Read output level from Agilent 33120A function generator

[hhaamm]

Hello,

I'm writing a code to control a tunable laser. I need to get a real-time output level from an Agileng 33120A function generator, which is to control the wavelength output of the tunable laser. I'm wondering if it is possible to get the output voltage level thru GPIB at all (it's not obvious in the manual that this is actually doable). Otherwise, I have to use a DAQ card to real time monitor the voltage level. Because the voltage is swept continously, my concern is that this may cause some sync problem: at a given point of time, the voltage that goes to the tunable laser may not be exactly the one I obtain thru the DAQ card. Could anybody with related experiences  comment on this please? Thank you!

[Albert.Geven]

The best you can do is to generate a waveform with a daq card and with synchronous IO also read data with the daq card. Here you know exactly the synchronisation.

Reading the values with gpib will never be possible at high speed.

Another possibility is to use an oscilloscope they have hig speed possibilities but they have not much resolution. mostly 8 bit, some 12 bit.

[hhaamm]

Albert,

Thanks a lot for your suggestion. Could you recommend some DAQ card that has analog output /input channels? I haven't used any DAQ like that before. Thanks!

[Sarah_Y]

Hi hhaamm,

What speed/frequency are you using in your application?  We offer a wide variety of DAQ cards that can provide this functionality but it's difficult to make a good recommendation without knowing your frequency.  For example, the NI PCIe-6363 has a maximum update rate of 2.86 MS/s and can read in an input at 2 MS/s.  If you need something faster, there is also a line of scope cards that function at higher speeds.  If you can post that information, it'll be much easier to come up with the best card for you.

[hhaamm]

Sarah,

Thank you very much for the recommendation! My application is not very high speed and 2 Ms/sec should be more than enough already. I was using a stand alone function generator before to generator the waveform, which is to control the wavelength of my laser , and collect and intensity value from my photo-diode and voltage value from the function generator using a DAQ card. It works but I always have the concern of the sync problem I mentioned above. Just because the two sets of values are from systems based on their own timing info. I think I'll give the DAQ function generation a shot, as long as the waveform generated this way is of decent quality: smoothness, time jitter...

[Albert.Geven]

The x-seies cards are high performance, you also can choose for usb but the timing restrictions are a bit harder then.

You can sweep on one channel and acquire both output and laser.

Or you can use synchronous IO.

I would start with the input examples of daqmx, it still is an idiot set of examples because the example directories are claiming all kinds of measurement from accelleration through position to voltages (and voltages is the only thing they can measure in fact).

Inside voltages all examples are displayed alphabetically instead of a new set of directories.

What you need to start with is

C:\Program Files (x86)\National Instruments\LabVIEW 2010\examples\DAQmx\Analog In\Measure Voltage.llb\Acq&Graph Voltage-Int Clk.vi

this will show how to get one signal and even more when you fill in something like Dev1/ai0,Dev1/ai1.

synchronous IO is for later.