Olis Modernized DW-2 Dual Wavelength Spectrophotometer Aminco DW2

Description

Olis Modernized DW-2 Dual Wavelength Spectrophotometer Aminco DW2
Olis Modernized DW-2 Dual Wavelength Spectrophotometer Aminco DW2
This equipment is in good condition, with some scratches in the white paint. Without software I can’t fully test it, although the visible light, UV light, and beam splitter all work.
Dual Wavelength Spectroscopy: Still the Method of Choice for Acquiring Correct Absorbance Readings on Turbid Solutions!
When investigators at the University of Pennsylvania designed an absorbance spectrophotometer which sent two wavelengths of light through one sample, they created a spectrophotometer which investigators working on P450, mitochondria, plant and tissue suspensions, and other particulate samples would trust for decades to produce accurate absorbance readings on scattering samples.
Turbid samples have large to overwhelmingly large backgrounds, which make obtaining accurate absorbance readings very difficult. The more turbid the sample, the more incorrect the answer obtained by an ordinary scanning spectrophotometer will be.
And, one cannot know that the results are incorrect with the ordinary spectrophotometer without further quantitative measurements.
Scatter is a function of 1/λ4, so the deleterious effects of scatter increase dramatically as the wavelength goes towards shorter wavelengths (the UV).
With a highly scattering sample, the measuring light is deflected (scattered) away from the detector, so close positioning of a detector to the sample is critical. Most absorbance spectrophotometers use small face detectors positioned many centimeters from the sample. The DW-2 uses a large face detector a few millimeters from the sample.
However, the “DW-2”gets its name from its more obvious difference from normal spectrophotometers: its use of two monochromators to produce a reference wavelength which is subtracted from the (artificially high) absorbance returned by the sample.
One monochromator is motorized, so that it can scan wavelengths. This “Mono 1” is used to scan the spectrum of interest, i.e., 580-520 nm. “Mono 2” is set to the reference wavelength. When the difference between the returned values is taken, one has a “difference spectrum” which is as close to “correct” as one can obtain from a scattering sample. (One is still contending with two effects: the reference beam is not at the same wavelength as the measuring beam, and, without extraordinary measures, one cannot collect all the scattered light and therefore cannot get a perfect answer.)
When the absorbance value is calculated using the Mono 2 reference, in effect, one produces a “Difference Spectrum.”
Technical Specifications of the Aminco DW-2 and DW-2000
Monochromators:
Holographic, dual gratings, Czerny-Turner mountings with 1200 grooves/mm. Five-phase step motor control with minimum step size of 0.05 nm.
PMT:
Hamamatsu R562HA or equivalent
Wavelength Readability:
< ± 0.05 nm
Wavelength Range:
190 - 900 nm
Wavelength Accuracy:
< ± 0.2 nm
Wavelength Precision:
< ± 0.1 nm
Wavelength Resolution:
< 0.3 nm (measured at the half-peak height of 486 nm deuterium emission line)
Slit Width Range:
< 0.01 nm to 15.0 nm, continuously variable
Stray Light:
at 200 nm: < 0.02%; at 300 nm: < 0.03%; at 700 nm: < 0.01%
Photometric Ranges Absorbance Range:
-3.0 to 3.0 AU;Maximum Sensitivity: 0.001 Au full scale; Baseline Offset: -3.0 to 3.0 AU;
Transmittance Range:
0 to 100%;Maximum Sensitivity: 0 to 0.1% full scale; Baseline Offset: 0 to 100%
Photometric Accuracy Deuterium Lamp Supply:
current-regulated pulse width modulator with full line isolation. Automatic warmup cycle and regulated two-stage DC filament source for use with 10 V filament, 35 watt Hamamatsu deuterium lamps. RMS ripple at 60 Hz: 0.01%; RMS noise at 29 kHz: 0.03%
Tungsten-Iodide Lamp Supply:
High stability linear element regulator with soft-start capability. Voltage sensed regulation. RMS ripple at 60 Hz: 0.008%; RMS noise at <60 Hz: 0.008%
Signal to Noise Ratio:
at 3 nm slit, 450 nm, slow filter; at 0 Å: < ±0.0005 AU; at 2 Å: < ±0.001 AU peak to peak
Photometric Stability:
double beam mode at 550 nm, 3 nm slit; < 0.004 AU/hour
Wavelength Scanning Speed:
0.1 nm/sec to 20 nm/sec
Repetitive Scanning:
Arbitrary number of repetitions
Baseline Flatness:
in double beam mode,< ±0.001 AU throughout the wavelength range, computer corrected
Power Requirements:
120V, 50/60 Hz; 240V, 50/60 Hz; 1000 watts
Dimensions
Length: 44 inches (112 cm); Width: 22 inches (56 cm); Height: 21.5 inches (55 cm);
Weight:
approximately 300 pounds (136 kg)
Frequently asked questions
How are you?
About the same, thanks for asking.
So what's included in your listing?
Everything you see in the pictures and nothing you don't.
What about the white backdrop? Is the white backdrop included?
No.
How about…
No, anything you see reflected in the shiny surfaces is not included either. Sheesh.
Anything else?
I'll throw in a box.
Oh, a smart guy, eh?
In case that's not rhetorical: I'm no expert, and I'm certainly not smart enough to know about everything that passes my way. I do my best to evaluate the things I sell, but often defer to the superior knowledge of the prospective buyer.
Will you ever learn?
Probably not.
What’s with your hair?
Um…wait, what?
What if the item I buy from you doesn't work?
You have 30 days from receipt to return it for a refund if it doesn't do as I describe.
What if I don't like the color?
Then you have 14 days.
If I tell you how crappy and obsolete your item is in a condescending enough tone, will you do me the favor of selling it to me for a fraction of your asking price?
You sure know how to butter a guy up. No.
I didn’t bother to read your description. Can you fill me in on the details?
Sure. Send a stamped self-addressed envelope to: mehoff58, c/o eBay, Internet.
Can I pick up my winnings in person?
I don't know you well enough to know your capabilities.
OK, may I?
Certainly!
I need your item, so lower your price.
Not really a question. Nope, not a question at all.
I bought this gadget from you 5 months ago and just found out it doesn’t work. Will you refund my money?
30 days is my limit. I can’t afford to keep large stores of cash handy for long warranties on used equipment. Besides, I don’t know how you stored it or handled it or if it was damaged in shipping. Anyway, no.
Did I forget anything?
What am I, a mind reader?
Will you discuss these imaginary conversations with your psychiatrist?
The conversations are quite real, it's you who are imaginary.
You just blew my mind.
Who said that?
I live overseas. Will you declare the value as 10% of the selling price?
No, and I’ll tell you why. Consider these three scenarios:
Scenario one: I agree to declare a lower value as a personal favor to you, a complete stranger. A few days after shipping, I get a call from US Customs asking all kinds of questions about the value of the item, to whom I am sending it, etc. I’m not a good liar.
Scenario two: I agree to declare a lower value as a personal favor to you, a complete stranger. The package gets lost in transit. You go through eBay to get all your money back from me. I’m stuck with a paltry settlement from the USPS.
Scenario three: It’s fraud.
I hope this explanation has been helpful.
Have you changed your privacy policy?
Seriously, who said that?
Get images that
make Supersized seem small.
Showcase your items with Auctiva's
Listing Templates!
THE simple solution for eBay sellers.
Track Page Views With
Auctiva's FREE Counter