SR830 Lock-in-amplifier Delayed reading data

[theInfiniteOne]

Hello, 

I have the SR830 and its driver installed. I changed one of the examples to give me continuous data, show a plot, and send that data to a text file. However when testing it there's always a delay from 3 to 15 seconds of either no data or junk data. Can someone help me remove this delay?

[cstorey]

Try reading just the data you need, not everything at once.  I imagine there's a time constant setting that affect how long it takes to read one of the inputs and it needs to wait.  In general I can get channel 1 data back in 16ms from the SR830 in my lab, don't know about ch1+ch2...but I could try monday.

Are you connected by GPIB or serial?  Also, search these forums for bug reports about the SR830 driver...it has some quirks.

Craig

[theInfiniteOne]

Hi,

Connected GPIB in parallel with a Keithley 6221 sending AC to it. I need to read both channels at once. I'm not sure how to only read voltage & phase. 

[Ben]

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@theInfiniteOne wrote:

Hi,

Connected GPIB in parallel with a Keithley 6221...

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GPIB is not parallel. If you need to talk to more than one, then use more than one GPIB interface.

I suspect NI IO Trace would illustrate that fact that Dennis taught me many years ago.

Ben

[mcduff]

I do not have the driver installed but the SR830 manual is your best friend. I imagine you are using the SNAP command to get multiple values at once, if you are using the OUTP and OUTR commands your time delay will be greater.

(The manual)

The SNAP? command records the values of either 2, 3, 4, 5 or 6 parameters at a single instant. For example, SNAP? is a way to query values of X and Y (or R and q) which are taken at the same time. This is important when the time constant is very short. Using the OUTP? or OUTR? commands will result in time delays, which may be greater than the time constant, between reading X and Y (or R and q).

What is your time delay in the loop? If I recall correctly the fastest update rate could get with SNAP was 25Hz or 40 ms. From the manual

(Manual)

The frequency is computed only every other period or 40 ms, whichever is longer.

If you try to spin that last  loop as fast as possible you will backlog the command buffer.

mcduff

PS You may want to give this a try prova (There may be some useful VIs there.) I am pretty embarrassed to share it as my LabVIEW code then is not up to par. Just don't ask for any support. It may still work, even though it was written around version 8.