real time data acquirring

[hanskoh86]

Hi this is Hans here,

in my project, i tried to acquire voltage and current real time reading from a cirucit. When i tried to write the program to acquire these reading at the same time with different channel, it dosen't work. the error msg as per attach.

Can somebody teach me how to acquire these reading at the same time? Besides that, may i know when we need to use trigger function in the acquiring system?(I am using the 8.5.1 version labview and Ni USB-6009 DAQ device. Project tittle is monitoring power system). Thank you for your assist.

thank you and best regards,

Hans   

[KateB]

Since every channel shares the same analog input engine on the same device, you cannot separate the task.

You must create first channel and wire task output to the next create channel to put both channels in the same task, and then, read from multiple channels in the loop.

[hanskoh86]

Hi KateB,

Thank you for your reply. But i still dont understand what your mean. Is it as the program i write in this attachment? But i want to show the current and voltage reading seperately in the different waveform graph. Or can you write and show yours to me as an example? 

Thank you.

[KateB]

You can use Index Array function to separate waveform from each channel.

[hanskoh86]

Hi Kate,

I do as ur suggesstion. But the result come out not as i want.What i want is as below:

1.) i need to seperately get the current data

2.) seprately get the voltage data ( because i need  these two reading to get the power reading) 

3.) show the voltage reading and current reading simultaneously on the different waveform garph.

4.) reading the current and voltage reading simultaneously by using the same device.

[KateB]

Can you attach your code for further analysis?

[hanskoh86]

Hi Kate.B

Could u answer me a simple question. 

what mean by the floating point sample? Is it we connect to the floating signal source so it call the floating point sample?

 how we going to setting in the DAQmx Read.VI? Because now i want to read from an AC signal source by using multichannel method to obtain the current and voltage of the circuit to my pc.

the program is attach as below.

[hanskoh86]

Hi,

In the attachment here, is the signal i acquire from the program i wrote on the attachment reply above. 

I really don't how to setting to get a perfectly AC signal.

Could anyone help me?

 

[KateB]

Sorry, but I never mention about floating point sample.

Where did you hear this word?

For VI, why don't you follow my advise to use Index Array as shown in attached screenshot?

Another thing is that you measure a power line signal with 120Hz which is just 2.4 times of its frequency, and you expect a perfect waveform?

You should at least sampling them at 1kHz.

The best would be 24kHz for two channel sampling by 6009.

Sample to read should be 25-50% of sampling rate.

[hanskoh86]

Hi Kate B,

Thank you, Kate. U help me a lot in this project. Now i'm able to acquire the voltage and current already.

But i have another problem need of assist by you. Hope you can give me some comments. 

1.) This is the case. When case structure active, the waveform of current do not monitor out, but it only able save the waveform to the indicated file. What can i do while on save the current waveform to the folder but also monitor out the current waveform. The Vi will be attach at here.

THank you