Jeremy Li

Hello Teles,

Thanks for the feedback. it seem the calculation result is the same between us.

N may have a bit impact on the calculation. but it seems not the key factor of the deviation.
and thanks for the command MEASUrement:MEASx:CPWIDTh.

Thanks for the help always.

And for how can we set the measurement to read channel power programatically.

MEASUrement:MEAS1:TYPe (I mean what string to input here ), or is that means do not support spectrum measurements in this group?P2-874
 

Hello Iris,
Thanks. understood the N and Pk could be found out according to the spectrum data. 

It seems I was able to get the value very close to the value show on the scope screen. but always a bit deviation, no matter I update the CBW or not.

here is another question. I'm not sure how to calculate the N exactly in the scope. because the data point interval frequency(here df=52.6316Hz) from the spectrum data alway to be a floating value instead of the integer. I need to calculate N by CBW/df, it could be a floating value. should I do it round to the nearest integer or what..  it seems when the calculate result is x.5, the deviation is the maximum.

probe compensation source, center frequency 9k Hz, SPAN 40K Hz, RBW:100 Hz.  CBW:1000 or others
Start_Frequency  0
Stop_Frequency   29000
increment  52.63158971
samples    552
 

here is another picture for what I have found.

don't know why the post easily to be messed up by the symbol， but sometimes it is ok.

Hello Alan,

Thanks for the help.

 I have another question about the channel power since I could not recall the value.

Could you help to advise how can we calculate the channel power when we get the waveform of the spectrum view.
（edit: after study,It seems we could not calculate the channel power only according to the spectrum view? am I correct?）

 I don't know how to update the attachment. so I will put what I have found in the next reply.

And how can we set the measurement to read channel power programatically.
I didn't find out the type in the argument list (P2-874). I can set the measurement to TOP, peak to peak,Base

Hello All,
I didn't find out the correct command to read out the measurement result. do you have any suggestion? thanks.
The measurements are channel power, ACPR, OBW.

Hi Teles,
It works, thank you very much.

Hi Teles,
Thanks, just understood that the command MATH:MATH2:VUNIT? is to read the unit of what user defined.
I intend to fetch the unit for the Y-axis label name. 
for example , the unit for MATH2=INTG(CH1*CH2) display on the scope screen is uj or mj, how can I retrieve this kind of string?

Hi All, Or It seems I should  say, Hi Teles, ：-）

I'm tring to retrieve the Units  Manual P2-367 for the Math results,for example:MATH:MATH2:VUNIT?

But I always get "" instead of the correct units.

Could you help to advise what is wrong with my program or what is wrong with the scope setting?

Hi Teles,
Thanks for you patience, according to your instruction, I have find out the answer in LabVIEW help document.

magnitude is the magnitude of the averaged FFT spectrum. If the input signal is in volts (V), magnitude has units of volts-rms (Vrms). If the input signal is not in volts, magnitude has units of the input signal unit-rms. If dB On is TRUE and the input signal is in volts, magnitude has units of dBV

So what I got was dBV ,and 14.01dBm seems close to the scope.