straingage

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• multiplexing of the strain gages with the scxi-1001

  I am trying to write a MatLab program that uses the C++ functions.  I managed in the collection of data of an extensometer, but I do not understand how to configure the multiplexing.

  I use a DAQ, SCXI-1600 in a SCXI-1001 chassis with 9 input modules 8 channel universal bridge SCXI-1520.

  I know that the hardware is possible to multiplex all 9 SCXI-1520 for the acquisition of data because we did it in LabView.  I have currently no LabView on my computer.

  My question is:

  How labview use C++ functions to implement this material to record 72 straingage channels.

  That's what my code looks like:

  Clear, clc
  rate = 100
  time = 1

  If ~ libisloaded ('myni')
  DISP ('Matlab: load nicaiu.dll')
  [notfound, warnings] = loadlibrary ("C:\WINDOWS\system32\nicaiu.dll",...)
  "C:\Program NIUninstaller Instruments\Shared\CVI\include\NIDAQmx.h",...
  'alias', "myni")
  end

  cards = 1
  Chans = 8
  taskh (1) = uint32 (1);

  % This is the C++ function called from MatLab-> int32 DAQmxCreateTask ('master', taskh (1))

  [a, b, taskh (1)] = calllib ('myni', 'DAQmxCreateTask', "master", taskh (1))

  chains of % for both channels 0 through 7 on each and SCXI-1520 cards.

  taskchans = {'SC1Mod3 / ai0:7 ',' SC1Mod4 / ai0:7'};

  samples = time * rate;

  chanName = ";
  minV = - 10F-4;
  Discharge = + 10-4;
  excitV = 3;
  gageFactor = 2.09;
  iniBrdgV = 0;
  nomGageR = 350;
  poissonR = 0.3;
  wireR = 0;
  scaleName = ";

  DAQmx_Val_Strain = 10299;
  10065 = DAQmx_Val_FromCustomScale;
  DAQmx_Val_QuarterBridgeI = 10271;
  DAQmx_Val_Internal = 10200;
  DAQmx_Val_Rising = 10280;
  DAQmx_Val_FiniteSamps = 10178;
  DAQmx_Val_GroupByScanNumber = 1;

  % creation of extensometer (virtual) channel

  [c] = calllib ('myni', 'DAQmxCreateAIStrainGageChan', taskh (1), tank (taskchans (i)),...)
  chanName, minV, discharge, DAQmx_Val_Strain, DAQmx_Val_QuarterBridgeI...
  DAQmx_Val_Internal, excitV, gageFactor, iniBrdgV, nomGageR, poissonR...
  wireR, scaleName);

  % set samplerate and number of samples
  for i = 1:cards
  [a, b] = calllib ('myni', 'DAQmxCfgSampClkTiming', taskh (i), cm, rate, DAQmx_Val_Rising,...)
  DAQmx_Val_FiniteSamps, samples)
  end
   
  Disable the trigger for the start of the %
  for i = 1:cards
  [a] = calllib ('myni', 'DAQmxDisableStartTrig', taskh (i))
  end

  % create variables to read data

  readarray1 = Ones (CARDS, Samples);
  readarray1_ptr = libpointer ('doublePtr', readarray1);
  arrayLength = samples;

  sampread = 0;
  sampread_ptr = libpointer ('int32Ptr', sampread);
  void = [];
  empty_ptr = libpointer ('uint32Ptr', Empty);

  Organization and reading raw data
  strain = ones (maps * chans + 1, samples);
  t = 0:1 / rate: time-1/rate;
  Strain(1,:) = t;)

  for i = 1:cards
  [readarray1, sampread, empty] = calllib ("myni', 'DAQmxReadAnalogF64', taskh (i),-1,-1,...)
  DAQmx_Val_GroupByScanNumber, readarray1_ptr, empty_ptr, sampread_ptr, arraylength);
     
  strain (chans * i-(chans-2): chans * i + 1, :) = readarray1;)
  end

  % Stop all tasks

  for i = 1:cards
  [a] = calllib ('myni', 'DAQmxStopTask', taskh (i));
  If a == 0
  fprintf (' slaughter task %s...) OK \n ", tank (j (i)));"
  on the other
  fprintf (' start task %s...) Failed \n ", tank (j (i)));"
  end
  end

  % Clear all tasks

  for i = 1:cards
  [a] = calllib ('myni', 'DAQmxClearTask', taskh (i));
  If a == 0
  fprintf (' task claire %s...) OK \n ", tank (j (i)));"
  on the other
  fprintf (' task claire %s...) Failed \n ", tank (j (i)));"
  end
  end

  It is the General form of my code.

  I tried to do one task per channel, but I can start only one task at a time.

  I tried to use DAQmxSwitchCreateScanList and DAQmxSwitchSetTopologyAndReset.

  -> but I don't know what the name of device for the switch.

  If anyone can explane how all these SCXI-1520 multiplex LabVIEW cards that would help a lot.

  Thank you.

  OK, I found the solution to this problem.

  The SCXI-1600 multiplexes based on which channels have set you up.  I simply add all 72 channels to the taskh (1) with the function DAQmxCreateAIStrainGageChan (...) then my samples are multiplied by the number of channels, I added.