--- In Jeff Cunningham <> wrote:
>
> Yan Seiner wrote:
> >
> > Does anyone have any suggestions for a cheap thermocouple?
> >
> > I am looking for something that can be put into a small animal
> > environment (cage or tank) so it has to be low voltage and visually
> > unobtrusive; ideally something like the stick-on strain gauges that I
> > can run DC voltage through, and stick on to some out-of-sight portion
> > of the tank.
> >
> > My plan is to run it into the A/D on one of these boards, and control
> > heaters based on the input.
> >
> > I'm coming up dry with Google; I don't need/want a large, industrial
> > unit. I need something a homeowner/pet owner wouldn't notice.
> >
> > --Yan
> >
> What about something like an LM34? Its a 3-terminal temperature sensor
> that takes a 5v supply and outputs millivolts proportional to either F
> or C (there's one for each). Use the A/D to convert.
>
> http://www.makingthings.com/resources/datasheets/acc_tmp_001.pdf
Thanks everyone, I think I'll take Jeff's suggestion as I have A/D on
board and an LM34 looks like the simplest thing to do....
So now a question for all the hardware designers out there:
The document that Jeff quoted shows two ways to wire a three-wire
setup, both on page 7. I can't quite figure out what the difference
is, which one I should use, and why there are 2 resistors in parallel,
one 499 1% and the other 22K 5%.... Are they just trying to adjust
the range of the sensor with the 22K resistor?
What I have is 12 bit A/D that is currently set up for 0-10V; I can
reduce that down to 0-3.3 if need be. I need to measure normal room
temps; between 60 deg. F and 110 deg. F to an accuracy of about a degree.
The sensors will be powered from the TS7300 5v supply. It will be
remotely mounted (up to 10') in a low-noise environment. I have
shielded twisted pair available which I'd like to use.
Could someone give me clue?
Thanks,
--Yan
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