This page provides a little more detail on the data logger family that I use. Other logger brands/families may well provide similar capabilities -- I am just passing along some information on the brand I have used and know.
The onset U12, 4 channel data logger (about the size of a matchbox), with 4 temperature sensors hooked up.
In this picture its hooked up to a laptop, but it will log on its own for months at a time with no PC or external power connected.
The new Onset Pendant logger. These are available to log temperature and/or light intensity. The logger is programmed and read out by inserting it into a coupler -- this connects to the USB port on your computer. $40 and up.
This is a very small part of a pretty extensive family of loggers that Onset offers.
While the Onset loggers are a good deal less expensive that loggers of a few years ago, they still stretch the definition of cheap instrumentation. The prices are of this order:
4 channel U12 logger (accepts up to 4 sensors) $90
4 temperature sensors (about $35 each) $140
Software (required) $95 (there may be a less expensive version now)
So, a bit over $300 for a useable system.
Note: Onset has recently added some "starter" systems that package together a logger and software at a bargain price.
These are the pros/cons of the Onset from my knothole:
Good resolution and accuracy
Easy to use
Fairly wide range of sensors, and some support for custom sensors
Works right out of the box with no tinkering, soldering, calibrating, ...
Long term standalone operation on internal battery
Good software for plotting data and combining data of multiple types and from multiple loggers
On the expensive side
Potentially not as flexible as a "roll your own" system
If you the price seems high, and you are electronically inclined, then you might want to look into some of the data logger kits (a couple are listed on the Measurements Page), or a make your own system, such as the one listed from AnotherURL.com. If you want an approach somewhere in the middle, you might take a look at the LabJack logger. The "1-Wire" series of loggers is also popular as a low cost way to data logging.
01/26/06, Updated Oct 10, 2007, November 14, 2008