I’m looking for a relatively low cost device that can simply record a voltage periodically. I used to have one in college but they don’t seem to exist any more. It seems simple enough to take a microcontroller with an ADC have it record a voltage and write it to an SD card, have jumpers, or a file on the SD card to set the record rate. I almost want to design my own, but I just don’t have the time and it seems like something that should already exist. So many sensors output a voltage it would be so handy to have a small/cheap device that you could hook up and record the reading over time. Anyone know of such a device?
One of these: https://www.sparkfun.com/products/13712 and any Arduino with an ADC will do what you want.
The Sparkfun OpenLog (linked above) is a complete 3.3V Arduino, so if you are handy with a fine tipped soldering pencil, you could attach leads to the ADC pins and take voltage readings using the logger itself. It is a shame that Sparkfun designers did not include a couple of connection points for that purpose.
That approach would also require modifying the OpenLog source code, but it is pretty straightforward. It is possible that someone has already done that, and posted on the web, so check!