Re: [ATM] LED's and Diode Electronics

["Richard Schwartz" <richas@earthlink.net>]

Has anybody heard of using LED's for light sensors?    How does that work?

----- Original Message ----- 
From: "Dominic-Luc Webb" <dlwebb@canit.se>
To: "Mark Holm" <mdholm@telerama.com>
Cc: <atm@atmlist.net>
Sent: Wednesday, June 22, 2005 3:08 AM
Subject: Re: [ATM] LED's and Diode Electronics


> On Tue, 21 Jun 2005, Mark Holm wrote:
> 
> > > P21 tubes
> >
> > Is/wasn't the P21 a photomultiplier?
> 
> Specifically, it was the RCA (Now Burle) 1P21. This was used from
> about late 1940's to characterize UBV system. It was surpassed by
> the RCA 931A and finally the RCA 931B. By all accounts, the 931B
> was superior in terms of lower noise, etc. These are all side window
> types. Most companies that produce these no longer list side tube
> types at all on their web pages. I suspect a trend towards end window
> types. As compared to a CMOS or CCD, these have peak sensitivity
> at about 350-400 nm and are quite responsive to UV. Discrete single
> photon counting is possible. There is another PMT that also has good
> a good near IR response the that is an end Window type (EMI makes it,
> but do not rememver number, EMI9451 rings a bell). I think there are
> some people around currently using this for pulse counting UBVRI.
> 
> I presently experiment with the 931A and 931B, which I can get on
> Ebay for a few bucks. I am interested in scanning to get limited
> spatial info, like repetetive cycling between a few nearby stars.
> 
> Dominic-Luc Webb
> 
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