To enable you to capture data from Vicon IMUs (Inertial Measurement Units) and optical markers simultaneously, you can use IMUs as digital devices in Nexus to stream and capture data. You can use IMUs to preview data in real time and to capture data onto the IMUs' internal memory. You can then plug the IMUs into your PC via USB and use Nexus to download the captured data.

Before you begin using IMUs with Nexus, note the following points:

• Windows 10 and later only is supported. Ensure the latest Windows 10 updates are installed.
• IMUs have a variety of collection modes, including 15-axes (Acc, Gyro, Mag, HighG Acc, Global Angle):

  

  If Global Angle is selected, the capture rate is 225 Hz. If Global Angle is cleared, the capture rate is 1125 Hz. If HighG only is selected, the capture rate is 1600 Hz.
• Nexus supports the use of up to 18 current Vicon IMUs, dependent on the chosen axes and stream rate.
  For example:
  15 axes (all outputs) at 30 Hz preview rate;
  9 axes at 50 Hz preview rate;
  3 axes at 100 Hz preview rate.
• You can transfer the data that is collected and stored on your IMUs onto your PC using the IMU Transfer pane in Nexus (see Download Vicon IMU data).

For more information, see these topics:

Connect Vicon IMUs to Nexus

For information on the status indicated by the LEDs on the Vicon IMUs, see Understand Vicon IMU status.

Prepare your hardware

1. Ensure that the supplied Bluetooth® (BLE) dongle is plugged into the Windows PC and that its drivers are up-to-date.
2. Ensure your Vicon IMUs are charged and within Bluetooth range.

Connect Vicon IMUs

Nexus enables you to connect Vicon IMUs to Nexus so that you can capture IMU data alongside your optical data.

1. Start Nexus.

2. Select the Vicon IMUs that you want to be detected by Nexus.
   To do this, you modify a list of all available IMUs to select only those that you want to allow to connect.

   To modify the list of allowed IMUs:

   1. In the System Resources tree, right-click Devices.

   2. Click Modify Allow List.

      

   3. In the Allowed Devices dialog box, select only the names of the IMU sensors that you want to connect (to find names from a long list, use the filter with standard wildcards, such as asterisk * and question mark ?), then click Check Selected and click OK.

      

      In the System Resources tree, under Devices, all the Vicon IMUs that you selected in the Allowed Devices list are displayed as connected devices, with a green Play icon next to each IMU name.

      

      When Vicon IMUs are connected into Nexus, in the Properties pane in the Status section, their status is displayed as Connected and the sensor coordinate system is displayed in the bottom right of the 3D Perspective view (if the Global Angle axis is enabled – see Select the required axes).

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      Nexus stores your selection of connected sensors in a configuration file, so that they are remembered when you next use Nexus.
      If you need to add or remove sensors, you must modify the allow list again.

      Tip: If you need to update IMU firmware (indicated by gray icons next to the sensor names in the System tree, and messages in the Log), download and install Vicon Capture.U Desktop and perform the update.

3. To view the settings for a connected IMU, in the System Resources tree, select it.
   Its settings are displayed in the Properties pane, for example, its name, which is initially assigned by Nexus as its serial number (found on the back of the IMU), and battery level.

   

   For more information on the available properties, see Vicon IMU node in the Vicon Nexus Reference Guide.

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   The following example shows IMUs connected to Nexus.

   

   When a Vicon IMU is connected, all available axes stream data:

   • Low-G accelerometer (16 G) (x, y, z)
   • Gyroscope (x, y, z)
   • Magnetometer (x, y, z)
   • Global Angle (x, y, z)
   • High-G accelerometer (200 G) (x, y, z)
     

     

You can now attach the IMUs to the subject and set up and start capture (see Work with Vicon IMUs).

How is Vicon IMU data synchronized to your Vicon system?

Nexus automatically synchronizes your IMU sensor data to your Vicon system so that the IMU data is aligned with the optical data.

Depending on your system setup, IMU data is synchronized in one of these ways:

• If a Vicon Beacon is present in the Nexus system, it is used by default (hard sync).
  If you are using a high number of sensors and/or need a high degree of precision in the synchronization of your data, Vicon recommends that you use hard sync.
  To confirm that the Vicon IMU sensors can automatically detect the Beacon, ensure Prefer Radio Sync is selected in the Properties for the Vicon IMU sensors (this is its default setting):

  

• If no Beacon is present in the system, connection is established via Bluetooth (soft sync).
  If you are using a low number of sensors and/or you don't have a need for precise synchronization of sensor data to optical data (eg, if you're capturing to sensors only), use soft sync. If a Beacon is present in your system, clear Prefer Radio Sync.

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Understand Vicon IMU status

The LEDs on each Vicon IMU display information about its status.

* To enter bootloader mode, hold down the USB adapter button for at least 10 seconds, then release the button. To exit bootloader mode, wait 60 seconds.