Incredibly slow maximum sample rate of cDAQ-9181 measuring current with NI-9207.

[bradziko]

Hi,

I am measuring 4-20mA current and using only one analog input channel of NI-9207 in cDAQ-9181 chassis. I want to measure with a rate o 100 Hz but I am getting an error message:

" Error -200332 occurred at DAQ Assistant

Specified sample rate is higher than the fastest rate supported by the device.

Maximum Value: 19.230769"

Why is Maximum Value so low? Can I really only measure current with a maximum rate of 19 Hz?

[Akos43 · Accepted solution]

Hi Bradziko,

I am Akos from National Instruments Applications Engineering.

In High-Resolution mode the NI 9207 has a Conversion Time of 52 ms, which is equivalent to a maximal 19.23 Hz Sampling Frequency. Please also see the the 5th page of the datasheet:

http://www.ni.com/pdf/manuals/375206b_02.pdf

In High-Speed mode however you can reach the desired 100 Hz Sampling Rate, since the 2 ms Conversion Time in this mode will allow 500 Hz maximal Sampling Rate. The High-Speed mode you can set in the DAQmx Channel Property Node, similarly to the procedure documented in the following article:

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z000000PAaKSAW

I hope I could help you.

Best Regards,

Akos

[bradziko]

Thank you Akos for your valuable answer. I can only add that in order to switch to High-Speed Mode in  Signal Express you need to go to the tab Step Setup -> Configuration -> Device and change ADC Timing Mode.