[time-nuts] cheap USB voltage sensor
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/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] cheap USB voltage sensor
In message 20120113200200.14805.qm...@s421.sureserver.com, =?iso-8859-1?Q?be ale?= writes: 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 Did you try to hold the battery in your hand while you did that ? :-) Be aware that once you get to approx microvolt, you have to take into account things like the temperature difference between plug and socket because the thermoelectric effect kicks in. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] cheap USB voltage sensor
If you have a PC and an AC coupled audio interface then send a low frequency audio saw tooth wave to the audio out. Connect that and the device to be measured to an LM311 comparator. The comparator will flip when your output voltage passes the DUT's voltage. One could get fancy and use multiple comparators Then connect the comparator(s) to a parallel port. You get 8 channels of low bandwidth analog input for about 25 cents per channel, if you already have the parallel port. I think that is the cheapest possible way to get voltages into a computer. Also this kind of ADC can be very accurate. You can tie one or more of the LM311s to a voltage reference and then your instrument is continuoly calibrated. This works because in our case the signal, has low bandwidth so we can take out time and collect 1000 samples On Fri, Jan 13, 2012 at 12:02 PM, beale be...@bealecorner.com wrote: 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/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] cheap USB voltage sensor
Right, Poul! And I've found, by lots of headbanging on walls, GROUNDLOOPS! even at 12 bits... Don Poul-Henning Kamp In message 20120113200200.14805.qm...@s421.sureserver.com, =?iso-8859-1?Q?be ale?= writes: 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 Did you try to hold the battery in your hand while you did that ? :-) Be aware that once you get to approx microvolt, you have to take into account things like the temperature difference between plug and socket because the thermoelectric effect kicks in. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. R. Bacon If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
