Re: Calibrating thermometers/measuring light levels

From: Chris Teichreb (
Date: Tue Jan 05 1999 - 13:26:58 PST

Date: Tue, 5 Jan 1999 13:26:58 -0800 (PST)
From: Chris Teichreb <>
Message-Id: <aabcdefg27$foo@default>
Subject: Re: Calibrating thermometers/measuring light levels

Hi Andy,

> I have recently bought a couple of cheap max-min thermometers from a
> local store. I put them next to my old thermometer for a weekend.
> All 3 were close (+/-1degree C) on the min temperature, but differed
> by 10 degrees C on the max. Now I don't know which if any of them to
> believe.
> I suppose I can check the lower end of the temperature
> range by putting them in the fridge or ice/water, but does anyone
> know of an easy way of checking them in the range 20-30 degrees C?

        What's the local temp up to in your region? Is it possible to
stick them all outside and then compare to readings at your local
meteorological station?

> I've recently moved a tank into my office, in the belief that it
> would get plenty of light. Well it seems I was wrong, and although I
> was getting sun a few weeks ago now that its mid summer here
> I'm getting little direct light. Is there any way to measure how
> much total light a tank gets over a day, and compare
> that with an "ideal" amount of light? Or should I just assume the more
> light the better and put a fluorescent of some sort on the tank?

        There are ways of measuring cumulative incoming radiation, but
most involve costly equipment. One way is to use the f-stop reading on a
normal 35mm camera which can be related to incoming foot candles (ie:
visible light radiation). I don't have the details handy, but I do
remember posting something about this about a year ago. Anyways, take
readings every hour or so and average them to get your average incoming

        For simplicity's sake, I'd personally put a fluorescent strip over
if it looks like the plants are suffering.

> Thanks for any ideas/comments
> Andy in NZ - no snow, lots of sun, and a 5.2 on the Richter scale
> last week

Happy growing,


Chris Teichreb
Department of Biological Sciences
Simon Fraser University
Burnaby, B.C.

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