Analog trigger with time information

[KTChiam]

I am using PXi-6133 to capture analogue signals (8 differential channels) at the rate of 2 MS/s. I am able to capture the data and log into file using TDMS log function. However, processing the data takes too long time as the total data is about 300 MB (for 2 cards / 16 channels, 10 seconds acquisition period).

In order to reduce the amount of data, I am thinking of just sample the data when it is within a range of voltage that I can specify (eg, sample channel 1 when the signal is below 1V), sample channel 2 when the signal is below 1V, etc). I am able to implement analog trigger, but it does not tell me when the event occur (eg, there may be multiple triggers and I need to know when does the trigger happen eg at 1.0001s, 2.1222s etc).

Could anyone shed some light on this?

Thank you.

KT

[niNickC]

Hello KT,

I am unsure how you intend to implement your analogue trigger? This is not possible at a hardware level with DAQmx? You could use software to gate when you log data and then use a get time VI to record when this occurs.

This aside, one suggestion is to read a waveform data type. This will log the waveform start time and include the Waveform increment, from this information the separate trigger times could be calculated.

Let me know your thoughts and if my suggestion is any use.

[KTChiam]

Hi Nick,

The analogue trigger is possible by configuring DAQmx Trigger (Start > Analogue High or Low or Window). I managed to modify from example code, but my application requires to monitor 2 analogue signals to trigger acquisition. When I copy the code and configure to trigger from another channel, it will give me an error.The waveform method works for me.

[niNickC]

Hi,

Sorry but I'm not sure I understand, are you still having an issue or are your problems solved at this point?

[KTChiam]

Hi Nick,

It's partially solved. Anyway, I have some ideas to use additional hardware circuit to solve it. Thanks for your time.

[niNickC · Accepted solution]

Great, no worries, I hope everything goes well.