How Can I Sample at More Than 2 Hz with My NI 9212, 9213, 9214, and 9219?

Updated Jan 31, 2019

Reported In

Hardware

  • NI-9219
  • NI-9212
  • NI-9214
  • NI-9213

Driver

  • NI-DAQmx

Issue Details

  • I am performing a continuous acquisition with my NI 9219. It seems that regardless of the Sample Rate I select, the device will not go past 2 S/s. How should I configure my device to achieve faster rates?
  • I am trying to read the signals with an NI 9219. I specify the sample rate to 50 Hz. However, the actual measurements only changes with approximately 2 Hz. When I export the data, the exact same value is written for 0.5 s of the recording, before jumping to the next value for 0.5s. I am trying to get a continuous measurement with 50 Hz. How can I do so?
  • I am getting some kind of square wave which I don’t understand. 

Solution

The input modules NI 9212, 9213, 9214, and NI 9219 are built with a Delta-Sigma analog-to-digital (ADC) converters. These allow to trade resolution for higher acquisition speed. This setting is called ADC Timing Mode. 
By default, the mentioned modules are set to High Resolution mode, which e.g. equals a conversion time of 500 ms per sample on the NI 9219 (find this information on page 9 in NI 9219 Datasheet). You can change the ADC Timing Mode, to make your module's acquisition rates higher.

Find descriptions on how to do so in NI MAX/DAQ Assistant, LabVIEW, and LabVIEW NXG in the following.


NI MAX or DAQ Assistant
If you are using NI MAX or a DAQ Assistant to configure your Virtual Channel or Task, navigate to the Configuration tab, then the Device tab, and change the ADC Timing Mode to your preferred setting, e.g. High Speed. On the NI 9219, High Speed allows for a minimum conversion time of 10 ms (100 S/s).


 
 
LabVIEW
In case you are configuring the task programmatically in LabVIEW, you can use a DAQmx Channel Property Node to change the ADCTimingMode property to e.g. High Speed.
 
The ADCTimingMode property is located in Analog Input » General Properties » Digitizer/ADC » Timing Mode.


 
LabVIEW NXG
As the ADCTimingMode property bases on DAQmx, changing it in LabVIEW NXG is done the same way as it is in LabVIEW:


The ADCTimingMode property is located in Analog Input » General Properties » Digitizer/ADC » Timing Mode.

Additional Information

The maximum achievable conversion rates of NI 9212 for each Timing Mode are tabulated on page 6 of NI 9212 and TB-9212 Datasheet.
The maximum achievable conversion rates of NI 9213 for each Timing Mode are given on page 6 of NI 9213 Datasheet.
The maximum achievable conversion rates of NI 9214 for each Timing Mode are documented on page 6 of NI 9214 and TB-9214 Datasheet.
The maximum achievable conversion rates of NI 9219 for each Timing Mode are described on page 9 of NI 9219 Datasheet.

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