Setting external trigger with tktds1k2k library for controlling tds 2022 oscilloscope

[Shyam S]

Hi,
 I am trying to use the tktds1k2k library for acquiring data from a Tektronix TDS 2022 oscillscope. Normally, the 'Getting started' VI which allows channel selection(CH1/CH2) automatically sets the trigger source as the selected channel itself. But, I would like to use an external trigger for my application. I noticed that the trigger option is set through the 'Configure Edge Trigger Source' VI. So I tried changing this to a constant value of 'EXT' ; but this wouldnt work. I tried using a different string- 'External'; which did not work too. I received the following error that the trigger source is invalid:

Error -1074135008 occurred at tktds1k2k Configure Edge Trigger Source.vi

Possible reason(s):

Driver Status:  (Hex 0xBFFA0020) Channel or repeated capability name specified is not valid for the instrument.

Secondary Error: (Hex 0xBFFC0002) Parameter 2 out of range, or error occurred while setting Parameter 2.

Elaboration: Trigger Source

Has anyone been able to use an external trigger with a TDS2022 oscilloscope. I had earlier tried Signalexpress with the tktds1k2k library for acquiring the data. In Signalexpress too, there is no option to choose an 'external' trigger. Any suggestions would be helpful.

Thanks,
Shyam

[Dennis_Knutson]

Which driver are you using? Neither the LabVIEW project style or the LabVIEW plug and play driver have a function of that name and neither will allow you to even write a string to the trigger source.

[Shyam S]

I tried using both these drivers and they did not seem to work. Would there be another way to use an external trigger or allow the drivers to accept a string for an external trigger source.

Thanks,
Shyam

[Dennis_Knutson]

If you want to get the LabVIEW drivers to work, you need to explain exactly why they don't work. I figured out that you were using the IVI driver and if you want to get that to work, you just have to wire the correct value to the input. You just can't wire any string that you want. The source input is a combo box and you can right click on it and select Edit Values to see the actual values that need to be passed to it. The easy way to get the correct value is from the block diagram where you call the function, right click on the input and select 'Create Constant'. You will have a comb box constant on the block diagram that you can pick. The actual text that needs to get passed is VAL_EXTERNAL.

[Shyam S]

Thanks for letting me know. I shall try using 'VAL_EXTERNAL' as the string input to the trigger source.

I originally wanted to use Signalexpress tektronix edition to acquire the oscilloscope data since I am more comfortable using the inbuilt functions in Signalexpress for further signal processing. Since I couldnt choose to give an external trigger source using the tktds1k2k IVI source, I tried changing the library files to acquire data directly through LABVIEW. In doing this, I encountered the above error because I couldnt figure out how to set the external trigger source.

 I would still like to use Signalexpress if possible to acquire data with an external trigger. I dont mind keeping the trigger source in the 'Configure Edge trigger source' as a constant value of 'VAL_EXTERNAL' since its the only thing I require currently. Do you know if this would be able to override the choice of the 'trigger source' that I specify for the tktds1k2k IVIsource in Signalexpress.

Thanks,
Shyam

[Dennis_Knutson]

Sorry, no. I've never used NI's Signal Express let alone the Tektronix version. I've always had the full version of LabVIWE and habve been able to everything with that.

[Shyam S]

Thanks for letting me about the 'VAL_EXTERNAL' string. It worked perfectly and I am able to trigger the oscilloscope externally using Labview. I am still trying to figure out if there is a hack to alter the way Signalexpress accesses the trigger sources.

Thanks,
Shyam

[PatrickC]

This should also be possible in SignalExpress. There were two versions of SignalExpress Tektronix Edition released, if you go to your about box and click on Tektronix Edition, does it say version 1.0.0 or 1.1.0? The second added explicit support (a specific step instead of the IVI steps) for the Tek 1k2k instruments. Are you using this Tektronix TDS2000B step, or the IVI Scope Acquire step? With the Tek TDS2000B step, you should be able to set the Trigger Source to Ext and set the trigger mode appropriately (probably Normal instead of Auto roll). The IVI steps in SignalExpress are unfortunately more limited in terms of Trigger Source and cannot use External Triggers.

If you do have the 1.0.0 version of SignalExpress TekEdition, you should be able to download the latest one from our website: https://sine.ni.com/apps/utf8/nigb.main?code=GB_EVALSIGEXPTEK

Let us know if this resolves your problem,

Patrick Christmas

[Shyam S]

Thanks for letting me know. It worked perfectly. Its exactly what I needed.

Thanks,
Shyam