On 4/16/2011 9:26 AM, Karl Townsend wrote:
I built a serial port temp. sensor years ago based on this fella's
work:
http://quozl.netrek.org/ts/

And just bought kit 145 from carl's electronics:
http://www.kitsrus.com/pdf/k145.pdf

The unit uses DS1820 temp sensors and connects to the pc serial port.
There is a fifty foot run from the computer to the sensor.

My better half made me quit using it because of AM radio interference.
There is a constant beep beep beep.

I'm once again in need of 24 X 7 temp. logging. Is there an easy way
to salvage this unit? Or am I better off to just start over with some
sort of analog unit?

Karl


Start with the basics. Is the cable shielded with the shields
terminated? You should be running shielded twisted pair, and the cable
signal lines should be terminated at both ends. Are the circuit boards
in a grounded metal enclosure? If the system is shielded, the next step
will be to wrap a few turns of the cables around a ferrite attenuator
core, as Jim suggests. If it were in my heart and lung machine I would
add .1uF monolythic ceramic capacitors to the output of the DTS line at
the computer and the input of the voltage regulator on the board.
Separation of the data cable and the AM antenna will help. Running the
cable close to the ground or in metallic conduit will help. An external
AM antenna for the radio (away from the data line) will help.

Kevin Gallimore