This data logger uses an Arduino, an ibridge keypad ($8,90) and an Nokia 5110 LCD screen ($6,80;iteadstudio). I am writing a library for the keypad and the graph screen to view the measurements. Adding one or more sensors (Analog or I2C) is easy. If powered bij 9V battery it wil be a compact datalogger. In earlier projects i made programs for saving on eprom and/or graph-output to VB on PC, so that will be an option if there is an interest.
The first sotware verion shows "Hello World", then shows which key is pressed (rownr, colomnr), if not row 1 it will draw a sinus until a button on row 1 is pressed (press for about 1 second).
The second version (bridge3) starts with "Datalogger", button 4,1 (row,colom) draws a sinus. After you stop it (button on row 1 or 3,1) you van zoom/reduce or shit up/down with the buttons om row 2.
The same for a measurement on A0, when you use button 4,2 or 4,3 (only with 4,3 it stops after 400 points). Button 4,4 sends the 400 remembered measurements via USB to the PC.
Buttons on row 3 give an interrupt (immediate stop of measurement)
In the software its easy to change, scale, interval of measurement etc., only with more then 400 integers, the Arduino 'forgets' how to show letters on the display
Next version will bring I2C measurements, 3 channels for measurements and easier manipulation of the graph (during measurement?).