analog trigger rate

[TroyF]

I have a USB-6259.  I have a digital trigger (3.3V high, 10 us long, external source) that I am using to control a multichannel acquisition using 9 analog inputs on the USB-6259.  From this trigger, I wish to sample only one measurement from each channel within the shortest time possible (ie, between 1-10 us).  Digital triggers will typically come at a rate of between 1-10 kHz, but the exact timing cannot be known.  Is the 6259 capable of this?  It seems the setup of the trigger is taking quite some time to reset itself for the next trigger and as a result, is missing some triggers.

I have set the Samples Per Second = 100000, and the Number of Samples = 2 (can't seem to do 1).  I am using a digital trigger on PFI0 and triggereing on the rising edge.

[Steven_K. · Accepted solution]

Hi TroyF,

It sounds like your trigger signal can be used as a sample clock. There is an example in the Example Finder that does what you are looking to do. In LabVIEW go to Help»Find Examples... Then select Hardware Input and Output»DAQmx»Analog Measurements»Voltage»Cont Acq&Graph Voltage-Ext Clk.vi. This allows you to select an external source as the sample clock. You would put the trigger signal to a PFI line and select that as the Clock Source.

[TroyF]

This seems to have done the trick. Thanks.  A related question: Following the digital sampling signal, I would like to send a short digital pulse (5 us) on one of the DIO lines.  However, I have noticed that these lines are very slow to update, and cannot output this quickly.  Is there any way around this?

[Steven_K.]

Hi TroyF,

There is an another example that does what you are looking for. You can find it at Hardware Input and Output»DAQmx»Generating Digital Pulses»Gen Dig Pulse-Retriggerable.vi. Your Trigger Source would be the PFI line that you chose for your sample clock. This VI allows you to generate a pulse after a rising or falling edge for a user specified amount of time.