01-11-2017 02:52 PM
Hello everyone,
I just started using Labview and I have downloaded the Instruments driver for the sr844 lockin amplifier.
I would like to read of the measurements of the channels and save them in a csv format for post processing.
My main issue is that I cannot figure out how to accuire the data in real time.
If i setup the instruments and continusly use the measure function of the sr844 library in a loop, the update rate is higher than the sample rate. As a results I get "points" than the measured ones.
Anyone has any idea about how to do this?
Sorry it might be quite obvius.
Yiangos
Solved! Go to Solution.
01-11-2017 03:13 PM
Hi Yiangos,
when there is a problem with your VI you shoul dattach your VI.
(And like others will say too: don't post images of code, post real code!)
update rate is higher than the sample rate
Any hard numbers on this?
Do you get any error messages?
I just started using Labview
You surely took the free online courses? (From your spelling of LabVIEW I fear you didn't so far… :D)
01-12-2017 11:19 AM
Hello GerdW,
I have done some LabVIEW tutorials from youtube but I will have a look at the free cources as well:)
The issue I think is that I am calling measure too fast and therefor I get back "dummy" data.
Attached is my VI, I used the SR844 drivers which can be found here. http://sine.ni.com/apps/utf8/niid_web_display.download_page?p_id_guid=04731A85006B078FE0440003BA7CCD...
Yiangos
01-12-2017 01:31 PM
Hi Yiangos,
this is what the ReadMeasurement looks like:
So there is a request send to your SR844 and the following answer of the device is read.
When the device answers with a stale value: read the device user manual and ask the SR844 manufacturers support team!
Why do you try to read the values that often? Why not put a small wait in your DAQ loop?
Does your device allow buffered data fetch? (I don't bother to read the manual of YOUR device!)
01-12-2017 01:38 PM
Oh now I see.
I did specify the sample rate of the device to be 512 Hz so I imagine I could use a 1.95ms delay.
Also it does allow for buffered data fetch. I imagine I would have to wait for all the data to be collected and then be transfered.
If I would like to plot this data with a chart with the X axis being time, I could devide the X axis by (sample rate * number of sumples) right?
Yiangos
01-12-2017 01:42 PM
Hi Yiangos,
If I would like to plot this data with a chart with the X axis being time
You could set a multiplier (=sample interval) for the X axis to mimic a "time scale"…
I imagine I would have to wait for all the data to be collected and then be transfered.
I "imagine" you can read all this in the user manual! Did I mention you should read the f***ing manual? 😄
01-12-2017 01:44 PM
Thank you GergW 🙂