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

[afrowizard]

Hello,

The following link is an NI Knowledge Base dealing with generating a retriggerable finite pulse train:

http://digital.ni.com/public.nsf/allkb/204538A044431C9B86257377004EB952?OpenDocument

It deals with gating a continuous pulse train so that you can manually trigger individual pulses, perhaps that will help you. Otherwise, what is the model and brand of the spectrometer/digitizer?

Mason

Applications Engineer

National Instruments

[fjshi]

Hi Mason,

LookslikethisisnottheoneIneed. Thanks very much.

The pulses are preset from the mass spectrometer and I want to manipulate them not generate some new pulses.

The mass spectrometer is a Bruker microTOF and the digitizer is a Agilent U1081A digitizer.

 Jian

[afrowizard]

Jian,

To me it looks like you need to intercept the pulse train, then gate it and send it out again.  Here's an article that discusses gating and triggering in LabVIEW:

http://www.ni.com/white-paper/4329/en/

The first example I showed you was generating a pulse train (which you already have) but it also shows you how to gate that pulse train, which you need to do.