I would agree with George’s numbers. Some of our smaller enclosures don’t have
much thermal mass or internal heating. With the crazy weather extremes, we
could conceivably get down to –25F inside the box for a day, especially the
ones we purposely put on the north side of a grain bin to shield them from the
summer sun.
My question would be, what happens if it gets that cold? Lose some data? Lose
the firmware? Permanently damage the device? I could live with some data loss
as a result of a record temperature day. But I wouldn’t want to go out and
replace a failed unit when it’s that cold.
From: George Skorup
Sent: Monday, May 18, 2015 9:32 PM
To: af@afmug.com
Subject: Re: [AFMUG] Enclosure low temperature
This winter was pretty cold. For about a week straight in the middle of January
and again in February, I had a few base units reporting under 0F every night.
And I know the outside air temp was -20 to -25F. Obviously take the base unit's
temp reading with a grain of salt because it's clearly generating some internal
heat. I would bet inside the enclosures it was easily -15F. But I think your
-13F is probably OK.
On 5/18/2015 9:09 PM, Forrest Christian (List Account) wrote:
What is the lowest temperature that each of you would normally expect to see
in your enclosures?
The reason I'm asking is that I'm in the process of developing up a few new
products.
To date, all of the packetflux products are designed with components rated
-40 to +85C (I.E way cold to way hot). I'd like to retain this rating, but
I'm running into a minor snag:
For storage, I'm planning on integrating a SD card (probably microSD) in a
socket. I only need a GB or so, and SD card memory is inexpensive at that
range.
Unfortunately, all the reasonably priced SD cards are only rated down to
about -25C or -13F. which are about ~$3 in qty. "Industrial temperature
range" ones which are good down to -40C/F are available but they add at least
$30 to the cost for non-name brand, and even more for known brands. When
you're talking about a $100 end-user price, a $30 1GB SD card seems excessive -
and probably isn't even possible if I want to meet the $100 price with some
margin.
So, I'm currently playing the 'what options do I have' game. I hate to ship
a product only rated down to -25C/-13F, but I know for at least a large chunk
of my customer base they never see below this temperature, especially when you
add a watt of power dissipation in the case with the device. Which leads me
back to my original question: What's the lowest temperature most people would
expect to see inside their enclosures.
--
Forrest Christian CEO, PacketFlux Technologies, Inc.
Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602
forre...@imach.com | http://www.packetflux.com
