Counting non-TTL pulses

[querty999]

I'm need to count pulses having 2V amplitude, 15ns width (device spec sheet, pg2).  My DAQ board is similar to NI-6356. The NI 6356 spec sheet doesn't say what kind of signals it counts but I assume it's TTL. The 2V pulse amplitude I need to count is below TTL signal level I believe. Is it possible to count these pulses with the 6356? If not, what do I need?

[TCChun]

Hi,

You can use anolog edge trigger to detect voltage level above 2V. However, I'm not sure if a sampling rate of 1.25Ms/s is fast enough to count the pulse.

[querty999]

The first problem is the voltage level (2V). I believe it's too low for counting pulses of this amplitude with the specified NI board, which requires TTL level pulses I think. I've seen references to a device/circuit called a level shifter for adjusting signal levels, but I've never used one and I don't know where to get it. I must be the first person to ever need to count non-TTL pulses. Strangely, the manufacturer rep for the device I mentioned in my original message can't tell me what I need to count the pulses either.

[TCChun]

Hi, There are several method, for example: 1. Amplify the voltage level to TTL level 2. If you are sure that the output voltage is 2V, you can try offsetting the voltage by 0.3V to trigger the minimum high voltage of PXIe 6356 which is 2.2V.

[querty999]

Thanks for the reply. Can you explain how to perform your suggestions?

[crossrulz]

---

@querty999 wrote:

I've seen references to a device/circuit called a level shifter for adjusting signal levels, but I've never used one and I don't know where to get it.

---

Start here: https://www.digikey.com/products/en/integrated-circuits-ics/logic-translators-level-shifters/732