Datalogging thermometer recommendations.

[Vgkid]

As the title suggest post your data logging thermometer reccomendations.
What i need is one that uses an external temperature sensor. It will be subjected to temps from -20 to 100C.
USB connectivity is preferred, and more than 1 chanel would be nice(2+ would be better).
BUT it must be cheap.
Not looking for real high accuracy.

[biot]

Let me warn you about the UNI-T UT325: does everything you describe and inexpensive, BUT it only ever sends out data about one of its two channels -- big firmware screwup, since both are shown on  the display just  fine.

[radhaz]

There's a number of China usb data loggng thermometers on ebay cheap.

[TSL]

+1 radhaz

I've used one of these to track a misbehaving lab aircon

http://www.ebay.com/itm/BTHP02-2-Chs-Humidity-Temperature-Dew-Point-Data-Logger-USB-64K-32-000-readings-/281703381613

Stick it on the wall for a month and collect and plot later.

[AndyC_772]

Amprobe TMD-56

http://www.amprobe.com/Amprobe/usen/HVAC-Tools/Thermocouple-Thermometers/AMP-TMD-56.htm?PID=73414

[Rick Law]

If you want to make one, an Arduino with the LM35z from TI.

The TI LM35z is -55C to 150C with "typical accuracy" of 1/4C according to their datasheet.

This Arduino+LM35z solution works rather well for me, but I have not exposed the Arduino part to -20C.  I use a meter-long wire and stick only the LM35z part into the outside environment.