Stanford SR 850 Lock in Amplifier

[jikram]

I need to grab real time data from my SR 850 LIA and write to a file. I downloaded the driver from the ni website. 

 http://sine.ni.com/apps/utf8/niid_web_display.model_page?p_model_id=2172

The driver runs one complete scan sweeping across the screen. I want it to continuously grab data at regular intervals. I have a motorized actuator that moves in steps of 2.5 microns so im trying to have it get data at each step. I was hoping someone would be kind enough to point me in the right direction.

Thank you

[Michael_Munroe]

Sounds like the only thing missing is a for loop.  It is typical to move the actuator to the proper position and the perform the complete scan.  This way each scan is at a known position.  Also the loop run as fast as the two operations can be performed.

[jikram]

I assume you are referring to the "getting started" VI. This VI scans the X axis. Im not sure where to place the for loop or when to have it stop.

[Jörn]

You need a loop which does the following:

 - move the actuator one step

 - read the data from the LIA

Repeat until all steps are done.

Just another  hint: I am not familiar with your LIA in detail, but normally reading the x-channel with a LIA means that you register the signal portion which is in phase with the reference. So for getting all information off your signal you need to register also the y-channel which is the signal portion which is 90 degrees off phase from the reference. (Or you switch the LIA to r-theta-mode where r is the amplitude and theata is the phase between signal and reference).

Regards

[Jörn]

read the data: means read one data value from the x and y-channel. There will be a VI which does this job.

Be aware that you need some settling time for the LIA. maybe you need to insert a wait in the loop

[jikram]

Thanks for the posts but what I really want to focus on is getting real time data from the LIA. the synchronization with the motor should be managable. I am modifying the "getting started VI" with little success. The SR850 library function has a read/trace block. If someone can help me use these tools to design a program to do what I want, it would be much appreciated. Please let me know if I need to explain anything 

thanks

[jikram]

To be even more specific, The "readtrace" VI on the "data" tab of the sr850 user library requires the use of the following as input and output connections:

trace(trace1:0)

start bin #

trace data

total points 

i think there should be a way to construct our VI with these paramers and have it perform the required task. Im not sure what kind of connections to make with the above ? suggestions ?

[David_L]

This driver is very specific for this device and chances of someone on here using it are pretty slim, so in the future you might try asking a more broad question. 

This Getting started VI wires in 0 to both start bin and trace, and the totalpoints is calculated based on the sample rate and scan length.  However this totaly depends on how your device works, and how your scans are running.  Like suggested earlier, if you are unsure of how to design your VI with this driver, try working with the getting started and reworking it to suit your needs.

[Jörn]

I would suggest the following: First get a basis understanding of how the LIA is remote controlled (if you haven't got it already) by taking the manual and find the GPIB or RS-232 commands which are necessary to get the desired measurements. Now you make a simple program from scratch controlling the LIA by using VISA-session.

Secondly have a look at the library VI for remote controlling the LIA. There you will find VIs which send the respective commands.

Also there will be some example programs which you could have a look at and maybe you can simply modify them for your purposes.

[jikram]

This was most helpful Jorn. In the manual the programs are written in C and QBasic.. The Labview version would be most helpful. Can you send me the links to the  VIs that communicate remotely ?

Thanks