using lockin amplifier with NI daq

[aviaashu]

Hello there,

Is it possible to read out analog data from SR 865A lock in amplifier using a NI daq (6353x-series). I need it for microscopy experiments

[GerdW]

Hi aviaashu,

as that amp supports two analog outputs you could read them using your DAQmx hardware.

But I guess the results could be much better by using one of the possible communication options of that amp. It supports GPIB, RS232, LAN and USB according to SRS website… There are ready-to-use device drivers available!

[aviaashu]

Thanks Gerd w. Actually in my experiment, we are raster scanning the sample for imaging. The sample is placed on a xy stage. Our labview program coordinates between the movement of stage and data collection. For example if my image is a 256 x 256 pixel square image. The stage moves to one particular pixel at one time , registers the data and then moves to other point. Finally the image is stitched. When the lock in was not needed we directly fed the output from our detector which is a voltage output to the NI daq. IF you can clarify a little more that whether what I am trying to do can be done using the RS232 or GPIB for that matter.

Thanks in advance.

[mcduff]

You want to measure R/Theta or X/Y for each point of your scan. The lockin has analog outputs that you can digitize to get values of the parameters on the display channel with your digitizer. However, the analog outputs were meant to drive strip chart recorders and the output is from +/- 10V for a particular gain setting on your lockin. So if you don't change your gain at all, then you can scan like you have been scanning before. If your gain changes from point to point, then you need to scale your readings by keeping track of the gain. For example your gain is set for 1mV, the analog out reading is 5V, then your signal is 500uV.

GerdW suggested "talking" to the lockin directly, that is, rather then digitize the output, query the lockin and ask it what is the value of R or X or whatever. You need to look in the manual for the command. You talk the lockin over a USB, GPIB, or serial line.

mcduff

[Qincaimao]

Hello,

May I ask if you ended up using both lock-in and daq for microscopy? I have a similar task here. I have a daq to read the output both for scanning coordinates and intensity at the same time so that I can plot a SEM image. Now I need to use a lock-in amplifier for the intensity before it goes into the daq. However the lock-in will cause delay for the intensity output because of the time constant. Did you figure out how to deal with the scanning coordinates and delayed signals? Thank you very much.

Best,

Yu