Maximum Trigger Frequency - USB6210

[saadabbasi]

We are considering purchasing a USB-6210 to digitize a waveform. Our main priority is the synchronization with rest of the system via triggers. I understand that the USB-6210 is within 10ns of a trigger signal.

Our goal is to use the trigger as a signal of when to digitize the waveform. What is the maximum frequency that we can trigger the USB-6210?

[Kevin_Price]

1. I don't know all the specs that matter to you, but I'd recommend you at least give consideration to a newer design like the USB-6321.  (I typically prefer desktop boards over USB whenever it's practical, but I'm assuming for now that USB is a requirement for you.)

2.  If you want your DAQ board to digitize a set of samples for each trigger, it will benefit you to use a board that supports retriggered finite analog acquisition.  This would point toward the 63xx X-series family rather than the 62xx M-series.

3. If you want a *single* sample for each trigger, the NI terminology for that situation would be to use that external signal as a *sample clock*.

4. Consider whether you need true simultaneous sampling across multiple AI channels.  This feature will cost you though.  The lower cost boards will be multiplexers that put a known delay between A/D conversions of one channel to the next.  This is often sufficient for many practical applications.

-Kevin P

[Nathan-M]

Generally speaking, when you use an external sample clock you shouldn't exceed the device's own internal maximum. In this case, the device is capable of generating a sample clock of 250 kHz. This is the fastest that you'd be able to 'trigger' the device. (assuming, like Kevin, that a single 'trigger' means to digitize exactly one sample per channel). 

I'll also point out this section to warn you that accuracy decreases as you leave less time for each channel to settle. 

So for example, if you acquire from 8 channels and want each channel to settle to 2 LSB, you must provide 5 us for each channel, or 40 us total. This means that your sample clock must be no faster than 25 kHz. (1/40 us). It's a trade-off with accuracy, channel count, and as always: cost.