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Measuring Voltage on a Computer

Posted: Sun Dec 01, 2013 4:32 am
by Aidan Cookson
I was wondering if anyone has any tips on measuring continuous voltage and or current through a computer to collect and graph? For the time being, I am planning on going up to 40 Kv at 10mA. I was thinking of using a standard 1:10000 voltage divider then hooking it up to a multimeter(set to 40 DC V max) with an RS232 serial port to USB adapter.

Here is the device I was thinking of purchasing: http://www.multimeterwarehouse.com/MS8226Tf.htm

Would this work or is there a better/cheaper device I could use? I want to measure as many things as I can as this is for a school project, so it will be used for research.

I have also heard that 20mA is the minimum current, but you can get by with less if you have a good enough vacuum. Is this true, or am I confusing two separate factors?

Re: Measuring Voltage on a Computer

Posted: Sun Dec 01, 2013 7:20 am
by Ross Moffett
That can be made to work easily for a single data point, and with a bit more effort, for two.

There are better/cheaper devices for data logging in my opinion, but in order to use those you'd need the kind of knowledge far beyond knowing only what they are. I turn to Arduino for most temporary breadboarding and make a permanent circuit later if it's necessary, when the debugging is finished. There are also devices 10x more expensive that do basically the same thing as that multimeter, but feed into some proprietary system (National Instruments, here's looking at you).

Re: Measuring Voltage on a Computer

Posted: Sun Dec 01, 2013 8:44 am
by Jerry Biehler
A cheap option is a Teensy 3.0. It has a much higher useful analog resolution, 13bits. You just need to scale down lower, no big deal. It is programmable with the arduino software kit too. And only $19.

Re: Measuring Voltage on a Computer

Posted: Sun Dec 01, 2013 3:52 pm
by Aidan Cookson
Ok thanks, I'll look into those. Do you know the maximum voltage I can input into the Teensy 3.0 board? Im trying to figure out what scale it needs to be.

Re: Measuring Voltage on a Computer

Posted: Mon Dec 02, 2013 12:02 am
by Jerry Biehler
crabcookies wrote:Ok thanks, I'll look into those. Do you know the maximum voltage I can input into the Teensy 3.0 board? Im trying to figure out what scale it needs to be.
The teensy is a 3.3v chip, so I think that is the limit. No big deal, just change the values of your voltage divider. Make sure you use high value resistors so you dont load down the little output you have,

Re: Measuring Voltage on a Computer

Posted: Tue Dec 03, 2013 3:47 am
by AllenWallace
I recommend a $29 USB DATAQ device. You get 10 bit resolution from -10 to +10 volts with a Visual Basic interface.
see http://www.dataq.com/products/startkit/di145.html
For the high school students out here, they give them away free...

Re: Measuring Voltage on a Computer

Posted: Thu Dec 05, 2013 12:44 pm
by Aidan Cookson
AllenWallace wrote:I recommend a $29 USB DATAQ device. You get 10 bit resolution from -10 to +10 volts with a Visual Basic interface.
see http://www.dataq.com/products/startkit/di145.html
For the high school students out here, they give them away free...
Thanks, i'll check that out too.