[time-nuts] cheap USB voltage sensor

[beale]

> Bringing up a question: Does anyone know of a cheap (<$20ish) USB voltage
> sensor (16 bits or better, ideally)..  I can see one of those Atmel USB
> capable micros (like the one on the Arduino Uno) hooked to a dual slope or
> successive approximation ADC.

Doesn't quite meet your price, but there's a 3.3V version of an Arduino called a "JeeNode" designed for sensor work, and there are a number of I2C based sensor plugins for it. For example the "analog plug" based on Microchip MCP3424 with 4 channels of differential inputs at 18 bits.  Jeenode (kit) is $23 and Analog plug (assembled) is $12. It's the standard Arduino architecture, so it is simple to use and (re-)program from your PC via USB, no extra programmer needed. 

http://shop.moderndevice.com/products/jeenode-kit
http://shop.moderndevice.com/products/jeelabs-analog-plug

I have some and they work well. Here's a plot of voltage vs time on an AA battery, showing the 18 bit performance (1 LSB = 15 uV). Noise is generally +/-1 LSB.  https://picasaweb.google.com/lh/photo/q7Lq4oAX_0347S8BO0eHSA

You can plug up to four "analog plugs" directly into the JeeNode (software I2C) and these can actually be daisy-chained as well, with 6 different I2C addresses per I2C chain, for up to 24 total plugs per JeeNode which would be 96 ADC channels. If you are in Europe you can buy hardware direct from the designer at http://jeelabs.com/