Trouble Shooting Picoscope 5244A Rapid trigger

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Trouble Shooting Picoscope 5244A Rapid trigger

Post by rphicks »

Our goal is to use rapid block mode to collect a sequence of periodic signals on channels A & B that occur at a frequency of 10 Hz. A 1 ms TTL trigger pulse (going from 0 V to +4 V) derived from a signal delay generator (SRS 535) is split by a BNC tee and connected to “Ext.” and “B” to visualize the trigger. For testing purposes, a signal TTL pulse of 10 us width and delayed by 10 us from the trigger is generated by the same SDG.
We initially tested the “” as shown below. We used a resolution of 14 bits, 1,000 pre-triggers, and 20,000 post-triggers (160 us for a timebase of 3). A trigger threshold of 16384 (16-bit count) was chosen. Therefore, upon executing the program, we expected to see the trigger transition from zero to 4 V on channel “B” and the 10 us “signal” pulse on channel “A”. As shown in the screen shot, we observe (1) a high-to-low transition shortly after the start of the time record (around 300 samples) (2) a substantial jitter in the time point where this transition occurs (on the order of 1000 samples). (3) the 10 us pulse on channel “A” is not observed. The signal always stays at zero. All observations are insensitive to the trigger threshold or the chosen voltage range (5 V was used for both channels).
Interestingly, when switching the trigger direction from “Rising” to “Falling”, the jitter goes away and the high-to-low trigger transition consistently occurs at 1000 samples, as expected. Upon shifting the signal pulse by 1 ms (the pulse width of the trigger pulse) on the SDG, the pulse is properly recorded on channel “A”, i.e. it occurs 10 us after the falling edge of the trigger pulse.
If we use the RapidBlock example, we see the same situation. In short, the data suggests that the scope is not properly triggered by when configured to detect a rising edge.
When displaying trigger and signal on the Picoscope 6 software, both signals are properly displayed when triggering on either edge.
Taken together, our observations suggest that it is not the pulse quality or the Picoscope hardware that causes the issue, but rather a Labview issue.

Labview: 2015 (32-bit)
Operating System: Windows 7 Professional (64-bit)
PicoScope® 6 - PC Oscilloscope software version:
Scope: 5244A
Firmware Version:
Hardware Version: 1
Driver Version: (shown on the PicoScope Software) (when using the PicoScope5000aUnitInfo VI)
Firmware Version: /

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Re: Trouble Shooting Picoscope 5244A Rapid trigger

Post by Hitesh »

Hi rphicks,

We have received your e-mail support query about this issue.

What might help is to see your PicoScope 6 settings - could you please e-mail a psdata or pssettings file from PicoScope where the setup is working in reply to a response on your support case, and we can then compare the settings.


Software Dev. Engineer

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