Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!usc!rpi!zaphod.mps.ohio-state.edu!sdd.hp.com!hplabs!hpl-opus!hpnmdla!darrylo
From: darrylo@hpnmdla.hp.com (Darryl Okahata)
Newsgroups: comp.sys.handhelds
Subject: Re: Hewlett-Packard LED's
Message-ID: <1570019@hpnmdla.hp.com>
Date: 15 Mar 91 22:26:10 GMT
References: <1991Mar14.154224.19336@en.ecn.purdue.edu>
Organization: HP Network Measurements Div, Santa Rosa, CA
Lines: 32

In comp.sys.handhelds, nichols@en.ecn.purdue.edu (Scott P Nichols) writes:

> Does anyone know the wavelength of the IR LED's that the HP-48SX uses?
> I'm guessing about 806-820 nm, but I'd greatly appreciate an answer from  
> someone who knows exactly.

     I don't know the wavelength of that LED, but the "HP-48SX Technical
Interfacing Guide" contains a schematic that uses either the HP
HEMP-3301 or the NEC SE303A LEDs.  For the HP HEMT-3301 (which I assume
is the about the same as the HEMP-3301 -- or "HEMP" could also be a
typo), the specs are:

Ta=-40 deg C:	Spectral peak @ ~920nm (and is ~1.35 times that of the
					peak at Ta=25 deg C)
		50% of peak @ ~910nm & ~935nm

Ta=25 deg C:	Spectral peak @ 940nm
		50% of peak @ ~920nm & ~960nm

Ta=85 deg C:	Spectral peak @ ~955nm (and is ~0.65 times that of the
					peak at Ta=25 deg C)
		50% of peak @ ~930nm & ~980nm

Note that "Ta" = "ambient temperature".

     -- Darryl Okahata
	UUCP: {hplabs!, hpcea!, hpfcla!} hpnmd!darrylo
	Internet: darrylo%hpnmd@relay.hp.com

DISCLAIMER: this message is the author's personal opinion and does not
constitute the support, opinion or policy of Hewlett-Packard or of the
little green men that have been following him all day.