Bio 301 - PowerLab

Biological Sciences 300/301, Smith College | Neurophysiology

Appendix: Capturing data with PowerLab and Chart

Updated: March 23, 2009

This brief guide to PowerLab hardware and Chart software is based on the manual, Getting Started with PowerLab. A PDF file of the complete manual is available in the Chart 5 folder (in the Applications folder). All information about the Mac version of Chart appears in Chapter 4, from which the figures below are taken.

Launch Chart by clicking on its icon in the dock. The software will check to see if the PowerLab input box is connected and powered up, and it will warn you if it isn't. A new chart window will appear in which data will be displayed when you record it. The figure below shows the main chart window and some of its major features. In this example, four channels are shown; your window may have from one to eight channels, depending on the preferences preset for your computer.

The illustrations given here are from the manual, Getting Started with PowerLab. The windows on your screen may have fewer features because Chart permits simplification of its menus and toolbars, which may have been done for your computer.

Main Chart Window

Channel Settings

Before you begin recording, you must set certain parameters in the Channel Settings dialog box, which you should activate now from the Setup Menu. Four crucial settings are shown below. Note that the settings in the illustration are not the settings we will use. Our settings are given in the instructions below the figure.

1. First, set the number of channels you wish to make active. Usually this will be 1 or 2 input channels for raw data, and possibly an additional calculation channel for each input channel (for a total of 2 or 4). Do this first. You can add or remove channels later by revisiting the Channel Settings dialog in the Setup menu.

2. Select the sampling rate, the number of points per second that will be digitized for each channel, by activating the drop-down menu for one of the input channels. (Accepting "Same Sampling Rate on All Channels," bottom right, means the sampling rate you choose will apply to all the channels.) 40K is a good choice, and 20K will be satisfactory if you are concerned about the length of files.

"40K" means that 40,000 samples will be taken every second, or 40 every millisecond. This will give very good images of individual spikes when you stretch the time scale to see them.

3. Activate the Input Amplifier dialog box, shown below, by double-clicking on that item for each channel that has raw data input (you must do each one separately). This is the easiest way to set the vertical scale (the "Range"), but it can be done only after you have neural activity to examine.

4. If you wish, select a calculation for any channels that will display data derived from raw input (this can also be done later). An example of a useful calculation is Digital Filtering, using a high-pass filter to remove low-frequency components of the signal (such as slow drift).

Input Amplifier Settings

The Input Amplifier window will show you the raw data coming in on a channel. Select an appropriate voltage range from the drop-down menu to enlarge or reduce the vertical amplitude of the signal so it fits in the display box. This window is also where you should choose "Single-sided" (ie, one signal wire vs. ground for each channel), AC coupling if you are looking at extracellular spikes, and "Mains Filter" to filter out 60-cycle power line interference. Digitally filtering out low-frequency drift is done as a calculation on a channel after you have recorded data, and can be set up later.

When everything is set for this channel, click "OK" and continue with the input settings for any other channels that receive raw data.

Recording Data and Saving Files

After you have established the required settings, you are ready to record data. The "Start" button at the bottom right of the main chart window will begin sampling, with data scrolling across the screen. The button becomes a Stop button after sampling begins.

If you are merely examining the signal but do not wish to keep any of the data, clicking the button to the left of the Start button will cause a red X to appear, indicating that data are not being saved in the computer's memory. (Only the graphics screen is being written to as samples are taken and transiently displayed.) Clicking the button again (the red X vanishes) causes samples to be saved in the computer's memory, recording the data for you to look at after you stop the sampling. (Note that the data are not yet in a file; you need to Save current data (File menu) if you wish to be able to go back to that data on a future occasion.)

Toolbar Icons

The toolbar at the top of the screen has a group of icons for various functions. (Some of these may have been deleted from your copy of Chart.) A particularly useful one is "Zoom Window," which will enlarge any selected region of data from the main chart window and display it in a new window.

If you drag across data on one channel to create a highlight area, only that area will be displayed (in both height and width) in the zoom window.

If instead you drag across the time scale at the bottom of the chart window, you will highlight data on all the channels, each at full height.

Zoom Window

The Zoom Window shows you an enlargement of selected data from the main chart window.

With the buttons at the upper right, you can choose whether data from multiple channels should be overlayed on top of each other, or instead displayed as separate traces (as it is in the main chart window). Usually, you will prefer to "Stack channels separately."

If you drag across data in the zoom window, the display immediately updates to show the selected region at an enlarged scale. Your previous view is not lost, however. The "Selection History" buttons at the bottom right of the zoom window let you move back to previous zoom displays (and forward again).

Chart has many other features, but most of the ones we use frequently have been outlined in this summary.

