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vrf Reading Direct IO data from instrument

Question asked by VRFuser on Apr 27, 2006
Latest reply on Apr 27, 2006 by VRFuser
Jerry,
 
What I did to display the frequency properly was to use the Log Ramp function. There is also a Ramp function for linear frequency distribution. In any case there are 3 paramters for  this function they are min, max, and number of steps (dim size) the output of the function is an array with the correct number of points with the correct starting points and ending points. I entered in the values for min max and read the number of elements from the 3562A. Rather then manually enter in the min and max values it might be better to use the data from the 3562A directly so if you change sweep range settings you woudl dynamically change the (log) ramp function ouput as well.  Hope this helps with your problem.

         Regards
 
         Greg

"Blimbaum, Jerry CIV NSWC PC" <jerry.blimbaum@navy.mil> wrote:

thanks again....your idea worked like a charm......however, still stuck with one more dilemma that I can't figure out.....namely the frequency values.....I read the start frequency and the frequency span from the HP and then with the number of points I form a delta freq on the x axis...in this case it works out to freq span/801.....but the y value from the marker reading doesnt line up with the graph.....if i look at the instrument state and check for bin width it comes out to 187 Hz.....but if I multiply that by 801 points I get a frequency span of about 150 kHz when the frequency span is only 100 kHz.....

any suggestions??


thanks...jerry

________________________________

From: Greg Parrott [mailto:sherekhan_kl@yahoo.com]
Sent: Tue 4/25/2006 8:40 PM
To: VRF
Subject: RE: [vrf] Reading Direct IO data from instrument


According to the programming manual at array position (40) of the data there is a Y scale factor value and the information in the manual also states the data has to be multiplied by this Scale factor to be correct. Also upon reading further that that the method I used to get data form the unit is not as accurate as the display. Since I only wanted a printable plot with my program that was ok for me.

I do not see in my program any issue with Scale factor everything I run comes up with a 1 for the scale factor apparently. At least my user has not complained yet. I will have to make corrections I'm sure.

For the marker information it appears it is read directly what is diplayed on the front panel and there is not scale factor listed for the marker.

I would extract from your data the array position (40) and see if there is a 3 there. If so then that is your fix multiply all your data by the number in that location.

Another option is to use the DDAS command which will dump the display data in ascii format. It is a bit different then DCAS command that I was using but I did notice it does not have the scale factor issue.

You would have to modify some of the coding that I sent you as the data starts at a different location then (116). You would have to look at the information dumped to see where it starts at.

Hope all this helps. By the way I found the programing manual on Agilents web page here is the link.

http://cp.literature.agilent.com/litweb/pdf/03562-90031.pdf

Regards

Greg

"Blimbaum, Jerry CIV NSWC PC" wrote:

If the marker reading were also off then I could buy it....but the marker reading is exactly what's on the screen.....so the fact the two types of reading , ie.. marker and DCAS, give different results is strange....

________________________________

From: Greg Parrott [mailto:sherekhan_kl@yahoo.com]
Sent: Mon 4/24/2006 8:53 PM
To: VRF
Subject: RE: [vrf] Reading Direct IO data from instrument


Just a guess maybe there is range information that has to be applied to the output data. Not too sure all the data I use with mine is in volts 0 to 1 volt for example. I'm not using the DB scale. So I have no idea why the factor of 3 issue.

Not too much help but at least if nothing else use some math on the data.

Regards

Greg



"Blimbaum, Jerry CIV NSWC PC" wrote:


Greg....your code worked like a charm (although, I also had to PAUS the HP before DCAS)....thanks....however, I'm still left with one dilemma......when I plot the waveform (Power Spectrum dB) from the HP the values on the plot are off by a factory of three.....however, the result of the Read Marker is exactly what the HP reports on the screen......so far i dont have the slightest idea for why this difference.....the HP manual says that the DCAS command gives you exactly what's on the screen....

jerry blimbaum

________________________________

From: Greg Parrott [mailto:sherekhan_kl@yahoo.com]
Sent: Wed 4/19/2006 8:14 PM
To: VRF
Subject: Re: [vrf] Reading Direct IO data from instrument


I made a slight error in my vee program for reading data from the 3562A here is the corrected version.



"Blimbaum, Jerry CIV NSWC PC" wrote:

I am trying to acquire data from a 3562A HP signal analyzer.....the manual says it transfers GPIB data in Ascii format.....is this the correct command for retrieving that data?

Read TEXT a Real 64

Also....if a header is retrieved that contains numerics and text info what does one do then?

also....sometimes the Signal Analyzer screen says 'Waiting for HP-IB' and gets hung up.....I send it the ABORT command but still it gets stuck....any other command I should send it?

thanks....jerry blimbaum

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