From Earlham CS Department
RTP - Ruggedized Wide Range Temperature Probe
- The 85C response is an error indication from the sensor that means that the temperature conversion was not properly finished. This is usually due to the +5v pin on a DS18S20 not being tied to GND (which puts the sensor into parasite power mode). The other 2 cases are if it doesn't get enough power during the conversion, either due to a under-powered serial port or not enough time to finish the conversion. In digitemp you can extend the conversion time by passing -r 2000 to wait 2 seconds instead of the default 1 second. [Link]
- Raising digitemp's read delay (-r) to 3000ms fixed the 180F error for me (copelco).