chuck@mitlns.mit.edu (09/12/90)
-Message-Text-Follows- In article <4092@disk.UUCP>, stevenw@disk.UUCP (Steven Weller) writes... > > >I would like to make a UV light detector, but do not know > > a) what device I should use to detect UV light, and > > b) how to use it to achieve a meaningful intensity reading. > >Any suggestions are welcome. Please post or email. As long as you have reasonable intenisties a pin diode will work fine, BUT, you need one that is not covered or has a quartz window. the standard epoxy or glass windows won't work. You may need another diode with a normal window to measure the non-uv light so you can subtract. Hammatsu is one company that specializes in these kind of detectors. For a once only deal I've cut the tops off of metal can detectors in a lathe. Works fine as long as they are in a relatively clean enviorment for a reasonable amount of time. You have a LOT more problems with leakage current with exposed detectors, they can work fine for months and suddenly punt. Chuck@mitlns.mit.edu
larry@kitty.UUCP (Larry Lippman) (09/13/90)
In article <4092@disk.UUCP>, stevenw@disk.UUCP (Steven Weller) writes: > I would like to make a UV light detector, but do not know > a) what device I should use to detect UV light, and I assume that you would like to make a quantitative measurement of some sort, and not just detect the presence or absence of a UV radiation source. The first question you must answer is whether you will be measuring the intensity of *just* UV radiation, or will here be visible and infrared radiation also present. In the case of, say, a spectrophotometer, the light being measured is reasonably monochromatic and is shielded from any other radiation source. If you are measuring, say, the UV from a UV lamp in the presence of room illumination you will require a filter to exclude wavelengths longer than those of UV - unless, of course, the UV radiation is orders of magnitude greater than ambient illumination. For general purpose use, various glass types of glass bandpass filters are available from such vendors as Schott. Be aware, however, that some glass bandpass filters intended for UV tranmission *also* have some transmission in the red region. I have learned this fact The Hard Way. :-) For specific wavelengths, narrow and accurate metal-dielectric interference filters are available. Once you have addressed the filter issue, you can then select a photodetector. There are many detector methodologies available, but the three most common are: (1) Vacuum photodiodes, a photoemissive two-element tube requiring an excitation voltage of between 50 and 150 volts. Vacuum photodiodes are available with useful detection at wavelengths as low as 120 nm. With this type of detector there is a direct relationship between current and watts of irradiated energy. (2) Photomultiplier tubes, for applications where sensitivity greater than vacuum photodiodes are required. Utilizes an excitation voltage of typically 1,000 volts. (3) Solid-state photodiodes, generally less sensitivity than the above two devices, but more rugged, compact and easier to use. Solid-state photodiodes may be operated in either photovoltaic mode for maximum sensitivity, or in photoconductive mode for maximum linearity. > b) how to use it to achieve a meaningful intensity reading. If you build a device, the easiest way to calibrate it is to borrow a UV radiometer of known accuracy, such as one manufactured by International Light. Larry Lippman @ Recognition Research Corp. "Have you hugged your cat today?" VOICE: 716/688-1231 {boulder, rutgers, watmath}!ub!kitty!larry FAX: 716/741-9635 {utzoo, uunet}!/ \aerion!larry
commgrp@silver.ucs.indiana.edu (BACS Data Communications Group) (09/14/90)
In article <4092@disk.UUCP>, stevenw@disk.UUCP (Steven Weller) writes: > I would like to make a UV light detector, but do not know > a) what device I should use to detect UV light, and See the premiere issue of _Science Probe_ magazine (Sept. '90; should be on newsstands soon) for a review of Casio's ultraviolet-sensing wristwatch. See also the "Amateur Scientist" column in _Scientific American_, one of the last four issues, for an excellent article on measuring UV. -- Frank Reid reid@ucs.indiana.edu