PAM and PWM Signal Measurment

[Martin88]

Hi forum,

I am would like to measure a signal that looks like this:

The measurment should give me the low and high state, overshoot as well as rising and falling time of the signal.

I tried to use the  pulse measurment vi it works really well as soon the signal is a PWM signal, but the signal could also stay on just one level for example +12V then i get the zero crossing failure. How would you suggest to measure the signal I may could try to a case structure with two cases crossing zero not crossing?

Thanks 
Martin

[RupiDo]

Hi Martin,

how do you get your signal? Do you acquiring the PAM from hardware or do you get the data as file?

Depending how the data are available you can use different methods. If you are doing post processing ( data are read from a file and analyzed) you might try the Transition Measurements.vi which is located at signal processing/waveform measurements. There you get the overshoot and rising respectivly falling time of the signal.

Kind regards,

rupido

[Martin88]

Hi,

thanks for the answer, I am collection the signal live and would like to trigger on events (rising time exxeeds, overshoot) doing this with transition measurement it works well as soon the Signal is a pwm signal (there i have a zero crossing). 

But same signal would also change the value and could stay on a constant value, there i will not have a zero crossing. Is there a way to ignore the error or that Labview just measure as soon it detects a zero crossing, if there is no more crossing stop the measurment. 

Thanks
Martin

[RupiDo]

Hi Martin,

available functions for measuring the PAM singal is also depending on device driver VIs. Which NI Hardware are you using to acquire the data scope card, RF Signal analyzer?

There are different functions depending on the device.

Kind regards,

rupido

[Martin88]

HI RupiDo,

i am using a NI9220 device with a cDAQ chassis

[RupiDo]

Hi Martin,

if you would a PXI scope card, the device driver VIs provide functions where you can read the rising and falling time of edge. If you are using the NI 9220 DAQmx API is used for configuration and communictation with the HW.

Please send me a sreenshot from the zero crossing failure. You are also able to filter the specific error by using the Clear Error VI. Be aware to check the code before you clear the error.

regards,

rupido