DATA ACQUISITION USING THE BIOPAC DATA SYSTEM

Transcription

1 DATA ACQUISITION USING THE BIOPAC DATA SYSTEM Acquiring Your Data: NOTE: Section A1 to A3 will be done for you before enter the lab. Therefore, the system should be set up and ready to acquire data. It is however, useful to know how to set it up yourself and it is essential you read section A.2. in order to perform the experiments in section D.2. correctly in the skeletal muscle lab. NOTE: Make note of the computer number which you are using to acquire your data. This number will be needed when you try to retrieve your data later for analysis. A.1. Introduction & Getting Started The BIOPAC Data Acquisition System (MP100WSW) will be used in this lab to acquire, edit, analyze, store and retrieve data. The MP100WSW provides the tools to perform certain functions that would not be possible using a chart recorder. From the Windows menu, double click on the AcqKnowledge icon. This will open the program and the AcqKnowledge menu will appear: Figure 1. AcqKnowledge Menu

2 To start a new file, click on File and select New. A new graph window will appear. For example, the file name will include the course number (PHARM, PHE, BME or PSL 372H or PSL 374S), a number indicating the number of the computer being used to record the data and an abbreviation of the lab (e.g. SKM_0000 for the skeletal muscle lab). Figure 2 is an illustration of a sample data acquisition. Identified in this figure are the File name (AcqKnowledge...), Menu Options, Toolbar, Channel Boxes, and Scroll Bars acquired with four different channels recording: Lead 1 ECG, Lead 2 ECG, Respiration and Blood Pressure respectively. Do not concentrate on the details of these graphs. For the purpose of the skeletal muscle lab, you will be using only one channel. Figure 2. The Graph Window: A sample data acquisition from the BIOPAC system.

3 The important featured highlighted in Figure 2 are described below. File Name: Shows the name of the file you are currently working on. ToolBar: List of commands that are frequently used for quick and easy access. Channel Boxes: Shows the numbers of channels used in this acquisition Vertical Scroll Bar: Allows you to move up or down along the y-axis of the selected channel. Moving the box up brings you to higher points on the trace, whereas moving it down brings you to lower points. Horizontal Scroll Bar: Allows you to move to different locations in the record alone the x-axis. this is very useful feature when you want to get to the data already acquired. Dragging the box to the left moves you to earlier points in time, whereas moving the box to the right will display events that occurred closer to the end of the record. Cursor/edit/zoom: Cursor: Selects the mouse pointer to further maneuvers Edit: Selects the bracket tool, which is used for data editing and measuring. Zoom: Allows you to expand a section of the data trace in both directions. Status indicator: Must be green to indicate that the hardware is properly connected and turned on. Start: Click this button to start or stop acquiring data. Channel label areas: Shows the names of each channel in use. Measurement Windows: Shows the selected measurement for a channel. Window Arrows: Enlarges, reduces or minimizes the window.

4 A.2. Opening Channels & Channel Calibration To acquire data, you must first select channels which will acquire data. Select Setup Channels under the MP100 menu. The following window will appear: Figure 3. BIOPAC input channel window. To open a channel, you must check by clicking under Acquire, Plot, and Values of each channel. Active channels should have an X in each of these boxes. Each channel can be labeled by overwriting Analog Input. Choose a name which describes the data (for example in the skeletal muscle lab, Force could be used to represent force of muscle contraction). To calibrate a particular channel, make sure the black dot is beside that channel (i.e. channel A1 in the case of Figure 3) and click on Scaling. The Change Scaling Parameters window as shown in figure 4 will appear.

5 Figure 4. BIOPAC change scaling parameters window. Choose two values which you will use to calibrate the channel. For example, if you are measuring tension, as in the skeletal muscle lab, you may choose 0 and 50 grams. With 0 grams applied to the transducer, click CAL 1 and enter 0 in the Map Value box. Apply 50 grams (weight provided) to the transducer and click on CAL 2. Enter 50 as the corresponding Map Value box. Change the units to grams. In the upper left hand corner of the channel window, there is a - symbol. To return to data acquisition window click on OK. A.3. Setting Up the Acquisition Select Setup Acquisition from the MP100 menu. Click on Save once and select Autosave file. Also, click on Memory and select Disk to ensure that your data is acquired directly onto disk. Enter the duration of the experiment into Total Length. For example, you may want to select 2-3 hours, even though the experiment may not last that long. Double click in the upper left hand corner to close this window. YOU ARE NOW READY TO ACQUIRE DATA. ORGANIZE YOURSELF BEFORE STARTING ACQUISITION. A.4. Stopping and Starting Acquisition Acquiring data is as easy as clicking the start button shown in figure 2. To stop acquiring data, click the same button which has now become the stop button. The acquisition will then be stopped, and the data up to that point will be saved automatically in the file which is currently named at

