peak detector

[Ramiyer]

I have an application which used Peak detector.vi . The problem is when I use continously acquired signals directly from the DAQ board the peak detector doesnt give me any output. But If I store the data into a Labview measurement file and then read the labview measurement file and run it through the peak detector I get all the outputs from the peak detector. My question is does peak detector work when I have continous data aquisition and If so How can I do it.  Also I have have 4 channels of the DAQ board from where I recieve the data.

Any help in this would be greatly appreciated.

Thanks

Ram

[gwd]

Maybe you'd better post a vi.

Have you used a probe to look at the input array to the peak detector? It seems to me that if there is ANY data going in it's going to produce some sort of output.

I should also note that there is a point-by-point version of the peak detector (in 7.1).

[Ramiyer]

Thanks for your reply.

I have checked using the probe and there is data going into the input but there is nothing coming out of the peak detector. I am attaching the vi's .

Thanks,

Ram

[gwd]

OK, got it. Your DAQmx Read is set to 1 sample, N waveforms. So the "array" going into the peak detector has only one element. One element, no peak.

If you change to N samples, N waveforms AND attach a constant to the DAQmx Read asking for a specific number of data points it will work.

(The default number of data points is -1, and this means "read all samples currently in the buffer".)

[Ramiyer]

Thanks a lot for your help. It worked!!!!!!!!!

[suffyzull]

hello,
how to change the setting?
i have also try it and i dont have any idea where to explore it?

thanks:
zull azym

[suffyzull]

hello,
how to change the setting?
i have also try it and i dont have any idea where to explore it?

thanks:
zull azym

[Neal M]

Hello zull,

The setting you are looking for is the polymorphic instance (the dropdown box) of the DAQmx Read vi.  I would reccommend looking at the example program (located in the Example Finder in the help menu) titled Cont Acq&Graph Voltage-Int Clk.vi.  It is under Hardware Input and Output>>DAQmx>>Analog Measurements>>Voltage.  This example shows the DAQmx flow that will output the correct values.

If you have more problems, if you could possibly post screen shots of your vi and some more information about what you are trying to do and what you are seeing, that would help greatly.

[suffyzull]

this is my program for the load detector,
and this is where it hard to fine why the signal that measured cannot be detect using
the peak detector, help me please.
i dont know where to setting it.
thanks

[RavensFan]

It looks like you have the DAQ read set for N samples N channels of 1D waveform okay.  What does your signal look like?  What are the amplitudes?  You have a threshold set for 40.  But it looks like your waveform would be -10 to +10.  If so, it would never cross the threshold.

If this isn't the answer, I would recommend running the VI at least once to get some sample data on the indicators.  Do Edit/ Make selected values default, then save the VI and post it.

(By the way, LVDT is linear variable differential transformer, no "s" in "variables" on your main tab.  Variable is an adjective in this case, not a noun.):smileywink:

Message Edited by Ravens Fan on 01-30-2008 11:10 PM