count ttl pulse only over 2 V

[Rhou7]

Hi I have a problem while I was trying to count a ttl pulse by using the DAQ Assistant. The problem may be simple but I just cannot solve that since I am new to LabView.

There is a TTL pulse generated from our APD which is about 30 ns width, 5V. I want to use LabView to do the photon counting. However due to the noise, I would like to set a count limit of 2V, so the software only count the TTL pulse which is greater than 2V. But I cannot do that. There is no option to set the limit.

And our hardware is BNC-2110 and PCIe-6323.

Can someone help me with this? Thanks.

[Hooovahh]

Okay so perform a finite or continous read of your analog input.  Then you can perform a threshold, where all values below 2 become 0.  This can be done many ways but I'd suggest an auto indexing for loop and using a select function in the for loop.  Then you can perform any normal edge detection you normally would to count pulses.

EDIT: Post some code if you can.

[Dennis_Knutson · Accepted solution]

For a counter input, the minimum voltage for a logic one is 2.2 volts - a ttl level. And no, you can't adjust it higher.

[KarenZL]

Hi, I am a chemistry graduate student who is new to LabView. Our group is doing something similar, we want to generate a TTL pulse from our APD, and then use LabView to do the photon counting. Our hardware is USB 6251-BNC. Now we are trying to find a LabView program that we can use, it is really hard for me to design a new one by myself. Since we are doing something similar, I was wondering is it okay for you to give me some advice or maybe I can look at your Vi to get some idea? Your help will be really appreciated. Thanks.