Delayed voltage measurement using a start from a TTL pulse (PCI-6251, NI-DAQmx)

[Hohum-hrm]

Hello,

What I need to do: acquire a voltage measurement after a certain delay (order of microseconds) when we observe a TTL pulse, lasting for around 1-100 microseconds. What options do I have for doing thins?

PS. If this problem is solved in some C code example, please point me to the right direction; I browsed through the NI-DAQmx examples, but didn't spot anything like this.

[Hohum-hrm]

Bump. 😞

[Brad_K · Accepted solution]

Hi Hohum-hrm,

The DAQmx ANSI C example Analog In\Measure Voltage\Cont Acq-Ext Clk-Dig Start demonstrates how to use  DAQmxCfgDigEdgeStartTrig() to enable a digital start trigger. It also demonstrates continuous acquisition, external sample clock, and every N samples events; for a simpler starting point, look at Analog In\Measure Voltage\Acq-Int Clk-Anlg Start and try converting it to use digital instead of analog triggers.

However, this will start the acquisition exactly when the trigger occurs, not after a fixed delay. To add a fixed delay between the trigger and the start of the acquisition, use DAQmxSetStartTrigDelay() and DAQmxSetStartTrigDelayUnits(). The NI-DAQmx C Reference Help (which should be on the start menu under National Instruments >> NI-DAQ) lists the valid values for the units property.

Brad

[Hohum-hrm]

Many thanks,, I will inspect this further!