external dac

[mgorjis]

Hi everybody, I am new to this area and my question may be funny!

I have NI 6210 which doesn't have analog output. It just have AI, DI, and DO.  Can I use an external third party Digital to analog converter with NI6210? 

If yes, which one you suggest? what is the considerations for using third party DAC (such as loading or .... )

Thanx

[Puchkov]

This device (NI USB-6210) does have Analog Output… check the following data sheet:

http://sine.ni.com/ds/app/doc/p/id/ds-9/lang/en

[Aaron_W.]

Puchkov,

The USB-6210 does not have an Analog Output, that spec sheet you linked is for "Bus Powered M-Series USB devices" and it says "Up to 2 AO channels". If you look at the specifications of the 6210 you will notice it has no Analog outputs.

[mgorjis]

yes. exactly, and I want to knwo that whether I can use an external DAC?

[Aaron_W.]

mgorjis,

I don't think there is anything stopping you from doing so. You will likely need an external supply voltage due to limits on how much power you can pull from the USB-6210, but that depends on which external DAC you use. Keep in mind that the digital IO is software timed meaning you likely won't be able to perform updates faster than 1k. This will limit the rate at which you could update your DAC.

I personally haven't used any external DACs with NI hardware and NI doesn't sell any as accessories. The question becomes how much is your time worth? Is it easier to build / troubleshoot something that may or may not work or is it easier to buy a DAQ device with Analog Output channels.

[GOB82]

Hello,

What are you looking to do with the DAC? I'm using a simple 8-bit R-2R resistor ladder connected to my all DIO USB-6501. I run the output from the R-2R through an op-amp circuit and I use it to drive a motor. Cheap and cheerful.

[mgorjis]

Thank you guys for your answer. Actually I want a closed loop control.  I want to get speed on a DC motor as input to NI-6210, transfer it to the labview and send the input voltage of motor as output. Because this voltage should be applied to a motor, it should be analog. But as I said, 6210 doesn't have analog output.  So I have to send voltage in digital format to DO ports and convert it to analog with a DAC.  Where can I find a circuit necessary for DAC and a cheap model to buy?

Thanks

[Aaron_W.]

mgorjis,

The only recommendation I have is to look at parts vendors like Mouser, Allied Electronics and Digikey. They will likely have something that will meet your needs.

[Now_With_Underscores]

If you're trying to do a closed loop control system, it's probably better to build a system with a dedicated AO function, but there's certainly nothing theoretical that's stopping you from using the DIO... if you're dead set on using an external DAC, I'd recommend a high speed digital IO board as the interfacing layer, but that's only if you need the low latency and BW for your particular application... Keep in mind that if your loop 'plant' responds faster than your nondeterministic PC can keep up, that feedback mechanism could make your system unstable... it all depends on how fast you need to respond.

[mgorjis]

Dear John

Thank you for your complete answer. Actually I don't want a control loop.  I just want to apply a voltage to a servomotor (a step-form signal) and measure the output and then compare input/outputs of the motor.  But since the input signal should be generated in the labview, I need a DAC to genrate Analog Output.  Could you please introduce me a model that I can buy online? what is the other hardware I need to use with DAC?

Thank you