Absolut timing/ triggering of CI pulse time

[Teresa85]

Hi,

I am fairly new to NI-DAQmx and trying to measure the length and absolute position of digital pulses (high times and low times) relative to a second trigger signal.

The VI CI Pulse Time allows me to measure the low and high times, but I can not get the absolute timing in relation to the trigger signal. The relevant code part so far is attached below. The generation of the trigger signal is not shown, but working correctly. Nicely visible on the oscilloscope.

I was using CI Period in another situation and I could set the variable CI.CtrTimebaseSrc to my trigger signal in order to only measure during the high of the trigger signal. What is the reason this is not working with CI Pulse Time?

Thank you very much,

Teresa

[Julika]

Hi Teresa,

what exactly do you whant to measure? The pulse width or the period time?

Regards, Julika

[Teresa85]

Hi Julika,

thank you for your response.

I've made a small picture showing the actual measurement signals. On the top there is the trigger signal, which defines the beginning of the measurement (T=0 s) as well as the range of the measurement. (Pulses after the trigger signal should not be recorded, but this could also be done in LabVIEW later. It doesn't  have to happen with DAQmx VIs.) The measurement signal consists of random short pulses. I want to extract the time at which those pulses arrive relative to the rising edge of the trigger signal.

Using "CI Pulse Time" I could extract the length of  high and low of every pulse as an array and by adding these values up, I had the time between the measurement pulses. Sadly I could not get the pulse positions in relation to the trigger. Thats why I need to somehow trigger the measurement of "CI Pulse Time".

Maybe there is an easier way to program what I want to achieve that I dont know of?

Thank you,
Teresa

[Julika]

Hi Teresa,

Did you try to use CI Two Edge Seperation? See the following Link:

Counter Input:Measurement Types Property - DAQmx - Data Acquisition VIs and Functions - National Instruments
http://zone.ni.com/reference/en-XX/help/370469AA-01/daqmxprop/attr2fda/

Regards, Julika