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.

Tags: NI Software

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