How to "Calibrate" data acquired in the live data acquisition example project.

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Connor 2024-1-17

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https://ww2.mathworks.cn/matlabcentral/answers/2071186-how-to-calibrate-data-acquired-in-the-live-data-acquisition-example-project

评论： Connor 2024-1-18

I want the Liveaxes to display the modified sample data but am having problems understanding what math is required to change the recorded data to "calibrate it". I am using the function from the live data aqusition model from the Matlab examples pages and simulating a NI-6001 that is shifting between 10 to -10 V starting from 0. he example works up to when I try to modify the "Calibrateddate" variable.

The variable slopes is in the workspace and has the value 75.460709993827150. There is also an intercept variable I want to include but am unsure of how to add it also, I was wondering about using a loop to change the value of "Calibrateddata" but wasnt sure how to execute the idea.

Thanks.

function scansAvailable_Callback(app, src, ~)
        %scansAvailable_Callback Executes on DAQ object ScansAvailable event
        %  This callback function gets executed periodically as more data is acquired.
        %  For a smooth live plot update, it stores the latest N seconds
        %  (specified time window) of acquired data and relative timestamps in FIFO
        %  buffers. A live plot is updated with the data in the FIFO buffer.
        %  If data logging option is selected in the UI, it also writes data to a
        %  binary file.
            
            if ~isvalid(app)
                return
            end
            
            [data,timestamps,triggertime] = read(src, src.ScansAvailableFcnCount, 'OutputFormat','Matrix');
            %[data,timestamps,triggertime] = readwrite(src, src.ScansAvailableFcnCount, 'OutputFormat','Matrix');
                
            Calibrateddata(:,1) = data(:,1);
            slope = [slopes,1];
            Calibrateddata(:,1) = mtimes(Calibrateddata,slope)
                
            if app.LogRequested
                % If Log data to file switch is on
                latestdata = [timestamps, Calibrateddata]' ;
                fwrite(app.TempFile, latestdata, 'double');
                if timestamps(1)==0
                    app.TriggerTime = triggertime;
                end
            end
           
    
            % Store continuous acquisition data in FIFO data buffers
            buffersize = round(app.DAQ.Rate * app.TimewindowEditField.Value) + 1;
            app.TimestampsFIFOBuffer = storeDataInFIFO(app, app.TimestampsFIFOBuffer, buffersize, timestamps);
            app.DataFIFOBuffer = storeDataInFIFO(app, app.DataFIFOBuffer, buffersize, Calibrateddata(:,1));
            
            
            % Update plot data
            set(app.LivePlotLine, 'XData', app.TimestampsFIFOBuffer, 'YData', app.DataFIFOBuffer);
            if numel(app.TimestampsFIFOBuffer) > 1
                xlim(app.LiveAxes, [app.TimestampsFIFOBuffer(1), app.TimestampsFIFOBuffer(end)])
            end
        end
        
        function Calibrateddata = storeDataInFIFO(~, Calibrateddata, buffersize, datablock)
        %storeDataInFIFO Store continuous acquisition data in a FIFO data buffer
        %  Storing data in a finite-size FIFO buffer is used to plot the latest "N" seconds of acquired data for
        %  a smooth live plot update and without continuously increasing memory use.
        %  The most recently acquired data (datablock) is added to the buffer and if the amount of data in the
        %  buffer exceeds the specified buffer size (buffersize) the oldest data is discarded to cap the size of
        %  the data in the buffer to buffersize.
        %  input data is the existing data buffer (column vector Nx1).
        %  buffersize is the desired buffer size (maximum number of rows in data buffer) and can be changed.
        %  datablock is a new data block to be added to the buffer (column vector Kx1).
        %  output data is the updated data buffer (column vector Mx1).
        
            % If the data size is greater than the buffer size, keep only the
            % the latest "buffer size" worth of data
            % This can occur if the buffer size is changed to a lower value during acquisition
            if size(Calibrateddata,1) > buffersize
                Calibrateddata = Calibrateddata(end-buffersize+1:end,:);
            end
            
            if size(datablock,1) < buffersize
                % Data block size (number of rows) is smaller than the buffer size
                if size(Calibrateddata,1) == buffersize
                    % Current data size is already equal to buffer size.
                    % Discard older data and append new data block,
                    % and keep data size equal to buffer size.
                    shiftPosition = size(datablock,1);
                    Calibrateddata = circshift(Calibrateddata,-shiftPosition);
                    Calibrateddata(end-shiftPosition+1:end,:) = datablock;
                elseif (size(Calibrateddata,1) < buffersize) && (size(Calibrateddata,1)+size(datablock,1) > buffersize)
                    % Current data size is less than buffer size and appending the new
                    % data block results in a size greater than the buffer size.
                    Calibrateddata = [Calibrateddata; datablock];
                    shiftPosition = size(Calibrateddata,1) - buffersize;
                    Calibrateddata = circshift(Calibrateddata,-shiftPosition);
                    Calibrateddata(buffersize+1:end, :) = [];
                else
                    % Current data size is less than buffer size and appending the new
                    % data block results in a size smaller than or equal to the buffer size.
                    % (if (size(data,1) < buffersize) && (size(data,1)+size(datablock,1) <= buffersize))
                    Calibrateddata = [Calibrateddata; datablock];
                end
            else
                % Data block size (number of rows) is larger than or equal to buffer size
                Calibrateddata = datablock(end-buffersize+1:end,:);
            end
        end

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Connor 2024-1-17

I think that I would have to change the value of "data" within the "scansAvailable" function but directly after it is read but am unsure if that is correct.

Connor 2024-1-18