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Subject: Re: synchronizing multiple daq boards
Date: Tue, 19 Aug 2008 14:37:01 +0000 (UTC)
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Hi SJ,

The error you're getting about External being ambiguous is
correct. The USB-6251 has several ClockSource values that
begin with External and you have to continue the word with
the one you want. Notice the legal values for the
ConstraintValue of the ClockSource property below.

&gt;&gt; ai = analoginput('nidaq','Dev2')
Display Summary of Analog Input (AI) Object Using 'USB-6251'.
  Acquisition Parameters:  1000 samples per second on each
channel.
                           1000 samples per trigger on each
channel.
                           1 sec. of data to be logged upon
START.
                           Log data to 'Memory' on trigger.
      Trigger Parameters:  1 'Immediate' trigger(s) on START.
           Engine status:  Waiting for START.
                           0 samples acquired since starting.
                           0 samples available for GETDATA.
AI object contains no channels.
&gt;&gt; propinfo(ai,'ClockSource')
ans = 
               Type: 'string'
         Constraint: 'enum'
    ConstraintValue: {'Internal'  'ExternalScanCtrl' 
'ExternalSampleCtrl'  'ExternalSampleAndScanCtrl'}
       DefaultValue: 'Internal'
           ReadOnly: 'whileRunning'
     DeviceSpecific: 0

The documentation explains each of the values.

Hope this helps.
Sherryl


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