Constant current source from USB-6212 (bus powered)

[CRF450_ Kev]

Does anyone have any quick and dirty tricks to get a reasonable constant current out from this device...say in the range of 4-20mA? Accuracy requirement is low.

[Daniel-H]

Kev,

This device can do voltage/current out using a simple task in MAX.

However, the max current out on this device for a channel is 2mA- meaning the max you can do is 4mA.

I'm not sure you're going to be able to do what you want with this particular card.

[CRF450_ Kev]

2mA would actually be fine if there were a way the card get it to regulate it, but unfortunately I don't think there is. Or at least not easily. It's OK thogh since I have other less elegant solutions. Thanks for the reply.

[Daniel-H]

Kev,

You can go into Measurement and Automation Explorer and set up an analog current out task.

I'm not sure how constant it will be, but it should be ok.

Daniel

[CRF450_ Kev]

When I try to generate an "current" analog out task, MAX tells me no supported devices found though the device is correctly being recognized in MAX under the NI DAQmx devices heading. I can still define regulated voltage outputs as expected but no luck with regulated current outputs.

The no supported devices mesage would lead me to the assumption is that this isn't a supported mode with this model DAQ device. Am I mistaken?

[AnalogKid2DigitalMan]

The 6212 only supports voltage outputs.

You could try converters such as these, just an example of one of many manufacturers.

Some modules are bandwidth limited, so be sure to check the specs if you need to make changes in current quickly.

http://www.dataforth.com/functional.view.aspx?ptypeid=9

-AK2DM

[CRF450_ Kev]

Howdy AnalogKid2DigitMan,

I've seen various modules like you linked. That may be where we end up in the end. I was hoping to find something a little less spendy. I've been shocked to learn how difficult it is to find an off the shelf constant current source module that is suitable electrically and also affordable.

Thanks for posting.

[AnalogKid2DigitalMan]

You could always roll your own:

http://www.allaboutcircuits.com/vol_3/chpt_8/7.html

-AK2DM