trigger below zero

[iehk1]

Hi,

I use NI-6111 (NIDAQmx) since 2 years to start a test, by triggering over a rising voltage over zero (ca 0.5 V ).
Everything worked fine, until now!
I tried to change this trigger voltage to a value below zero (ca. -0.2 V). It doesn’t work anymore; I can not find any parameter in DAQmx witch limits the Trigger Voltage.

use the following functions:

DAQmxCreateAIVoltageChan( hd, 'Dev1/ai0', '', DAQmx_Val_Cfg_Default,  -5,  5,  DAQmx_Val_Volts,  NULL)

DAQmxCfgSampClkTiming( hd,  '',  SampleRate, DAQmx_Val_Rising,  DAQmx_Val_FiniteSamps, NrOfSamples)

DAQmxCfgAnlgEdgeRefTrig ( hd,  'Dev1/ai0',  DAQmx_Val_Rising,  -0.2,  NrOfPreTrigger)

DAQmxStartTask( hd )

DAQmxReadAnalogF64( hd,  -1,   TimeOut,  DAQmx_Val_GroupByChannel,   @data,   NrOfSamples,  @count,   NULL)

hassan

[RobertH]

hello hassan,

according to the specifications (page 9f) of the 6111, it should not be a problem to trigger on voltages below 0V.
(http://digital.ni.com/manuals.nsf/websearch/A9694D34EF10469386256E3000539747)

kind regards,

robert h
NI germany