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[Getwonder]

Thanks Drew for joining the conversation. 

For the time i implement these things and send you the results pls guide me in detail how to introduce the sampling rate into the already acquired signal.

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Q-As far athe the read/write delay of 0.5 ms, johnsold answered that in their previous post:

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@johnsold wrote:

The 0.5 ms is the approximate time of one byte at 19200 baud.

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So to send one byte requires only 0.5ms.

Thanks very much

[Drew_T]

Intelligent,

To resample data to a new time scale, use the Build Waveform block.  See Code Snippet below.

Data is the data you wish to resample.

Time step is the time between samples

Start time is the timestamp you want data to start at (generally 0)

Also, the 0.5 ms is the time required to send one byte only at 19200 baud.  At different rates, the byte will send at different speeds.

Drew

[Getwonder]

Hello,

I have applied the producer  consumer design pattern and included sampling in data acquisition. I am sharing my result so that you may guide me how to solve it.

Thanks

[johnsold]

What are you trying to solve?  Two images of the front panel does not tell us what you expect the results to be or what is wrong,if anything, with what you show.

The time and amplitude scales on the two graphs are different.  Are these the same signal or two different signals?

Please state specifically what the problem is.  In particular tell us what is wrong with what you have and what the correct result should look like.  After running the program to get the data displayed in the images go to Edit >> Make Current Values Default.  Then save the VI (with a different name if you do not want the data saved in your working program).  Post the VI with the saved data.  It is much easier for us to work with a VI than partial images.

Your data appears to be aliased.  That would indicate that the sampling rate is too low.

Lynn

[Getwonder]

Thanks for joining again. The problem at the moment is that i am not getting the exactly sinewave as i was getting previoulsy.

So what i am missing kindly guide me.

Thanks again.

[johnsold]

I am not sure what is going on.

1. It looks as though you are attempting to sample at rates much faster than you can transfer the data.  The Waveform Graph shows a 10 ns sampling time but your serial data requires sending one character and receiving two at 19200 baud.  The serial transmission time for 3 bytes at 19200 baud, 8 bits, 1 stop bit (10 bits per byte) is 1.56 ms, neglecting any time for the remote device to decode the command and prepare to send the data.  This means the maximum effective sampling rate is 640 Hz.  Any signal frequency greater than 320 Hz will be aliased.

2. It also looks like the signal may be duplicated with some delay, about 12 microseconds.  This may also be due to the aliasing.

What is your signal frequency?  How fast does the A/D converter sample? Does it sample when it receives the "W" command or does that just transfer a previously converted sample to the computer? How many samples does the buffer at the A/D converter hold?  What happens when that buffer is full?

Lynn

[Getwonder]

Thanks again

The Data i have send to you is of 3Hz while i am interested to analyze the signal in range of 0-150Hz.

The board contains max187 which is a 12 bit ADC having sampling rate of 75KHz.

It transfers only the analog signal equivalent data to the PC.

There is no buffer at the ADC side, but the controller just reads the data and transfers it to the PC.

T.C

[Getwonder]

for reference

http://datasheets.maxim-ic.com/en/ds/MAX187-MAX189.pdf

[johnsold]

How is the external board configured?  Does it perform one conversion every time it receives a "W" command or does it convert continuously at 75 kHz?

As long as any other delays are small, you should be OK up to 150 Hz, although you will probably have some timing jitter due to OS latencies.

Lynn

[Getwonder]

Hi,

When the controller receives W it starts getting bits from the ADC and then it sends it to the PC.

I think we are now going close to a sloution this will be all because of your continuous guidence.

Thanks very much.