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Counting the pulses of photomultiplier

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#1 jauram

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Posted 02 June 2010 - 02:52 AM

Hello, I'm considering whether some of the offered LabJack modules could be capable of counting the pulses of a photomultiplier. It is known that this photomultiplier emits voltage pulses having height 2.0 V and length 30 nanoseconds. I need a device which is capable of counting the pulses at the rate of at least 100,000 per second (and I must be able to regularly read out the number of pulses and reset the counter via API using my own developed software). Any advice is appreciated.

#2 LabJack Support

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Posted 02 June 2010 - 09:43 AM

Our lowest cost device, the U3, has 2 hardware counters that from Appendix B can count up to 8 MHz (0/3.3 volt square wave):


2 problems though: Your signal is only 2.0 volts when high, which is the border of the high-level input threshold, and your pulse is only 30 ns which is a little fast to guarantee it will count. I think you could address both of these with a simple comparator on your signal and some sort of RC between the comparator and the counter input. Just a few components, and we can help further if you go this route.

In software you can read and/or reset the counters whenever you want. In command/response mode it takes about 1 or 4 ms each time, depending on your USB connection. In stream mode you can read the full 32-bit counter up to 25,000 times per second.

#3 orestes05

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Posted 21 April 2013 - 03:53 PM

Can you provide more detail about the comparator and RC? What type of comparator chip might work and is the RC just a resistor in series and capacitor in parallel to ground?

#4 LabJack Support

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Posted 22 April 2013 - 09:15 AM

Start here:


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