Text © 2008 by Richard F. Olivo
Figures © 2005 by ADInstruments Pty Ltd

	Biological Sciences 300/301, Smith College \| Neurophysiology Appendix: Capturing data with PowerLab and Chart Updated: March 23, 2009
	This brief guide to PowerLab hardware and Chart software is based on the manual, Getting Started with PowerLab. A PDF file of the complete manual is available in the Chart 5 folder (in the Applications folder). All information about the Mac version of Chart appears in Chapter 4, from which the figures below are taken. Launch Chart by clicking on its icon in the dock. The software will check to see if the PowerLab input box is connected and powered up, and it will warn you if it isn't. A new chart window will appear in which data will be displayed when you record it. The figure below shows the main chart window and some of its major features. In this example, four channels are shown; your window may have from one to eight channels, depending on the preferences preset for your computer.
	The illustrations given here are from the manual, Getting Started with PowerLab. The windows on your screen may have fewer features because Chart permits simplification of its menus and toolbars, which may have been done for your computer.
Main Chart Window
Channel Settings	Before you begin recording, you must set certain parameters in the Channel Settings dialog box, which you should activate now from the Setup Menu. Four crucial settings are shown below. *Note that the settings in the illustration are not the settings we will use.* Our settings are given in the instructions below the figure.

	1. First, set the number of channels you wish to make active. Usually this will be 1 or 2 input channels for raw data, and possibly an additional calculation channel for each input channel (for a total of 2 or 4). Do this first. You can add or remove channels later by revisiting the Channel Settings dialog in the Setup menu. 2. Select the sampling rate, the number of points per second that will be digitized for each channel, by activating the drop-down menu for one of the input channels. (Accepting "Same Sampling Rate on All Channels," bottom right, means the sampling rate you choose will apply to all the channels.) 40K is a good choice, and 20K will be satisfactory if you are concerned about the length of files. "40K" means that 40,000 samples will be taken every second, or 40 every millisecond. This will give very good images of individual spikes when you stretch the time scale to see them. 3. Activate the Input Amplifier dialog box, shown below, by double-clicking on that item for each channel that has raw data input (you must do each one separately). This is the easiest way to set the vertical scale (the "Range"), but it can be done only after you have neural activity to examine. 4. If you wish, select a calculation for any channels that will display data derived from raw input (this can also be done later). An example of a useful calculation is Digital Filtering, using a high-pass filter to remove low-frequency components of the signal (such as slow drift).

Input Amplifier Settings	The Input Amplifier window will show you the raw data coming in on a channel. Select an appropriate voltage range from the drop-down menu to enlarge or reduce the vertical amplitude of the signal so it fits in the display box. This window is also where you should choose "Single-sided" (ie, one signal wire vs. ground for each channel), AC coupling if you are looking at extracellular spikes, and "Mains Filter" to filter out 60-cycle power line interference. Digitally filtering out low-frequency drift is done as a calculation on a channel after you have recorded data, and can be set up later. When everything is set for this channel, click "OK" and continue with the input settings for any other channels that receive raw data.
Recording Data and Saving Files	After you have established the required settings, you are ready to record data. The "Start" button at the bottom right of the main chart window will begin sampling, with data scrolling across the screen. The button becomes a Stop button after sampling begins. If you are merely examining the signal but do not wish to keep any of the data, clicking the button to the left of the Start button will cause a red X to appear, indicating that data are not being saved in the computer's memory. (Only the graphics screen is being written to as samples are taken and transiently displayed.) Clicking the button again (the red X vanishes) causes samples to be saved in the computer's memory, recording the data for you to look at after you stop the sampling. (Note that the data are not yet in a file; you need to Save current data (File menu) if you wish to be able to go back to that data on a future occasion.)
Toolbar Icons	The toolbar at the top of the screen has a group of icons for various functions. (Some of these may have been deleted from your copy of Chart.) A particularly useful one is "Zoom Window," which will enlarge any selected region of data from the main chart window and display it in a new window. If you drag across data on one channel to create a highlight area, only that area will be displayed (in both height and width) in the zoom window. If instead you drag across the time scale at the bottom of the chart window, you will highlight data on all the channels, each at full height.
Zoom Window	The Zoom Window shows you an enlargement of selected data from the main chart window. With the buttons at the upper right, you can choose whether data from multiple channels should be overlayed on top of each other, or instead displayed as separate traces (as it is in the main chart window). Usually, you will prefer to "Stack channels separately." If you drag across data in the zoom window, the display immediately updates to show the selected region at an enlarged scale. Your previous view is not lost, however. The "Selection History" buttons at the bottom right of the zoom window let you move back to previous zoom displays (and forward again).
	Chart has many other features, but most of the ones we use frequently have been outlined in this summary. Text © 2008 by Richard F. Olivo Figures © 2005 by ADInstruments Pty Ltd

Biological Sciences 300/301, Smith College | Neurophysiology

Appendix: Capturing data with PowerLab and Chart

Main Chart Window

Channel Settings

Input Amplifier Settings

Recording Data and Saving Files

Toolbar Icons

Zoom Window