User

The SPEC 200 readout blinks each time that it updates the reading in the Live Display to let you know that it has updated.  At 100%T you should expect a little noise - maybe plus or minus 1%T, depending on the wavelength.  Like any spec with a tungsten lamp it has lots of energy in the middle of the visible but a whole lot less in the UV (where the lamp is weak) and in the NIR (where the silicon in the detector element isn't as sensitive).  It'll tend to be noisier where it has less signal to measure.  1%T at 100%T is next to nothing.  If you flip the instrument into Absorbance mode it should appear a lot more stable.  As you start putting samples into the instrument and getting into the middle of the detector's range the reading should become more stable.  The sweet spot of most detectors is someplace in the middle of the range.

There are some important differences between the old SPEC 20 and the SPEC 200.  The biggest is that because the SPEC 200 uses an array detector you are looking at the output from a really tiny piece of silicon when you do a single wavelength measurement.  In the old SPEC 20, the detector was a few millimeters square so there was more signal by far.  Also, SPEC 200 has a bandwidth specification on <4nm, compared to the barn-door wide 20nm on the SPEC 20.  What you give up in stability through having less energy in each individual reading you get back in excellent wavelength precision, not having to mess about with re-setting 0%T and 100%T every time you change wavelength, and the fact that the thing can scan the entire spectrum in a few seconds, do four point quant rather than just single point and generally looks like it belongs in this century rather than "Back to the Future".

All that said.... if the thing is wandering around by 3 or 4%T or more after letting it warm up for 20 minutes there's probably something wrong with it.  In that case, call Thermo's Tech Support people and see about getting it repaired.

Dear,

If Lamp Testing Failed on Start up, what caused, whereas the lamp is a new one.

BR,

Achmad Kurdi

Hi Achmad,

During start-up all spectrophotometers look for a certain amount of energy to be getting to the detector from the lamp.  If they don't see enough energy to meet this threashold the firmware will complain of a lamp error of some sort because if everything else is okay the most likely cause is that the lamp is either dimming at the end of its life or has already died.

If, however, you have something in the sample compartment that is blocking the beam partially, you often get the same result, so the first thing to do is to check that there's nothing in the sample compartment, and since your SPEC 200 has a removable sample compartment, you also need to make sure that it is seated properly.  The quickest check of this is to simply remove the sample compartment and try starting the instrument.  If the instrument still shows the Lamp Error on start-up....go to the next paragraph.

This is going to sound silly, but do check that the lamp is actually lit by looking in though the grill on the back of the lamp-house.  It is possible that you have a burned out lamp.  Even if the lamp is new, if the glass envelope developed a leak due to stress around the pins when the lamp was inserted, it might have lost its seal and would burn out pretty fast.  If the lamp is lit....go to the next paragraph.

The lamp filament is the first component in the optical system of the spectrophotometer.  It needs to be in the correct position, plus or minus a millimeter or two.  Occasionally it happens that somebody figures out that the spectrophotometer lamp looks exactly like one of the lamps he recently changed on his car, and those cost $2.50 each, rather than $25 each, so he tries the automotive lamp.  Even if the voltage and wattage of the auto lamp are correct, the odds are that the filament is in the wrong position, so you don't get enough light through the optical system and the spectrophotometer gets unhappy.  I'm not suggesting that you did this, but it is worth mentioning, just in case somebody else reading this forum has been considering it.  :-)

Standard disclaimer - the lamp gets very hot when it is on.  Let it cool for at least 20 minutes before touching it, never touch it with a bare hand even when cool (use a cloth or Kimwipe so you don't get skin oils on it) and don't look at it when it is lit as it is also very bright and will hurt your eyes. 

If you have just changed the lamp, the most likely problem is that the lamp is not seated in exactly the same position as when the unit was manufactured and aligned.  Try opening the lamp hatch and re-seating the lamp so that it is in perfectly straight.  Make sure that you thread the thumb-screw on the lamp door correctly (i.e. not cross threaded) and tighten it all the way when you close the door.  If that doesn't fix the problem, try tilting the lamp to the left or right of center about 1mm and then re-starting the instrument.  Moving the lamp up by 1mm is the last thing to try.  Note that the little metal clamp that goes over the top of the lamp doesn't really need to be there if you don't move the instrument around regularly.  Its purpose is to stop the lamp from moving when the instrument is being shipped to you from the factory and/or in teaching lab applications where the instrument gets carried around and stacked upright on a shelf when not in use.  If you never move the thing around you can remove that clamp and stick it in a drawer.

I hope that one of these suggestions will solve your problem.

Dear,   Your expalanation very satisfied for me. Actually, the lamp is okay, and the lamp is a original for this instrument, not lamp of automobile.   The Failed caused the beam setting perfectly inthe center of the lens to the detector. If the beam abit moved, the lamp test  was passed. Could you give suggesstion ? Thanks you.   BR,   Achmad K ----------------- 

Hello Achmad,

How did you move the alignment of the beam to verify that this was the problem?

You put really very helpful information.