USB powered 4-20mA source

Hello,

Does anybody have ideas for building a compact 4-20mA / 0-10V calibrator powered through a USB?

I did get some ideas from http://www.plctalk.net/qanda/showthread.php?t=45341 however it would be great to have a compact portable unit working off an USB a.k.a 5V dc

Well, you could look at something like this from LabJack, and add a 0-10V to 4-20ma converter, but it will only be a testing tool, not a calibrator.

Why not just get a standard process calibrator? Traceable, certified, hand-held, simple.

5 VDC won't provide enough voltage to calibrate most devices which use a 250 ohm resister to drop the 4-20 to 1-5 VDC. It certainly won't provide enough voltage for a 0 - 10 VDC calibrator.

Of course you might be able to create some AC from the USB DC, then use a transformer, then convert back to DC...

Sounds like something that might have been fun in my younger days (long before USB) but I'm pretty sure an off the shelf unit would be more cost effective, reliable, professional...

AANZ said:

Hello,

Does anybody have ideas for building a compact 4-20mA / 0-10V calibrator powered through a USB?

I did get some ideas from http://www.plctalk.net/qanda/showthread.php?t=45341 however it would be great to have a compact portable unit working off an USB a.k.a 5V dc

Click to expand...

You need about 15V to power the loop
So boost converter should be used
but how about this:
http://www.plctools.com/index.php?option=com_content&task=view&id=26&Itemid=38

Same device sold here: http://plctrainer.net/ or on ebay