Read data driver not giving exact values

[UofH]

I am trying to get the data from an OSA usinf the Labview read data instrument driver. It most of  the time shows the spectrum similar to the OSA in the Labview waveform grapf but the values, meaning the x-axis and y-axis values do not at all correspond. I tried changing the range using min,max and increment but did not work.Please advise. Here is the snapshot of the graph obtained and the little program is also attached.

[Robert.Bedford]

It sounds like your instrument driver does not work as intended.  I can't find the Anritsu MS9710 unit, but I can find  MN9610 and the MS9720, either of which *might* work.

Good luck.

Message Edited by Robert.Bedford on 10-20-2005 11:00 AM

Message Edited by Robert.Bedford on 10-20-2005 11:02 AM

[Emilie S.]

Hi UofH:

Where did you get this driver from?

Emilie S.

[UofH]

Hi
I got it from the manufacturer's website. http://www.us.anritsu.com/downloads/default.aspx
type MS9710 in the search bar. I think I used the ones that came with the instrument, although there is not much difference between the two.

[Dennis_Knutson]

I'm not sure why the Y axis values would be off but there's no reason for the x axis to match the instrument at all. You're getting nothing but a 1D array from the instrument and wiring it to a graph. There is no timing information included in an array. A graph will default to a t0of 0 and a dt 0f 1. You should be able to get this information from the instrument so that you can set t0 and dt to match what the instrument is using. You can set the graph to match with a property node Xscale.RngStart and Xscale.Rang.Increment. You could also create a waveform datatype from the y array and setting t0 and dt. You're not setting any parameters of the instrument in your program. If you did, that would be another way to get the information.

[UofH]

I tried using a property node for the graph. The x-axis increment chnages but the start does not change at all. It only starts from 0 no matter what!! I tried changing the min too.
The waveform shows the scale starting from the min or the start Ispecify but there is no graph at that value!! When I scroll to the 0 of x-axis, I see it.

[Dennis_Knutson]

I'm sorry, you're correct. The correct properties are Xscale.Offset and Xscale.Multiplier.

[misio-pysio]

dont know if the topic is still alive but try using XY graph instead of waveform graph, which is meant to be used with time functions (and you plot against wavelength)

i has similar problem and this greatly helped!

regards

[Dennis_Knutson]

That's not exactly correct. The waveform graph is meant to be used with data that is evenly spaced on the x axis. The XY graph is meant for unevenly spaced data. The x axis on either the wavefrom graph or XY can can be time or it can be any other quantity. Both graph types have the x axis labeled as time but that is just a label, it can be anything.

[misio-pysio]

ok i didnt really know what i was writing about then:)

but still i know from my own experience that the 2 types of graphs behave in different way when user tries to format x-axis

i had a program where 1 frame (have multiple frames in while function to control an instrument) was devoted to reading from the instrument and displaying a graph

i read not only data but also start/stop points on x axis

before i displayed data i used this additional info to format the graph using property nodes and it worked but then i pased data to the graph and x-axis was forced back to display number of points (i also set labels in the same way and it worked perfectly well for labels)

it also resulted in graph flickering

that was when i was using waveform graph, changing it simply to xy graph (and casting data to proper format)  fixed the bug

this hint and the explanation: 'Waveform graphs plot data as a function of time, you can't directly define the data on the X Plot. To do this you need to use an XY graph.' i got from one NI engineer:

http://forums.ni.com/ni/board/message?board.id=170&message.id=231199&jump=true