private void PQDIFButton_Click(object sender, EventArgs e)
        {
            List<ObservationRecord> observationRecords;

            using (OpenFileDialog dialog = new OpenFileDialog())
            {
                dialog.Filter = "PQDIF Files|*.pqd|All Files|*.*";
                dialog.Title = "Browse PQDIF Files";

                if (dialog.ShowDialog() == DialogResult.Cancel)
                    return;

                if (!File.Exists(dialog.FileName))
                    return;

                // Parse PQDif File Data
                using (LogicalParser logicalParser = new LogicalParser(dialog.FileName))
                {
                    observationRecords = new List<ObservationRecord>();
                    logicalParser.Open();

                    while (logicalParser.HasNextObservationRecord())
                        observationRecords.Add(logicalParser.NextObservationRecord());
                }

                // Convert to common channel format
                m_channels = observationRecords
                    .SelectMany(observation => observation.ChannelInstances)
                    .Where(channel => channel.Definition.QuantityTypeID == QuantityType.WaveForm)
                    .Select(MakeParsedChannel)
                    .ToList();

                // Clear the list box and data chart
                ChannelListBox.Items.Clear();
                DataChart.Series.Clear();

                // Populate the list box with channel names
                ChannelListBox.Items.AddRange(m_channels
                    .Select((channel, index) => string.Format("[{0}] {1}", index, channel.Name))
                    .Cast<object>()
                    .ToArray());

                // Select the first channel in the list
                ChannelListBox.SelectedIndex = 0;

                // Change the title text of the window to show what file the user has open
                m_fileName = dialog.SafeFileName;
                Text = string.Format("PQDIF - [{0}]", dialog.SafeFileName);
            }
        }