DAQ - Digital multimeter data acquisition software

/// <summary>
/// Check settings validity (sample rate, recording time, file) and start data acquisition
/// in separate thread
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void btnStart_Click(object sender, RoutedEventArgs e)
    {
            . . .  
    SystemSounds.Beep.Play();
    btnStart.Background = Brushes.PaleGreen;
 
    // Data acquisition thread
    DAQThread = new Thread(new ThreadStart(DAQmethod));
    // Thread updating GUI should be STA (Single Threaded Apartment)
    DAQThread.SetApartmentState(ApartmentState.STA);    
    DAQThread.IsBackground = true;
    DAQThread.Start();
    Settings.newFile = false;
    }

/// <summary>
/// Configure DMM for selected measurement, acquire and write data to file
/// (running in separate thread)
/// Revisions:
///     2016-02-24 D.A. added:
/// - external trigger support
/// - timing calculation for 50Hz / 60Hz AC power
/// </summary>
public void DAQmethod()
{
    Settings.Abort = false;     // not aborted
 
    try
    {
        Stopwatch stopWatch = new Stopwatch();
 
        Settings.FileHandle = new StreamWriter(Settings.FileName);
 
        // Header
        Settings.FileHandle.WriteLine("* Date and time:" + DateTime.Now);
        Settings.FileHandle.WriteLine("* Instrument:" + Settings.IDN);
        if (Settings.ExtTrigger)
        {
            if (Settings.SampleRate != 0)
                Settings.FileHandle.WriteLine("* External trigger - Sample rate: " + 
                     Settings.SampleRate + " samples/s");
            else
                Settings.FileHandle.WriteLine("* External trigger - 'time' should be determined" + 
                     " from trigger source");
        }
        else
        {
            Settings.FileHandle.WriteLine("* Sample rate: " + Settings.SampleRate + " samples/s");
            Settings.FileHandle.WriteLine("* Recording time: " + Settings.RecTime + " s");
        }
 
        Settings.FileHandle.WriteLine("* Measurement range: " + Settings.MeasurementType + " - " + 
            Settings.MeasurementRange);
        Settings.FileHandle.WriteLine("* -------- DAQ utility by Davor Antonic --------");
        Settings.FileHandle.WriteLine("*");
        Settings.FileHandle.WriteLine("* Data format: [time value] (Tab delimited)");
 
        //Configure the DMM measurement state
        // DC voltage/current range selection
        Settings.Dmm.WriteString("CONF:" + Settings.MeasurementType + ":DC " + 
             Settings.MeasurementRange, true);
        if (Settings.MeasurementType == "VOLT")
        {
            //10MOhm voltage input impedance setting , "ON" sets >10GOhm
            Settings.Dmm.WriteString(Settings.MeasurementType + ":IMP:AUTO OFF", true);
        }
        // Autozero Off
        Settings.Dmm.WriteString("SENS:" + Settings.MeasurementType + ":DC:ZERO:AUTO OFF", true);
        //Set integration time to .02 PLC (400 us at 50 Hz; 333 us at 60 Hz)
        Settings.Dmm.WriteString(Settings.MeasurementType + ":NPLC .02", true);
        CheckDMMError(Settings.Dmm);                                // Check the DMM for errors
 
 
        // Trigger settings
        int totNoSamples = 0;
        if (Settings.ExtTrigger)
        {
            // Set trigger to external and set slope
            if (Settings.UpTrigger) Settings.Dmm.WriteString("TRIG:SOUR EXT;SLOP POS", true);
            else Settings.Dmm.WriteString("TRIG:SOUR EXT;SLOP NEG", true);
 
            Settings.Dmm.WriteString("TRIG:DEL:AUTO OFF", true);    //Turn OFF Automatic trigger delay
            Settings.Dmm.WriteString("TRIG:DEL 0", true);
            Settings.Dmm.WriteString("TRIG:COUN INF", true);    //Set trigger count
        }
        else
        {
            totNoSamples = Settings.SampleRate * Settings.RecTime;
 
            Settings.Dmm.WriteString("TRIG:SOUR IMM", true);        //Set trigger source to internal
            Settings.Dmm.WriteString("TRIG:DEL:AUTO OFF", true);    //Turn OFF Automatic trigger delay
        // Trigger delay: T = delay + Integration time + 0.51ms => Delay = T - 0.51ms - 0.02 / MainFreq
            double delay = 1 / (double)Settings.SampleRate - 0.00051 - 0.02 / Settings.MainFreq;
            string strDelay = delay.ToString(CultureInfo.InvariantCulture);
            Settings.Dmm.WriteString("TRIG:DEL " + strDelay, true);
            // Set trigger count to infinity - requires Firmware version 2.11 or above
            Settings.Dmm.WriteString("TRIG:COUN INF", true);
        }
        CheckDMMError(Settings.Dmm);                            // Check the DMM for errors
 
