trigger level for ext trigger

[RDexter]

Greetings,

I am programming a PXI-5122, using C++, and niScope.lib.

The attribute, NISCOPE_ATTR_TRIGGER_LEVEL, is restricted by the Vertical configuration, based on some formula of +/-50 percent of input range. If external trigger is selected, whose range is +/- 5volts, and the input range, which might be 200mV range, will the setting of +50 resolve to 2.5 volts, or 100mV? The description of this attribute only addresses input range.

Robert

[Jennifer O]

Hi Robert,

The unit on this property is volts. Therefore if you wish to trigger on a +100mV signal, you should set this attribute to "0.1", regardless of whether your analog edge trigger source is one of your channels or the external trigger input.

The condition for the trigger level to be valid is stated as follows:

Trigger Level <= Vertical Range/2 + Vertical Offset
Trigger Level >= (-Vertical Range/2) + Vertical Offset

The vertical range and offset in the above condition refers to the range and offset of the trigger source.  In the case of the NI-5122, the external trigger has a fixed vertical range of 10V (+/-5V) and no offset.  Therefore with the source cofigured as external, you can configure any trigger level from -5V to +5V (even if you are measuring a small signal and have your channel range(s) configured for 200mV).

- Jennifer O.
Product Support Engineer - High Speed Digitizers

[RDexter]

Thank you for the response. Now I can program in confidence.

Robert