VULCAN20 wrote:
> We are planning a PIC based controller for a solar water collector.  it 
> will monitor water  temp. at 3 or 4 points and control 2 water pumps for 
> circulating the water.
> We have some NTC 103 thermistors and some solid state relays (3-30V DC 
> in and 40 to240V AC out.
>
> The sensor may be located as far as 100 FT away. and temprange of  32 
> deg to200 deg F( approx 0C to 100C)
>
> What I am looking for from the group is this: 
>  Does anyone have Hands on  experience with temperature control sensors 
> and could recomend a better temperatur sensor.  We would like to imerse 
> it in the water.
>
> For more details please contact off list.
>
> Thank you.
>   
I like the National temp sensors with I2C. One/half degree C or better 
at a very reasonable price.

What I did was to let the sensors drive an PIC10F200 on a tiny (1/2" x 
1/2" sq) PCB. Then obtain the data
then send it serially on one wire (plus pwr/gnd) as slow speed 
manchester data. This way prevents any
data loss, even if the distance is extensive (250' +). I have sent 
manchester data as far as 500' without
loss, by slowing the bit time to bit-bit interval of 20mS.


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