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Author:  Brian [ Fri Jan 29, 2016 1:15 am ]
Post subject:  Re: refractometers

Michael P, thanks a watt.

A good band pass filter will block all light outside a 10 nm range, so a good yellow filter will block all but the 585 - 595 nm wavelengths. The narrower the wavelength range of the light source, the sharper the definition between light and shadow on the refractometer (as long as you don't have to worry about speckle, as previously mentioned).

A 20 W SOX is quite sufficient for RI measurements. While that doesn't sound like much input power, and most of that power is heating the lamp enough to keep the sodium vapor from condensing, this is where sodium's conversion efficiency really shines.

Author:  G4Lab [ Sun Apr 10, 2016 6:36 pm ]
Post subject:  Re: refractometers

SOX 18 or 20 are the only ones even remotely useful because of the aspect ratios of the bigger wattages. They are all the same diameter and have U shaped internal tubes and the wattage is a function of the lenght of the unit,)
Also in the not too distance future SOX lamps are sceduled to be discontinued because LEDs are taking over everything so stock up.
The lamp life of SOX series is very long, much longer than any of the previous sodium lamps that have been made for laboratory use.

If you start using an actual sodium lamp for refractometery you won't want to go back. Because you are looking at a sub nanometer spaced pair of lines it looks like one line and the RI shadow line is much sharper than any other method. I have a bunch of interference filters and they are sharper than the Wratten 23A but not as sharp as the real thing.

Yellow LEDs have a big spectral spread and without additional filtering are only a little sharper than White light.

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