        // Allow up to 25 seconds for DMM to make readings
        Settings.Dmm.IO.Timeout = 25000;
 
        // Start acquisition
        Settings.Dmm.WriteString("SYST:BEEP", true);            // DMM beep
        Settings.Dmm.WriteString("INIT", true);                 // Start
        // Show progress bar
        Dispatcher.BeginInvoke(new Action(() =>
        {
            if (Settings.ExtTrigger) pbrAcquisition.IsIndeterminate = true;
            else pbrAcquisition.IsIndeterminate = false;
                    pbrAcquisition.Visibility = Visibility.Visible;
                    tbkAcquisition.Visibility = Visibility.Visible;
                    tbkAcquisition.Text = "";
                    btnStart.IsEnabled = false;
        }));
 
        double time, value = 0;
        double totalTime = 0;    // beginning time
 
        // Acquired number of samples
        int noChunks;
        // For external trigger acquisition should be stopped manually
        if (Settings.ExtTrigger) noChunks = Int32.MaxValue; 
        else noChunks = totNoSamples / Settings.ChunkSize;
 
                stopWatch.Start();
        // Acquire requested number of data chunks and check for abort condition
        for (int i = 0; i < noChunks && !Settings.Abort; i++)
        {
            // Acquire and remove chunk from instrument buffer and save to file
            Settings.Dmm.WriteString("DATA:REM? " + Settings.ChunkSize.ToString() + ",WAIT", true);
            //Read the result into a ',' separated array
            Object[] DCVResult = (object[])Settings.Dmm.ReadList(IEEEASCIIType.ASCIIType_Any, ",;");
 
            for (int j = 0; j < Settings.ChunkSize && !Settings.Abort; j++)
            {
                if (Settings.SampleRate == 0) time = 0;
                else time = totalTime + (double)(j + 1) / Settings.SampleRate;
                value = Convert.ToDouble(DCVResult[j]);
                // Save chunk to file
                string line = time.ToString(Settings.SampleRate == 0 ? "F0" : "F6", 
                     CultureInfo.InvariantCulture) + 
                     "\t" + value.ToString("F6", CultureInfo.InvariantCulture);
                Settings.FileHandle.WriteLine(line);
 
            }
            Settings.FileHandle.Flush();
 
            // update time
            if (Settings.SampleRate > 0) 
                 totalTime += (double)(Settings.ChunkSize) / Settings.SampleRate;
 
            // Display progress (for internal trigger remaining time; for external trigger elapsed time)
            if (!Settings.ExtTrigger)
            {
                int remainingTime = Settings.RecTime - (int)totalTime;
                double progress = 1 - ((double)(remainingTime) / Settings.RecTime);
                Dispatcher.BeginInvoke(new Action(() =>
                {
                    pbrAcquisition.Value = 100 * progress;
                    tbkAcquisition.Text = "Remaining time: " + remainingTime.ToString() + " s";
                }));
                // Show remaining time at DMM display
                Settings.Dmm.WriteString("DISP:TEXT \"" + remainingTime.ToString() + " s left\n" +
                    value.ToString("F4") + " " + Settings.MeasurementUnit + 
                              "\n\nDAQ by D.A." + "\"", true);
            }
            else    // for external trigger display elapsed time
            {
                Dispatcher.BeginInvoke(new Action(() =>
                {
                    tbkAcquisition.Text = String.Format("Time elapsed: {0:hh\\:mm\\:ss}", 
                     stopWatch.Elapsed);
                }));
                // Show remaining time at DMM display
                Settings.Dmm.WriteString("DISP:TEXT \"" + String.Format("Elapsed: {0:hh\\:mm\\:ss}", 
                     stopWatch.Elapsed) + "\n" + value.ToString("F4") + " " + Settings.MeasurementUnit + 
                                   "\n\nDAQ by D.A." + "\"", true);
            }
        }
 
        // Measurement completed or aborted
        Settings.FileHandle.Close();
 
        // Double beep
        Settings.Dmm.WriteString("SYST:BEEP", true);
        Thread.Sleep(500);
        Settings.Dmm.WriteString("SYST:BEEP", true);
        Settings.Dmm.WriteString("DISP:TEXT \"DONE\"", true);
        Settings.Dmm.WriteString("*RST", true);         //Reset DMM
    }
    catch (Exception e)
    {
        MessageBox.Show("Acquisition error (" + e.Message + ")", "Error", MessageBoxButton.OK, 
             MessageBoxImage.Error);
    }
    finally
    {
        // Hide progress bar
        Dispatcher.BeginInvoke(new Action(() =>
        {
            btnStart.Background = Brushes.LightGray;
            btnStart.IsEnabled = true;
            pbrAcquisition.Visibility = Visibility.Hidden;
            tbkAcquisition.Visibility = Visibility.Hidden;
        }));
    }
}