prob in freqency of the acquired signal

[pani]

Hi frnz,

      I have a prob in acquiring a signal. By using DAQ iam generating a sine signal and iam acquring the same. During the runtime

  i need to change the frequency. The Prob here is delay in changing the frequency. If the output sampling rate is 1000 then there

comes a delay in varying the frequency. If the o/p rate is 20k then immediate change in frequency occurs, but the frequency

acquired here is a multiple of 20 depending on the O/P rate.

  Eg:             generated frequency=10Hz

                                   O/P RATE : 1000 ==>acquired frequency  = 10Hz

                                   O/P RATE : 10000 ==>acquired frequency= 100Hz   

                                   O/P RATE : 20000 ==>acquired frequency= 200Hz

                Please help me out with this prob...........

[Anil_Reddy]

u did not attach 2 Sub VIs required.

at what rate u r sending output and acquiring. If you are doing input and output simultaneously using the same DAQ card,  you should follow a relationship between sampling rate for input and output. Most of the DAQ boards use the same time base, so you can not acquire at the rate you want to.

Let me ask you few questions?

what is your output rate?

what is input sampling rate?

Are you using the same DAQ board for simultaneous Input and Output? 

what is the sampling info you are giving to sine wave generator?

[pani]

Hi Anil,,,,

output rate              :    20k

input sampling rate :     90k

yes i am using the same DAQ board(6215) for simultaneous Input and Output.(I am doing the loopback)

sampling info : Fs  = 1k

                       #s =  10k.

There are no sub VI's. You can run the program as it is. 

[Anil_Reddy]

overshoot read DAQ1.vi 

overshoot write DAQ1.vi

these VIs seems missing....

Many DAQ boards needs to maintain a relationship between Input and Output rate when done simultaneously. Output rate should be multile of input rate by 2 power "n"..n is an integer. 

Keep the no.of samples in the "sample info" and output rate same..and try again....

do a simple example VI first, with simple acquisition and generation. 

[pani]

K.Thanks Anil. I got the solution.

[Anil_Reddy]

got the solution...great.........what was the problem?.....wht did u fix?....it would be nice if u can post here...........

[pani · Accepted solution]

hi. Here i attatched my VI.Go through tat.....