Photon Counting on 6321

[Adrian_S.]

I am attempting to count photons from 2 photomultiplier tubes (PMT) using Labview. I currently have written a program which will count from a single PMT. I was wondering if the manor in which I wrote the program will reliably count up to 1 MHz, which I believe the card can do, and if it is the best way to write this code. I am relatively new to LabView (esspecially counting).

The program is designed to take a count every 10 - 100 ms and store them for analysis later. I will at somepoint require a program like this to run for up to an hour. It would also be nice if the counter reset evertime instead of reporting the summation of the counts.

Using labview 2012.

Thank you,

A

[Henrik_Volkers]

Your 6321 has a max samplerate of 250kSPS , so if you need to measure your pulse energy and assuming 5 samples per pulse you can go up to 50kHz ....

(less since it's statistic)

And you will need some pulse shaping .... (a 7 step RC,OP buffer chain? )

Since it is a multiplexing card, make shure that your pulse shaping circuit has a low output impedance (more 1Ohm than 50Ohm and close to the DAQ)  (take a look at the settling time error in the spec)

Crosstalk between the channels need to be investigated.

Look at the examples about DAQ streaming TDMS data to file.

Think about a producer-consumer architekture. One loop is reading (producer) and one loop is saving (consumer 1) and two more loops take copied slices of the data to make online monitoring ...

If you just want to count the pulses, you can use the internal counter, up to 1Mhz shouldn't be a problem (again a fast pulse chaper, comparator needed)

[Adrian_S.]

I have a pulse inverter/shaper and disciminator. I primarily just want to count (with the counters) the pulses and wanted to know if there are better ways to write the code than the manor that I did.

Thank you.

A

[John_P1]

I'm still on LV 2011 on this computer so couldn't open your attachment.

If you want the value of the counter to reset after each measurement you could configure a period measurement task like shown below:

Best Regards,

[Adrian_S.]

Sorry for the late response.

Measuring the period wont work. The arrivavale time of the photons to the detector (counts) are random, but the number in a given time period will tell me the the total light signal.

Thank you though.

[falkpl]

I have done this a long time ago.

I had a continious buffered counter on each PMT and in their own loop.  The buffer period wad driven by a 3rd counter generating a clock that controled the count period.  The buffers were written to a functional global (circular buffer for each channel) and processed an a consumer loop.  This way I could bin photons synchronously on multiple channels and process it like a scope without ever losing data.

I later upgraded this and did it in a sbrio so I could make immediate calculations as the photons ariver in real time.

[John_P1]

---

 Measuring the period wont work. The arrivavale time of the photons to the detector (counts) are random, but the number in a given time period will tell me the the total light signal.

---

 This is exactly what my example did--it measures the "period" of the gate signal in terms of number of photons.

Best Regards,

[pitsty]

I tested the code with one PMT and a NI USB-6229. Works perfectly for me. I never considered to use CI PERIOD but used COUNT_Edges and stopped and started the task continiously which is not a good solution to reset the counter. A better approach was to use hardware-timed pause trigger to count photons which unfortunately is not available on USB devices.

[John_P1]

A hardware pause trigger is supported, but not at the same time as using a sample clock on M Series devices