6 the top of the screen. NOTE: stopping and starting the data acquisition system results in sequentially numbered files being stored. (i.e. SKM_0001.acq, SKM_0002.acq, SKM_0003.acq etc.). The file name will be displayed at the top of the screen. Each time you press start/stop a sequentially displayed at the top of the screen. Each time you press start/stop a sequentially incremented file will be created. This may create a large number of files during the course of the experiment making it difficult to deal with later when you go to printer analyze the data. Therefore, it is best to be organized, avoiding unnecessary stops and restarts which will create a number of files which have no meaningful analysis value (i.e. contain no important data). Avoid clicking on start until you are completely ready to begin or continue with experimental maneuvers. If you start acquiring, but the file contains no important data (i.e. you have started acquiring before you were set up for maneuvers), you may wish to identify that file as an empty file. To do this, you can use the Event Markers as discussed in the next section to insert text which will allow you to identify an empty file. Note: If the system halts or crashes during the course of the experiment and must be rebooted, please consult your T.A. before continuing. A.5. Event Markers It is important to make note of an event during the course of an experiment so it may be referenced later. For example, you may want to note when a treatment began or a drug was injected so you can later examine the effect of the treatment. To activate the markers, select the icon from the tool bar. This opens a line above the data for the insertion of the marker text. Once the even marker feature is activated, you can automatically insert markers during an acquisition by pressing the F9 key. This will insert a marker at that time and will activate the text line so you can enter a comment to be associated with the marker. For example, in the skeletal muscle lab, when you increase the stimulus voltage, you may want to type stimulus voltage increased to. Accessing, Analyzing & Printing Your Data: A.6. Analyzing Data Your data will be saved automatically as it is being acquired. Once the lab is over, it will then be transferred on to the network and will be available in the printing lab in room There will be an

7 announcement made regarding the timing for accessing and printing your data.. You will be able to access the files with a special student account which will only allow you to read, print, or copy data to your own floppy disk. The file will be kept on the network for 6 days after which it will be erased. You can make special arrangements with the network technician to have file available after this period. Logging onto the Network: Your login username will be your course number (PHARM, PHE, BME or PSL 372H or PSL 374S). Your login password will be STUDENT (figure 5) Figure 5. Windows for Workgroups Logon window This account will only allow you to run AcqKnowledge so you can access your data and print it. To run AcqKnowledge program, double click on the AcqKnowledge icon from the system menu, once you have successfully logged on. This will start up the program. Accessing you data: Your data will be stored in a sub-directory name based on the number of the computer you were using in the laboratory. For example, if you were using machine number 1, the sub-directory will be called MP Here you will find the file or files related to your acquisition. To open a file, select Open from the AcqKnowledge File menu. You may have to choose the appropriate sub-directory (ie. MP100-01) from the H-drive to find your file. Select your file by clicking on it, then click on OK. This will open the graph window with your data loaded. Your experimental data file name will be: SKxx0yyy.acq Where xx = machine ( ) and Where yyy = an incrementing number starting with 0000 one for each in the series of files in your experiment. Example: SK = Skeletal Muscle lab, experimental data file 10 from machine 3. These files will be found in H:\MP

8 Please Note: All of the groups in the lab will have the same file names. Therefore, it is important that you remember your machine number so that you can access the right subdirectory. Analyzing your data: To analyze a section of the data, select the I- beam edit tool in the lower right hand side of the graph window (figure 5). This will change the mouse pointer to an I-beam. With this tool, you can select a section of the graph by clicking on one point, and dragging the mouse to the left or right. This highlights the area, and allows you to read values from the measurement windows above the trace (figure 5). You can select from a list of measurements and also decide which channel you will measure from. To select a channel, position the cursor on the channel and click the mouse button. Choose the correct channel from the pop-up menu. The channel numbers in the pop-up menu correspond to the numbers in the channel boxes in the upper left hand corner of the graph window. To select a measurement, position the cursor on the measurement channel and click the mouse button. Choose a measurement from the pop-up menu. A.7. Changing Horizontal Axis (Time Scale) and Vertical Axis (Gain) You can change horizontal and vertical scales, both during the course of data acquisition and after the acquisition is completed. This may help with the analysis of your data. Horizontal Axis (Time Scale) 1. Autoscaling: Selecting the icon from the toolbar automatically scales the horizontal axis (Time) to fit all of the acquired data into a single graph screen, allowing you to view all of the acquired data without scrolling. This may not be very useful for long data acquisitions because it condenses the data considerably.

9 2. Manual Scaling: Click once here, on the time scale The second method of scaling the horizontal axis allows you to select an exact time frame by which you can view your data. Clicking once on the time scale beside the cursor tools brings up a horizontal scaling window. Enter the new time units which you wish to be displayed. For example, you may want to see an event which happened very quickly in the data acquisition. In that case, you would select a small time scale of 5 seconds/division. Or, you may wish to observe an event which occurred over a longer period of time and would thus select a scale of 30 seconds/division, or 1 minute/division. Vertical Axis (Gain) 1. Autoscaling : Selecting the icon from the toolbar automatically scales the vertical axis to fit all data points currently in view. If you are acquiring on more than one channel, this applies only to the channel which is currently selected. If you change the horizontal scale or scroll to a different time point in the trace, after autoscaling the vertical scale, you will be required to autoscale the vertical axis again to view the all of the data. 2. Manual Scaling: The second way to change to gain of the window is to click on the vertical axis of the channel that you wish to change. This brings up a vertical scaling window. You can then enter new scaling parameters. A.8. Printing Data In some cases, it is important to have a hard copy of the data. AcqKnowledge allows you to produce high resolution plots of graphs. To print a file, make sure that the segment of data which you want to print is in view in the window, and chose Print from the File menu. This will print the contents of the screen on the selected printer. To print the entire file, choose Autoscale Horizontal from the Display menu first. Printing will take place in room 2278.

10 A.9. Saving Data to Floppy Disk Your data on the network will be erased after six (6) days. If you wish to make a copy of the data for your future use (i.e. while studying for your exams), then you will need to copy the data onto your own floppy disk(s). To do this, while in AcqKnowledge, open the file which you wish to save on your floppy disk. Select Save As from the File menu. You will then be prompted to name your file and determine on which drive you wish to save it. Once you have selected the drive appropriate for the floppy disk (a:) which you are using and have named your file, select OK. Your data will be saved onto your floppy under that name with the extension.acq. If you have many files, you may require more than one disk.