This is true presario, and is perfectly adequate for my needs - the circuit needs to trigger an alarm when the ambient temperature falls below zero, and another alarm if the temperature reaches -7 degrees C. So I was going to use a spare indoor thermostat that I make previously, and reprogramme the PIC to suit (saving time and build cost). However, my pride would like me to display the temperature to the same resoultion of 0.1 degree, both in the negative and possitive, the formula used in onewire.bas, gives a resoultion of 0.01 degrees.

I think the best way forward is to try it and see what happens, and look at the contents of the DS18S20 COUNT_REMAIN and COUNT_PER_C registers, with the sensor left in my freezer for an hour or so, with a known accurate thermometer and adjust algorithm accordingly.

many thanks