I wired a 20 KHz clock signal to my DAQ board(NI PCI-6052E) to synchronize an function generator with DAQ. I use "Acquire N Scans - ExtSCanClk.vi" to control A/D. My question is that, does this exteranl scan clock synchronize with the channel clock? Or how is the channel clock gernerated under external clocking application? Thanks! Thanks.
The channel clock is automatically generated (though you can still control the rate of it). Just in case you don't have it, here is a document that discusses the operation of the channel clock: Using an External Scan Clock
There are many other useful documents that talk about the two clocks. I got them by searching ni.com/support for <+channel +clock>.
You can use the same AI Clock Config VI that you use to setup an external scan clock to make changes to the channel clock.
In case you are interested, there are several reasons you might want to change the channel clock. One is to get round-robin type readings where each channel's time stamp is evenly spaced (even when it wraps from the last channel back to the beginning). Another reason is to minimize the effects of a large input impedance from a transducer (the symptoms often show up in what looks like cross-talk where one channel affects the next).
Hope this helps.
John Nieri Applications Engineer National Instruments
bbj, One more thing - you would probably have gotten more interest for this post in the Measurement Hardware --> Multifunction group since it doesn't have anything directly related to Real-Time Systems.