Multichannel scan at different rates with ext clock

[LVilla]

If I am sampling multiple channels (12) on PCI 6071E and each channel has
a different scan rate, how is this related to using an extenal clock? I know
that if I sample all channels at the sam rate the external scan clock can
initiate one scan of data, but at different scan rates per channel what
happens?

Thanks

LVilla

[tnewton]

You cannot scan channels at different rates.

[LVilla]

Hi tnewton,
The NIDAQ User's manual for PC compatibles v 6.7 states on page 3-32:

Multirate Scanning
Use multirate scanning to scan multiple channels at different scan rates
and acquire the minimum amount of data necessary for your application.
This is particularly useful if you are scanning very fast and want to write
your data to disk, or if you are acquiring large amounts of data and want to
keep your buffer size to a minimum.
Multirate scanning works by scanning each channel at a rate that is a
fraction of the specified scan rate. For example, if you want to scan four
channels at 6,000, 4,000, 3,000, and 1,000 scans per second, specify a scan
rate of 12,000 scans per second and a scan rate divisor vector of 2, 3, 4,
and 12.

The text goes onto say:

NI
-DAQ includes three functions for multirate scanning:

.. SCAN_Sequence_Setup

.. SCAN_Sequence_Retrieve

.. SCAN_Sequence_Demux

Use SCAN_Sequence_Setup to identify the channels to scan, their gains, and
their scan rate divisors. After the data is acquired, use
SCAN_Sequence_Retrieve and SCAN_Sequence_Demux to arrange the data into a
more convenient format.

I would like to know more about this.

Many thanks for your help.

LVilla


"tnewton" wrote in message
news:50650000000500000023410000-999158726000@exchange.ni.com...
> You cannot scan channels at different rates.