Mobility Lab is typically used in the wireless streaming mode of operation. This is optimal for brief, clinical assessments, but may not be for long IWalk recordings where the subject may be out of range of the access point for some time. Additionally, sometimes it is preferable to record trials "in the field" without the need to bring a computer with you.
To address these needs, Mobility Lab now supports a workflow enabling you to record trials in our Synchronized Logging mode. This mode collects synchronized inertial data without the need for an external access point. Note that data is also logged on the monitors when using the default Robust Synchronized Streaming mode of operation, making this method appropriate for recovering data from some types of wireless failures as well.
Here is a brief rundown of how to take advantage of this new functionality:
To turn on this experimental functionality:
- Click on View->Options in the menu bar and select "Enable logging mode in Mobility Lab (experimental)".
- Restart Mobility Lab
- Navigate to the "Setup" tab
- Click the "Advance" button to show more configuration options.
- In the "Record Mode" combo box, select "Synchronized Logging".
- Double check your monitor assignments.
- Click on the "Apply New Configuration" button to configure the system in Synchronized Logging Mode
- When done, you can test the configuration buy undocking your monitors. At first, their LED patterns will start with a blue flash, indicating that they are not synchronized. The remaining green flashes indicate the battery level, as is the case for the Wireless Streaming mode of operation. Within about 10-15s, the monitors will start blinking in unison and the blue LED flash will stop. Your monitors are now synchronized.
- As soon as the monitors are undocked, they start recording. They continue recording until they are docked again. The trick is to extract the segments of this recording that correspond to the Mobility Lab trials we are attempting to capture.
- There are three ways to identify these segments:
- Button events: The most foolproof way to identify the trial segments is through the use of a button that fits in the port of one of the monitors. The button should be pressed at the beginning and end of the trial. These button events are recorded along with the inertial data and can be used at time of import and conversion to specify the segment corresponding to your trial.
- Wall clock: The monitor's internal clocks are set at configuration time, and should closely match the clock on the computer used for configuration. When a subject performs a trial, note the time (to the second) of the start and end. You should use the clock on the computer used for configuration for this task, or another clock that is set identically or has a known offset. These times will be used when the data is imported and converted into a trial.
- Visual inspection: You can have the subject perform some type of easily identifiable movement indicating the beginning and end of a trial. For example, you can the subject clap 3 times a fixed duration (e.g., 3s) before the start of the trial and after the end of the trial. You can then initially import the complete recording and locate the time stamps of these events by visual inspection of the raw data (in the clapping example, the right and left arm sensors would display 3 sharp peaks at the same time). You would then re-import the trial specifying these time stamps, deleting the original trial when complete.
Import and Conversion:
- After you are done with the recording, you must import the raw data from the monitors and convert them into Mobility Lab trials.
- Dock your monitors.
- Create a new session or select and existing session to add the trial to.
- Go to the "Trials" tab associated with this session.
- Click on the "Import" button.
When you open the import manager, the data from all currently docked monitors are moved to an import directory within the installation folder on your PC. These raw data files are displayed in the table at the top of the import directory. At the bottom of the dialog is a status indicator to help guide you through the conversion process.
- Selecting data for import:
In the table at the top of the Import and Conversion Manager, you select data for conversion by checking the checkboxes of the files you wish to convert.
When you select a file in the table by clicking anywhere on the row, any other files that have overlapping recording times will be highlighted. This functionality aids in finding and merging of data that was recorded on multiple monitors synchronously. You should confirm that recordings from each of your recordings sites (e.g., left arm) are highlighted.
- You can click on the "Select Highlighted" button to select these overlapping recordings.
- Extracting your desired segment:
Recordings logged on different monitors will, in general, not perfectly overlap with each other in the time domain. This is because logging begins as soon as a monitor is undocked and stops as soon as it is docked again. Unless you undock and dock your monitors at exactly the same time, each monitor will log data from slightly different time spans. Using the timestamps or button events generated on each monitor, however, it is possible to extract synchronized data from a group of monitors whose recordings overlap. The Time Range tool will help you extract synchronized data from your logged recordings.
When you select a group of overlapping recordings, the Time Range tool will display the earliest and latest common time within the group. This is the time span for which data is available from all of the selected devices. By default, this is the data that will be converted.
- If the selected files do not overlap temporally, you will not be able to convert the data.
- To crop this recording to correspond to the start times of your trial, click on the "Custom Start Time" checkbox in the "Start Time" panel.
- You can now either specify the start crop time by choosing a time (click on the "Time" button) or a button event (click on the "Marker" button).
- Do the same for the end time.
- In the bottom panel, specify the test type corresponding to this segment and any notes about the trial.
- Click the "Convert" button. Your trial will be added to the selected Session.