiment height is an important part of peaking your source. If you are holding a Beckman OEM bulb in front of you with the "legs" down, you will note that the filament is HORIZONTAL. Most off the shelf bulbs you can buy in a store have a VERTICAL filament. Obviously the image of a vertical filament will project 90 degrees to the shape of the spec's exit slit and will have only a tiny amount of energy at the detector.
The LARGE majority of light from the visible lamp ends up in the zero -order white light beam. This means that, if the lamp lights at all, you will not get a zero-order error. If you do, something is blocking the beam or your lamp lamp is WAY out of position (unlikely if it was previously working).
When you change a working but old bulb with a fresh one, first tell the spec to go to 0 wavelength, then change the bulb. This will make peaking the new bulb MUCH easier.
At start up, the spec rotates the diffraction grating (a concave mirror with a holographic pattern on it) to where it thinks the zero-order white light image should be. When the white light image of the filament goes through slit, the spec's computer moves the image of the filament back and forth across the slit until it finds the very edge of the image. It then drops a didymium filter into the beam and steps off (this is a very precise stepper motor driving things) the correct number of steps to see if the output peak for the filter is where it is supposed to be. If it finds it, the spec is happy and start-up is done. If it doesn't find the didymium peak, you probably need to call the service tech. All the moving parts of the calibration/grating drive are run by plastic coated steel fishing line (really!). If the plastic coating gets worn, the fishing line cable will slip and you lose calibration. Replacing it your self would be a very un-fun job.