Jump to content

As of July 17, 2015, the LabJack forums here at forums.labjack.com are shut down. New registrations, topics, and replies are disabled. All forums are in a read-only state for archive purposes.

Please visit our current forums at labjack.com/forums to view and make new posts. To post on the current forums, use your labjack.com login account. Your old LabJack forums login credentials have been retired. There are no longer separate logins for labjack.com and LabJack forums.


Photo

Counting the pulses of photomultiplier


  • Please log in to reply
3 replies to this topic

#1 jauram

jauram
  • Members
  • 2 posts

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

LabJack Support
  • Admin
  • 8677 posts

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):

http://labjack.com/s...uide/appendix-a

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

orestes05
  • Members
  • 6 posts

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

LabJack Support
  • Admin
  • 8677 posts

Posted 22 April 2013 - 09:15 AM

Start here:

https://forums.labja...?showtopic=5437


0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users