[Weather] Temperature Readings Too High

[Seth Cohen]

Hi All,

I'm new to the list and 1-Wire in general, so try to go easy on me.  First
I'll give a little background on the hardware I'm using.

I'm in the process of assembling a 1-Wire weather station and am testing it
"on the bench" before setting it up outside.  I've been building it up one
piece at a time.  I have an AAG V3 weather anemometer, Hobby Boards
temperature and humidity sensor, and a Hobby Boards barometer.  I just added
the barometer over the weekend.  Everything is daisy-chained using parasitic
power.  The barometer has its own power supply.  Just for convenience, I
added the barometer to the end of the daisy chain, just after the
humidity/temp sensor using a pre-made CAT-5 network cable.  In my final
installation, the barometer will be located inside at the start of the daisy
chain.

As soon as I added the barometer (and associated power supply), the
temperature readings on the humidity/temp sensor increased by about 5
degrees.  If I removed the barometer, the temperature readings would very
slowly drop back to the correct temperature.  Looking at the schematic, I
see that the barometer shares its 14 volt power on pins 7 and 8 of the
cable.  I assumed that this was the reason for the increase in temperature.
I made a short cable with only pins 4 and 5 connected to try and verify my
theory.  Using that cable in place of the network cable the temperature
readings have been fine, which seems to corroborate my theory that the power
on pins 7 and 8 was causing some heating on the humidity/temp board.

Has anybody else had a similar experience?  If I decide to not use parasitic
power later on, is there a solution to this problem?

Thanks for your help and sorry for the long explanation,
Seth

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