Hello Jay,
in 1997 I built a outdoor thermometer with a DS1820, Used about
20' of 3 cond. shielded cable to the sensor.It worked good, and I
didnt get around to grounding the shield right away.
After about 1 month we got a lighting hit less than 1000' away
it fried the input pin on the micro.I added a 1K resister in series
with the data line going into the micro and and 2 diodes to
VCC and ground and a 560 uf low esr electrolytic across VCC and ground very close to the diodes. The VCC has a 10 ohm decoupleing
resistor from the +5V supply for the micro, and is for powering the
DS1820. Unbelievably after about another month another close
lightinging hit this time it took out the DS1820 but left the micro
undamaged. I added the same circuit to the DS1820 end of the
line and 3 years and several lightening hits later it still has been
working 24hrs/365 days a year.
Hope this helps . Bruce

to DS1820 >
+5V------10ohm res----------------------------------------VCC>
* *
* diode
560 uf data-----------------1kres----DATA> * diode
GND-------------------*------------------------------------GND>