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Trigger Source

Controls: Trigger Dialog >> Source
Macros: TrigSrc, TrigSrcDec

The 'Source' label appears above a group of four radio buttons selects the Left or Right Input or Output channel to be monitored for a Trigger event. When Decimate is active, however, the 'Source' label turns into a button... see Trigger Source - Decimate Operation below.

The channel you select must be active (as set via the Input or Generator controls) in order to provide a trigger signal, but it does not have to be visible on the display.

A small red square always marks the effective Source button, which may not be the one you selected if that becomes inactive.

If the Source channel becomes inactive (such as if you toggle Input or Generator off, or one of their channels), Daqarta will use an active channel (if any) as the effective Source.

If only one channel is active, that channel will be the effective source no matter what is selected. If only Inputs or Outputs are active (but not both), then these buttons will just act as a Left or Right selector. For example, if both Outputs are active but no Inputs, then setting Left In will have the same effect as Left Out.

Suppose the Generator is supplying Left and Right stimulus signals to your experiment and you are monitoring responses on the Left and Right Input channels. If you have Source set to (say) Left Out and you momentarily toggle the Generator off to see the effect on the input signals, the effective Source (shown by the red indicator) will go to Right In. Then when you toggle the Generator back on, Left Out will again be used, as selected.

Now suppose instead of toggling the Generator off completely, you go the Generator dialog and just toggle off the Left output. In this case, the rule is that the effective Source will be of the same direction (Out, in this case) so it will go to Right Out. Again, when you toggle the Generator Left output back on, the source will return to the selected Left Out.

These buttons are disabled in Gen Sync mode, since the effective source is the Sync system of the Generator.

Trigger Source - Decimate Operation:

When Decimate is active the 'Source' label is replaced by a button marked 'Source Raw' when inactive and 'Source Decimate' when depressed. The button is only enabled in normal Decimate mode or Decimate Envelope mode. In Decimate Demodulate and Decimate Signed modes the button is forced to 'Source Decimate' and disabled.

The channel selection buttons still work as discussed above. Source Raw means that the trigger operation uses the raw, undecimated waveform from the selected channel to determine the trigger point. Source Decimate means it uses the waveform after decimation.

The difference is that decimation acts as a low-pass filter to remove high-frequency components and noise. This can be useful if the raw waveform is noisy. On the other hand, if you are using Decimate mode to view a long, slow response to a narrow transient pulse (for example), Source Raw allows you to trigger on the transient even though it may be filtered from the decimated display.

Macro Notes:

TrigSrc=LI sets Trigger Source to Left Input. Similarly, RI sets Right Input, LO sets Left Output, and RO sets Right Output. Alternatively, you can use numeric values, variables, or expressions instead of mnemonic names:

    0 = LI
    1 = RI
    2 = LO
    3 = RO

Note that if you use a mnemonic in an {\b IF} test, it must be in quotes: IF.TrigSrc="LI".

Note that when Trigger Source controls are disabled in Gen Sync mode, these commands may result in the macro aborting with an error message.

In normal Decimate or Decimate Envelope modes, TrigSrcDec=1 selects Source Decimate and TrigSrcDec=0 selects Source Raw. TrigSrcDec=x toggles the current state. In Decimate Demodulate or Decimate Signed modes the button is disabled (as it is if Decimate is off and only the 'Source' label appears), so the macro will abort with an error message.

When reading, X=TrigSrc sets variable X to the value of Trigger Source actually in use, regardless of which button is selected. Alternatively, X=TrigSrc?B returns the button selected, whether that channel is active or not.

See also Trigger Toggle - Introduction, Trigger Control Dialog


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