Doug, This is only a part response (addition) to your query.
>> It would seem that a white body would be more translucent and you >> risk falsely triggering the transistor. Osram produce a white (SFH421) and black (SFH4271) infrared emitter specifically addressing this issue of translucency. I have worked with both devices and can confirm that the side emissions through the white plastic is not insignificant. There is next to no side emission through the black plastic. I would hazard a guess that the actual optical barrier used in optocouplers is designed for purpose and selection of wavelength gives some additional immunity. Rgds - Chris From: [email protected] [mailto:[email protected]]On Behalf Of Powell, Doug Sent: 31 May 2006 18:03 To: [email protected] Subject: Why are some optocouplers white and some black? This is obviously a trivia question but I think is related to product safety. My recollection is that early on, some manufacturers designated white body optocouplers as the only type that had certain attributes, like agency approvals. It would seem that a white body would be more translucent and you risk falsely triggering the transistor. -Doug Doug Powell Advanced Energy Industries Inc. Fort Collins, Colorado USA - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
