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Interval Trigger

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Interval Trigger

Postby roastmeat » Tue Aug 13, 2013 5:16 pm

Hi,

I am trying to collect data on the PS 2205 after sending a burst of short pulses (my own hardware). I will be triggering off the transmitted signal (ChB) and collecting data on the received signal (ChA).
I need some guidance in the Labview aspect.

I found out via the Picoscope software that using the 'interval' trigger is my best bet.

The signal I am transmitting is a burst of high frequency waves (1-4Mhz, 10Vpk) at a frequency of around 625 Hz.
Something like this: ||||____||||____

The Interval Trigger values that seem to work are as follows:
Source: B
Starting Edge: Rising
Condition: Greater than
Threshold: 3V
Hysterisis: 2.75%
Time 1uS

1) Is this the correct trigger to use, if so, are the values sensible?
2) What functions do I use to set this up? I know there are 4 Advanced Triggers but do I call all of them and in what sequence?

Thank You.
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Re: Interval Trigger

Postby Hitesh » Wed Aug 14, 2013 2:50 pm

Hi,

If you are looking to trigger when one period of the waveform is greater than a particular time, then that should be fine.

Try combining a Level Trigger and Pulse Width Qualifier for the Interval trigger.

You will need to use the following functions in the suggested order:

  • ps2000SetAdvTriggerChannelConditions
  • ps2000SetAdvTriggerChannelProperties
  • ps2000SetAdvTriggerChannelDirections
  • ps2000SetPulseWidthQualifier

I hope this helps.
Hitesh

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Re: Interval Trigger

Postby roastmeat » Wed Aug 14, 2013 6:09 pm

Thanks Hitesh,

I just found out that I require more data than the scope can handle in block mode, I will have to switch to streaming mode.

Do these functions still work in streaming mode?
If not, is there another way I can work around this?


EDIT:
After looking a bit closely at the functions provided in the dll, ps2000SetAdvTriggerChannelConditions, ...Directions, ... Properties and ps2000_set_trigger all have the same input parameters whereas in the programmers manual they are all different.


Thanks.
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Re: Interval Trigger

Postby Hitesh » Thu Aug 15, 2013 3:16 pm

Hi,

The trigger functions will also work with streaming mode capture.

For the advanced trigger functions, you will need to add a 'Call Library Function Node' for each function call and then configure the function according to the Progammer's Guide. Ensure that the calling convention is set to 'stdcall (WINAPI)'

I'll put some further information that might of use as an announcement on the Forum.

Thanks,
Hitesh

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Re: Interval Trigger

Postby roastmeat » Thu Aug 15, 2013 6:52 pm

I am playing around with the streaming example and one thing I noticed is that the advanced trigger functions as stated in the PS2000.dll (called via Call Library Function Node) have input parameters not corresponding to the Programmers Manual.

For example: ps2000SetPulseWidthQualifier() in Labview has:
-handle
-source
-threshold
-direction
-delay
-auto_trigger_ms

and in the manual:
-handle
-*conditions
-nconditions
-direction
-lower
-upper

I am assuming I have to use a Wrapper dll of some sort but the ps2000wrap.dll does not contain any trigger setup functions.

Another Issue:
I want to measure 1-4MHz via streaming mode.
Therefore I need a sampling interval of less than 1nS,
In the ps2000_run_streaming_ns I set the time_units to 2 instead of 3.
Then setting on the front panel the Sample Interval to 100.

When I run the program it gets hung on the FastStreamingReady Call Lib Funct. Node, always 'saying' the scope is not ready.
I am thinking 1nS is too small and the driver hangs?
Or do I have to change something else.

EDIT:
I need to collect up to 4MHz of signal for about 10mS without skipping any data.
Is this possible?
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Re: Interval Trigger

Postby Hitesh » Mon Aug 19, 2013 2:58 pm

Hi roastmeat,

Looking at your requirement of a <1ns sampling interval, this is not going to be possible in streaming mode with any of our devices due to the limits of the USB 2.0 and USB 3.0 specification.

In block mode, the maximum sampling rate for a single channel is 200MS/s so with 2 channels, the maximum would be 100MS/s and you would be limited by the 16 kilosample buffer.

You may need to consider one of our deep memory oscilloscopes and capture data using Rapid Block mode to capture just the portions of data that you are interested in.

If you could please advise of the number of waveforms that you need to capture, and the ideal number of samples that you require in 10ms, then I can suggest some suitable products.

Thanks,
Hitesh

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Re: Interval Trigger

Postby roastmeat » Mon Aug 19, 2013 3:34 pm

Hi Hitesh,

Thanks for the response.
A sample rate of above 25MS/s should be appropriate to accurately capture the signal peaks.
I have calculated that the smallest time I need to collect data is about 1.6ms after the burst, but I would prefer anywhere around 5-10ms.
Only one burst is necessary.

Thank You.
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Re: Interval Trigger

Postby Hitesh » Tue Aug 20, 2013 2:21 pm

Hi,

I think a block mode capture will be sufficient in this case with a PicoScope 3204A or B:

http://www.picotech.com/picoscope3000.html

This will have sufficient memory as over 10ms at 25MS/s you would have 250,000 samples per channel.

The PicoScope 3204B has twice the memory compared to the PicoScope 3204A as well as an Arbitrary Waveform Generator.

I hope this helps.
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