[rollei_list] Re: OT? Selenium in the cold
- From: bigler@xxxxxxxx
- To: rollei_list@xxxxxxxxxxxxx
- Date: Thu, 15 Dec 2005 09:13:54 +0100 (CET)
> No doubt subject already exhaustively covered, but with temperature
> in the teens here (NYC), is my Weston Master II going to be
> affected? John Wilton ragarecords.com/photo
I have used Rollei-Gossen built-in TLR selenium meters down to the
teens Farenheit (between -10 C and 0 C) without any noticeable
problem.
A more scientific answer is given by Megatron, UK, the present (but
for how long time in the future ??) manufacturer of the Weston
Euro-master and still (as of Dec. 2005 and according to their web site
to date) maintaining a range of selenium photo-cells
http://www.megatron.co.uk/selenium/index.html
Megatron quotes the value of -0.1% per degree C, which is the
temperature coefficient for the output current scale factor when a
certain type of selenium cell is used delivering current connected to
a low load resistance. It means that if we start with a reference
value of 100 current units at room temperature (20 deg C, 68 F) we
should expect an output of 96 (-40x0.1%) at -20 deg C (64F). Those
figures reasonably support the idea that in practice we do not have to
care so much for the effect of cold on a selenium exposure meter.
--
Emmanuel BIGLER
<bigler@xxxxxxxx>
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