Hello Mr. yzeeir yzeeir,

For a kick ass data logger using a PIC 16F84 and DS1721 featuring an RS232 interface, packaged in a sturdy case visit the following web site.

http://www.geocities.com/SiliconVa...logger.htm

I have used this circuit on container cargoes to measure the temperature inside. When the container arrives in port it is downloaded into a PC and the information is downloaded to the shipper via the Internet to show the temperature inside container while it was in transit. They usually use this information to verify the temperature was correct thru out the transit. Should that not be the case they usually file an insurance claim for the value of the cargo.

The circuit performs well in very cold environments.

The circuit performs well off of 4 AA batteries for periods up to two years.

Good luck,

Charles Bannister