NI 9264 and NI 9234 Module Synchronization on cDAQ

[JulianML]

Hi there. 

I am new and struggling to get this controller working.

I have a cDAQ-9178 chassis with a couple of c-series NI 9234 modules and a NI 9264 module. I want to generate voltage from NI 9264, say a sine wave whose freq can be changed at any time from the panel, and acquire that voltage (+ other things) using the NI 9234 modules. My problem is that I got a significant delay between the voltage generated and the one measured. How can I synchronize the modules so that I can control my plant and mesure input/output signals with minimum delay? Many thanks!

[dsb@NI]

From the 9234 datasheet on ni.com, the input delay is (40 + 5/512)/fs + 2.6 μs

You can synchronize the start of the AO and AI tasks, and ignore the first 40 acquired samples, but you cannot remove that real (minimum) delay from the system. The 9234 should only be used in control applications where a minimum delay of .784 ms is tolerable. Other input modules use different types of converters that introduce shorter delays.

You can use the DSA and DSG soft front panels to generate a sine wave and acquire signals.

http://forums.ni.com/t5/NI-Labs-Toolkits/Dynamic-Signal-Analysis-HW-Soft-Front-Panels/ta-p/3497079

Is controlling the output frequency of the sine wave what you meant by "controller"?

[JulianML]

Hi Doug,

Many thanks for replying and for your assistance. I will have a look at the DSA and DSG soft front panels. 

To explain it a bit more in detail, I meant an application that aims at reducing the vibration of a plate. I am using some piezo patch actuators to do so, so I need to send a variable voltage to them (calculated from a routine - kind of PID) and measure the plate vibrations (mainly acceleration via IEPE transducers - that's why the 9234's + voltage sent). Essentially the output voltage will be a sine-wave that will vary freq&amplitude in time in accordance with the vibration measured.   

So I just want to make sure that I the hardware is working as It should without significant delays (0.784 ms is fine)

Julian

[J-Barticus]

Hi Julian,

After you are finished with the DSA and DSG front panels, I recommend checking out the following tutorial on how to synchronize C Series modules: Synchronizing Analog Input C Series Modules with NI-DAQmx.

Although the document directly references Analog Input, the synchronization strategy is applicable to synchronization between an AI and AO device. For same rate synchronization reference Figure 3, and for multi-/variable rate synchronization reference Figure 6.

Best,

Jacob