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Getting all 3 Peak Power Levels

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 Razi
(@razi)
Active Member
Joined: 12 years ago
Posts: 9
Topic starter  

hi
i am always traying to get the tree peaks powers present in the spectrogram, last discussion i forgot to tell you that i am using Labwindows, so i cant see the spectrogram (PEAKs of course), i am just communicating with the spectran 6065 by using your API docs, so, i wanna describe again my problem:

i am also using a RF generator power=0dBm

i used this commands lines:

STRATFREQ=880
STOPFREQ=920
Rbw=1M
Vbw=1M
reflevel=-10dB

USBMEAS=1

then ....

i try to get :
PEAK1POW 0X80
PEAK2POW 0X81
PEAK3POW 0X82
PEAK1FREQ 0X84
PEAK2FREQ 0X85
PEAK3FREQ 0X86

USBRESET=1

USBMEAS=0

results:

0
0
0
0
0
0
WHAT IS THE SOLUTION???


   
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(@mm_dev)
Reputable Member Admin
Joined: 13 years ago
Posts: 330
 

The PEAK* variables contain the values that are displayed in the relevant fields on the Spectran display. If the field is empty or currently being refreshed you will get 0.0 as result (that, depending on settings, can occur very often). They are therefore not a reliable datasource. You should read the actual measurement values and extract the relevant peaks yourself.


   
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 Razi
(@razi)
Active Member
Joined: 12 years ago
Posts: 9
Topic starter  

OK,

Now, i read data from spectran (after i put USBMEAS=1), so i get many recieved frames and i have some remarks:

first the spectran send 0x31 0x60 then 0x21 (witch means that USBMEAS command was validated), after that 0x0(sucess operation), and then 0x22; the begening of the first measurement frame.

Now, the ID 0x31 0x60 is repeated every 64 bytes!!! witch allow me to get just 3 value points(Freq/Power)!!!, i have saw in an other discussion that the frequenciespoint number = SPAN/RBW *2 , that's mean that i supposed recieved (1M/10K *2=200 points(value) ; so i need 200*64/3 =4267 bytes to read 200 frequencypoint)...... Problem..
1. i cant get the 4267 (even if my buffer has 8192 bytes), and the maximum bytes recieved are 256 bytes<<<<<4267bytes)

2. i i should begin with Freqstart but what i have is an other frequency !!!!!, the next freq is not incremented by the RBW/2 factor; SO AS RESULT I CAN NOT GET THE MAXIMUM POER VALUE;

Please give more informations and clarifications for my problem..

THanks


   
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(@mm_dev)
Reputable Member Admin
Joined: 13 years ago
Posts: 330
 

How do you communicate with the Spectran? The sequence 0x31 0x60 doesn't correspond to any spectran reply, maybe that's just usb protocol stuff or padding data. Second, the parameters posted above don't match the numbers in this post, please clarify. Also as posted in the other thread the formula for number of sample points is just an observation, not a reliable definition. Third you have to receive the data continously, you cannot wait until a sweep is complete before reading it (internal buffers will overflow). Last, frequencies are subject to rounding errors and other processing, so you cannot rely on results being on exactly the same frequencies you set as start- and stop, they can be off by a small delta.


   
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 Razi
(@razi)
Active Member
Joined: 12 years ago
Posts: 9
Topic starter  

Hi,

Ok, i am using VISA USB driver form ''National Instrument'', using LabWindows, so with VISA driver i can open my own ressource manager to communicate with the Spectran, the first command that you have mentioned in the API Doc ; the VERIFY one is verified; Now, my Read_buffer store all data reading from the unit.

when i want to hav measurements i parameter :
STARTFreq, STOPFreq, ....USBRWREST=1, USBMEAS=1. after that i read my Read_buffer (LOOK attachment) , i read just 256 bytes, just one time and to have a new measurement value i need to repeat the hole process (Start,.....USBMEAS=1), as result i cant get peacks values present in my frequency band.

NOTA:
RBW=10K
VBW=10K
START=880M
STOP=920M
SWEEPTIME=1000ms


   
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(@mm_dev)
Reputable Member Admin
Joined: 13 years ago
Posts: 330
 

Sorry, but we cannot provide support for random 3rd party drivers.


   
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 Razi
(@razi)
Active Member
Joined: 12 years ago
Posts: 9
Topic starter  

I am sorry ? but i cant understand you? what do you mean by the random 3rd party drivers.


   
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(@mm_dev)
Reputable Member Admin
Joined: 13 years ago
Posts: 330
 

I mean we have no idea at what level that VISA driver is working, what data it does or does not report, or wether it works correctly at all. We cannot provide support for access levels below the ftd2xx driver api as those protocols are ftdi specific.


   
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