Suggestions how to emulate a MCA?

[homunculus87]

Hello.

I would like to know if there is a possibility to emulate a MCA (Multichannel Analyser) with LV and/or NI hardware, because this would be more versatile than the prebuilt MCAs. I would like to count the molecule signals (in form of TTL pulses) which arrive in a certain time intervall. The obvious start would be to use the edge counter but I'm clueless how to use it in this context.

Therefore I'm looking for help, suggestions or examples in order to achieve my aim and I would be glad if someone could recommend suited hardware too.

Any help is very appreciated.

I use LabVIEW 7.1 and 8.6.

[PeterAdelhardt]

Hi,

thanks for posting in the NI forums. As I am unfamiliar with MCAs, could you please enlarge on what specifications and functions you would like to cover with the MCA?

Do you just want to simulate an MCA or build one in hardware? And if so, what NI Software/Hardware do you have access to?

Basically, you would either need fast ADC conversion modules (e.g. C-Series modules or Multifunction DAQ hardware), or counter modules - if you are just interested in event counting. Then you could simply acquire the data in LabVIEW, do required processing and provide a user interface.

Sounds like an interesting application!

Regards

Peter

[homunculus87]

Hi,

Thanks for your answer.

I would like to simulate a MCA not build one in hardware. A MCA should be able to count the number of signals that come in a certain time intervall (the "time bin").

For example, we have a beam of molecules flying over some distance D and each detected molecule creates a TTL pulse in the detector. Now every molecule has a different velocity and therefore needs a different time of flight to reach the detector. So I would like to create, for example, 100k time bins each 100 µs wide and count the molecules that fall into one of those time bins. The fastest molecules will be in one of the first time bins while the slower molecules will be counted in a time bin at the end of the time bin row. A complete measurement over all the time bins is called a "sweep".

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@PaSB wrote:

Then you could simply acquire the data in LabVIEW, do required processing and provide a user interface.

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That's the problem: I do not know how to create something similar to those time bins and count the incoming molecule signals. Simple edge counting just yields all the molecules that occured before taking the sample.

I think, when I have an idea how to program the VI, then I can start to think about the hardware requirements. Currently, I have PCI-6036E, 6534/6535 and an USB-device 6216 at hand.

Regards,

homunculus

[Kevin_Price]

This measurement sounds like the inside-out version of a different one I just replied to you about.  Here you would configure a counter for buffered period measurement using units of "Ticks".  Then feed the molecular pulse signal in as the "source" while feeding a constant 10kHz (or whatever) clock in as the "gate".

I'm not near data acq hw now to check, but I think you'll be digging down into a DAQmx channel property node where the source is probably called "timebase source" and the gate is probably called "input terminal" for period measurement.

You will probably also need to properly set a DAQmx boolean property named "Duplicate Count Prevention."    One setting will allow you to buffer correct measurements of 0 if no molecular pulses happen during a given time bin.  The other setting won't buffer anything at all during that interval, leading to erroneous data.   I don't recall which setting produces which behavior because once upon a time the default was inconsistent across different data acq boards and also flip-flopped through a couple versions of DAQmx.  I always just plan to figure it out through trial-and-error.

-Kevin P