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something to stabilaze the signal

Hello
I am measuring a sinus signal from a servo motor. But when I display it on a graph, the signal is jumping left and right. Is there any way so that the signal would stay still. Like on an oscilloscope, the amplitude changes but the signal is not moving left and right.
One more question,
when a acquire a signal with my DAQ card ( from a 3 faze system), I want to split the signal in 3 signals with a split signals, but I can't. Even if a wire a multi signal line in, I only have 1 output connector., and 1 signal

Boris


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You can configure your graph to be like an Oscilloscope.  
I'm not sure I fully understand why the waveform is "jumping left and right". 
 
I'm not sure I understand what you are trying to do with the split signal at the DAQ.  Are you trying to connect the 1 signal to 3 inputs on the DAQ?  Can you provide more details about this?
 
RayR
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First of all, thank you on your reply..
When I measure a sinus signal the signal is shifting along the x scale. It is moving left and right. How do I configure the graph to act as an oscilloscope screen, so the signal would't move?

When I acquire a signal with DAQ assistant, a choose 3 channels ai0,  ai1, ai2. So I receive a combined signal from data connector on the daq assistant. I then use a split signals, to split an output signal to 3 components, but I only get 1 connector from the split signals icon, even if a resize it. So I must be doing something wrong......
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Boris,

To stabilize the appearance of the signal on your display, you must use some kind of triggering, just as an oscilloscope must be triggered for a stable display. Depending on your data acquisition device and drivers, you may be able to do hardware or software triggering.

Lynn
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Hello Boris,

I'm a little uncertain about your first question but i believe it pertains to the manner in which the display updates rather than noise or jitter in the acquisition itself. In order to control the update mode of a waveform display you have to use a waveform chart instead of a waveform graph, I'd recommend you play around with the "update mode" settings that can be found by right-clicking on the waveform chart and try to find a setting that appeals to you. Let me know if you can't find a way to get it to display in the manner you would prefer. If you're really interested in a specific repeating feature of your data, then using a digital (or analog if your hardware is capable of it) trigger, as Lynn recommended, to initiate a finite number of samples would probably be your best bet.

Now, if I understand your second question properly I take it you're trying to split each channel output from a DAQ assistant express VI. If you set the convert from "dynamic data type" VI to format its output as a 2D array of scalars with each row as a channel the output can be split up using "Index Array" VI's. For three channels I would lay down an "Index Array" VI per channel and wire the output from the conversion VI to each. Then create a numerical constant for the "Index (Row)" connector on each "Index Array" VI and set them to 0, 1 and 2, respectively, to separate the three channels into 1D scalar arrays. The "Index Array" VI can be found on the programming functions palette under the array section. Each channel's data can then be displayed and manipulated independently.

Good luck!

Pavak Shah
Applications Engineer
National Instruments
Pavak S
Applications Engineer
National Instruments
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Thank you Lynn and Pavak on your answers.

Is there maybe an example of how should I do this software triggering to stabilize the signal.

Regards
Boris
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Hi Boris,

Since you are using the DAQ Assistant, the easiest way to software trigger your signal will be using the Trigger and Gate Express VI. I’ve attached an example VI below using this. It’s set to trigger on the rising edge with 500 pre and post trigger samples. Another great example of software trigger at a lower level is the DAQmx example, Cont Acq&Graph Voltage – Analog SW Trigger.vi. This example can be found in the NI Example Finder. To get to it in LabVIEW go to Help >> Find Examples… >> Hardware Input and Output >> DAQmx >> Analog Measurements >> Voltage >> Cont Acq&Graph Voltage – Analog SW Trigger.vi.

Let me know if you have any questions and take care.

Thanks,

Nathan
NI Chief Hardware Engineer
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