Power vs Wavelength graph for ILX 6810B Optical Multimeter

[Sartaj]

I have been able to interface my ILX OMM-6810B Optical Multimeter to my computer using GPIB 488.2.My experiment requirements include creating a Power vs Wavelength Graph taking data from the Multimeter using Labview 6.1.Can you please help me with the problem?I am quite new to the software so I am not able to get the correct working VI for Power vs Wavelength graph.Please help.

[Dennis_Knutson]

What exactly have you written? Attach the code.

[Sartaj]

I was trying to use the while loop but wasn't able to get the right logic.Actually what we need is that (1) we must be able to write and change the wavelength at our will and (2) the power value from the instrument must be read for every wavelength.Can you please suggest a good logic for carrying out this function? 

[Dennis_Knutson]

A simple while loop is correct but since you did not attach it like I asked, I have no idea what your problem is.

[Sartaj]

Attached are the screenshots of the VI I am using. In 'To be read' we give the command 'POWER?'

It is able to change the wavelength but it is not reading the power value.In 'GPIB Command to send' we write 'WAVE 720' (720 is the wavelength value we need).

[Sartaj]

We didnt use the while loop finally.Through this VI we attempt to write some arbitrary Wavelength value (say 720 nm) onto the instrument and then read the power value.So after enough values we would plot power vs wavelength graph.

[Dennis_Knutson]

One major problem I see is that you have no dataflow between the read and write in frame 2. The read can actually occur before the write does. The simplest way to achieve correct order is to connect the error out of the write to the error in of the read.

I would strongly suggest you use VISA functions instead of the lower level GPIB and I would also strongly suggest you stop using the stacked sequence structure.

[Sartaj]

Thank you very much for your help.It worked.We used the While Loop effectively to create a situation wherein we can decide a)The initial wavelength and b)The step size in which the wavelength should change.But the only problem we are facing now is that the graph is not getting generated.I mean the power values(y-axis) and the wavelength(x-axis) are changing as expected but there is no display in the graph.The graph is empty.Only the ranges of y and x axes

keep changing(as it is in autoscale mode).Could you please suggest a possible reason for this?

Attached is the screenshot of the final VI we are using.

Thank you once again.

[Sartaj]

the frame 2

[Dennis_Knutson]

They way you are writing is incorrect. You are only writing a single point. You need to stop converting the data to an array like that. Create two shift registers - one for an x array and one for a y array. In each shift register, use a build array function to append new data to what is in the shifter register.

p.s. An express XY graph does this for you.