NI USB 6221 Counting

[badr.jpg]

Hey everyone,

So we are looking to get an NI USB 6221 for a project. The idea is that we want to use it to read the data coming out of a photon counter (in the form of TTL signals), at a rate of 10mHz. We have tried using the USB 6008 but have realized that it has no timing capabilities, and can not use an external clock.

So our hopes are that the USB 6221 will be able to read the data out of the photon counter with and without an external clock. Is this reasonable? I have looked at the data sheet but would just like to confirm that it can actually do what we want it to do first.

Thanks!

[Kevin_Price]

STOP!

First, you wrote 10 mHz (meaning milli-Hz), but I assume you mean MHz (Mega-Hz).

According to the spec sheet I found for the 6221 (it wasn't specific to the USB version alone), the counter/timers have only a 2-sample onboard FIFO.  This can drastically limit your sustainable data throughput, and even moreso when using USB (as compared to desktop or PCI(e) versions of the same board).

I'd highly recommend you consider a newer technology X-series board (NI 63xx) which have an enhanced feature set over the M-series *and* a 127-sample FIFO for the counters.   Benchmarks posted on the site show dramatic improvement in sustainable throughput.

Further, a desktop board will give even better throughput performance if that matters more than the portability and laptop-compatibility of USB.

-Kevin P