Externally Control Digitizer

[fjshi]

Hi All,

I have a question about how to externally trigger digitizer board of a mass spectrometer. Right now TTL pulses from the mass spectrometer were passed to the digitizer trigger in first and then passed back to the spectrometer to trigger ion optics push ions to the dector and finally another signal line passes the signal back to the digitizer and saved. A schematic diagram was attached here.

I want to take over control of the digitizer not wholely but only trigger the digitizer when I want to save the data. I tried to communicate with the digitizer by myself which will give an error on the software that controls the mass spectrometer because the software thinks the digitizer is missing. So this method fails.

Another way I was trying to do now is to gate these TTL pulses. If I only pass these pulses to the digitizer when I want the data. And meantime I still want to pass the TTL pulses continuously back to the mass spectrometer due to stability issue of the instrument. Does anyone know how to do this? Whant kind of DAQ I need?

I have a NI PCI-6221 along with a SCB-68 Connector Block now.

Thanks very much.

Jian

[Matt_L]

Hi Jian,

It sounds like you would only like to have the digitizer (really, this is just a DAQmx card, I don't want to confuse this with our digitizer products) be triggered in certain cases where you want to save data, but need that trigger to go back into the mass spectrometer always, correct?  I think the easiest way to do this would be to split the trigger signal coming out from the mass spectrometer, first, so that it goes straight to the trigger in of the mass spectrometer as well as the input trigger of the DAQ card.  If you used length matched cables, phase differences in recieving the trigger shouldn't be an issue.  That way, if you only need the DAQ to save the data, you can run the DAQmx application only when you need this.