ac voltage measurements with ni 9219

[Hooovahh]

Well did you try increasing the sample rate in the DAQ Assistant?  It is set to 1.95Hz?  Open the DAQ Assistant and change the rate.

[johnsold]

The 9219 in High Resolution mode has a conversion time of 500 ms, so this device is completely unsuitable for AC voltage measurements. Even in High Speed mode the conversion time is 10 ms => rate = 100 Hz. That is not fast enough for effective measurements at power line frequencies as you have been told by several other people.

Get a faster device.

Lynn

[Hooovahh]

Oh I see it now, so under the Device tab the ADC Timing Mode is set to High Resolution, set to High Speed will allow the sample rate to increase to 100Hz.  But yeah still terrible hardware for sampling a waveform.

[scottrod]

For the archives, the command in CVI is:

ret = DAQmxSetChanAttribute (TaskHandle, "", DAQmx_AI_ADCTimingMode, DAQmx_Val_HighSpeed);

OR

ret = DAQmxSetAIADCTimingMode (TaskHandle, "", DAQmx_Val_HighSpeed);

Keeping the second parameter blank "" causes it to apply to all channels.

Also keep in mind this setting goes from 10 mS/S/ch to 20 mS/S/ch if any of the channels are set to thermocouple instead of voltage.

[RavensFan]

Why would we need something "for the archives" about a CVI command posted in the LabVIEW board?

[scottrod]

Because it was the most-compatible hit on the NI lexer, and not even the guys at NI tech support could answer the question for CVI.

I just thought someone might find it useful, but I'd be happy not to spend my time posting helpful tips in the future.

[RavensFan]

Please continue to help and post tips.  But it would be helpful if you posted in the CVI forum.  It provides no help to someone using LabVIEW.

What does "lexer" mean?  I guess you meant to say NI website.  ??

[scottrod]

Google.

[RavensFan]

I did.  It doesn't mean anything related to the way you used it in your message.