# USB Voltmeter

1. Nov 2, 2009

### swuster

I'm looking for a device I can use to measure analog voltage (up to 25V) and send the data to a PC via USB. Only really need one input, though it wouldn't hurt to have more. My main concern is that it needs to be pretty small and light - any ideas?

The few I've seen online are either too bulky or too costly. It would also be nice to have some sort of software platform to display the data as well..

Thanks for the input!

2. Nov 2, 2009

### vk6kro

Last edited by a moderator: Apr 24, 2017
3. Nov 2, 2009

### MATLABdude

Last edited by a moderator: May 4, 2017
4. Nov 2, 2009

Well, the thing is I'm looking to try and have wireless voltage monitoring. We've already got the wireless infrastructure working in the form of a USB device server which broadcasts to a router; hence I need an option that is as portable as possible. Spending $70 on a DMM for its PC interface ability seems overkill when all I really need is the voltmeter and the PC output. 5. Nov 2, 2009 ### vk6kro I just fed "USB voltmeter" into Google and got dozens of products. So, try that and have a read of what is on offer. 6. Nov 2, 2009 ### MATLABdude If you know how to program a PIC, and some basic PC interfacing, you could do this for ~$2 plus a few resistors maybe a capacitor, and a connector which will cost twice what you spend on the rest:
http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en533924

This sort of thing is great if you need to make lots (emphasis on lots) of individually cheap voltage sensors. If you don't, you're better off buying a (decent) multimeter since they tend to be quite versatile, and invaluable to any electronics hobbyist. I find serial output to be really nice for automated datalogging (i.e. when you want to monitor something that's running overnight).

7. Jul 19, 2010

### mikeusru

I have a similar question:

I'm making an apparatus for my lab's animal behavior experiment where I need the computer to count every time a mouse completes a circuit between two stainless steel objects. Basically, whenever the mouse touches both things at once, I need the computer to add "1" to the number. Would I be able to get a USB multimeter to do this - are they sensitive enough to measure body conduction? I've seen lots of little USB voltmeters, but don't know what to look for sensitivity-wise (I'm in neuroscience, hard to find capable physicists here).
Thanks!

8. Jul 19, 2010

### Staff: Mentor

As long as the multimeter has a MegaOhm scale, it should be able to pick up the contacts. You'll need to do some "debouncing" of the data, probably. What should the data reflect if the mouse stands in place and hops or something -- is that one contact or multiple contacts?

9. Jul 19, 2010

### mikeusru

A single count should be the mouse making contact (and then moving away) from the 2nd metal sheet (it is always in contact with the first). if the mouse bounces three times, that should register as three counts.
How versatile is the software that comes with the multimeters? As a regular computer nerd with very minimal programming experience, should i expect to make the software count for me, or do I need to get a programmer to help out?

10. Jul 19, 2010

### Staff: Mentor

I don't think it will count for you. You will just get numbers from it at some rate (maybe the rate is configurable?). You would need to process the numbers with your program, to bump a counter for each sample pattern that represents a contact and then a disconnect.

11. Jul 19, 2010

### mikeusru

Thanks!

Also, I read that this can be done with capacitance - connect one plate to the ground of a BNC -> A/D converter, and the other plate to the pin. The signal can then be read as a spike when contact is made between the two plates. the thing is - if I don't have a A/D converter, is it possible to get something similar for cheap (not in the \$1000 range)?

12. Jul 20, 2010

### Staff: Mentor

I think that the resistance measurement will be more reliable, but you'll have to test some mice to be sure.