Vertical & Trigger coupling

[BABAY]

Hello.

I've got a question concerning coupling configuration on NI-5114. According to the documentation:
Short Name: Trigger Coupling
"Specifies how the digitizer couples the trigger source. This property affects instrument operation only when the Trigger Type property is set to Edge, Hysteresis, Window, or Video. If the trigger source is an input channel, the coupling of that channel is used for the trigger."
Let's consider the case when trigger source is an input channel. Thus, trigger coupling can be one of these:
DC
HF Reject
LF Reject

On the other hand any value from this list should be set to VERTICAL coupling attribute in order to indicate TRIGGER coupling value (see the quoted description)… But obviously I can’t set HF Reject value to vertical coupling.

Could somebody make it clear how all this works?

Regards, Valery.

[BABAY]

From manual for 5114:

Trigger Coupling (Analog Input Channel):
Same as input channel, HF Reject, LF Reject

I guess 'Same as input channel' are:
AC (1 MΩ only),
DC,
GND

Ok. Trying to set Trigger Coupling to AC :
Requested coupling type is only valid when the trigger source is an external trigger channel.

Device: Dev1
Property: Trigger Coupling
Invalid Value: AC
Possible Values: DC, HF Reject, LF Reject

Status Code: -200548

I'm wondering who wrote that manual...

[GRLANDMC]

Hello Valery,

how did you configure the vertical triggering parameter for the 5114?

The trigger coupling parameter works much like the vertical coupling parameter, i.e. the signal is immediately coupled based on the settings for the vertical coupling parameter. Now setting the vertical coupling parameter to AC, the DC components are removed immediately.

Now it should be enough to simply call the 'configure vertical' parameter when using the analog input channels as trigger source.

The error code indicates that there as been a mismatch between these two parameters.

I don't know if I got you right, thus do not hesitate to contact at any time if you have any queueries.

Regards,

C.L. - National Instruments Applications Engineering

[DFGray]

The trigger coupling on the 5114 is functionally independent coupling and filter blocks.  The coupling (AC, DC, GND) is set on the channel the trigger is coming in.  HFRej and LFRej are a separate filter stage.  Unfortunately, the API conflates these concepts, overloading the trigger coupling parameter to mean two separate things, depending on the trigger source.  So, if the trigger is one of the input channels, the trigger coupling can only turn on and off the filter block (DC - no filter, or HFRej or LFRej).  Signal coupling is set by the vertical parameters of the input.  If the trigger is the external trigger, you have the actual AC/DC trigger coupling and the HFRej/LFRej filter all in the same setting.

[BABAY]

Thank you, for the explanations, now it looks mutch more clear to me...

Regards, Valery.