Time Division Multiplexing With DAQmx

[Bennabis]

I am trying to produce a time division multiplexed wave to send 5 separate signals down a single analog line on the DAQ card. The wave appears fine on the Waveform Graph, but when I view the output wave on an oscilloscope, the timing is inconsistent. I am fairly new to Labview, so It is probably something quite minor. Thanks in advance, Ben

[Bueller]

Hi Bennabis,

Can you please clarify what you mean by the "timing is inconsistent"?

On another note, the way the data is plotted on the waveform graph in LabVIEW is based on three things.

1) An array of the amplitudes of the acquires points which constitute the y-axis.

2) t0 : the time when the acquisition started, and it is taken from the system clock.

3) dt : it represents the difference in time between each acquired data point and it depends on the sampling frequency.

Regards,

Faris A

[Bennabis]

The time interval between components of the multiplexed wave is set at 5ms using the wait until ms multiple vi. On the Waveform graph, this 5ms is represented accurately. On the scope (DAQ AO pin) however, the 5ms interval varies from 1 - 20ms in a random fashion.

[Bueller]

Hi Bennabis,

I checked your VI, and I think you are not setting the daqmx task in the best way.

I recommend taking a look at the following two examples LabVIEW Help. The  first one is " Cont Gen Voltage Wfm-Int Clk-Dig Start.vi" where you can check how the task is setup and terminated. In your case you are not using any triggering.

The second one is " Gen Multi Volt Updates-Text File Source.vi " . This example describes how you can read data from a text file and write them to the daq output. It might be a better idea to save your waveform to a file instead of using a shared variable.

Regards,

Faris A

[gerita]

can anybody help me? I have no idea how to do TDM in labview 8.5. Thanks!!!

[Bueller]

Hi Gerita,

Can you please explain more on what you are trying to do. Is your application a software only application or are you trying to generate a signal on a device?

If you are using DAQmx it would be a good start to check the previous posts on this thread.

Best Regards,

Faris A