Opal Motion Monitoring

The Opal™ is a miniature, wireless inertial measurement unit that can both log kinematic data and stream it in real-time continuously for over 8 hours. A wireless network of up to 24 Opals is possible, maintaining time-synchronization of ≤1ms between Opals.

Opals use a low-power wireless communication protocol to transmit data to the Access Point, which serves as an antenna for a local computer. Opals have large data buffers to ensure that data is never dropped, even if wireless communication is temporarily interrupted or if the Opal is temporarily out of wireless range.

The Opal Advantage

Never loses data. Even in real-time streaming mode, over 30 days of kinematic data is stored for backup or later download – keeping our data safe.

Long battery life. With over 16 hours of battery life while continuously monitoring, and more than 8 hours while real-time streaming, the Opal can log data throughout the day without interruption.

Use Anywhere. Say goodbye to million dollar research laboratories and video cameras. Opals work in any environment and lighting condition, without occlusion or line-of-sight restrictions. 

Wireless synchronization. Up to 24 Opals exchange data packets to maintain precise time synchronization (≤1ms difference) with, or without, an access point. The Opal is the only inertial sensor on the market that offers both types of synchronization.

Record natural movement. Small, silent, and wireless means the subject will wear it and forget it – recording natural movement all day long.

Real-time Results. Continuously stream data for real-time processing with a latency less than 30ms, perfectly tuned for biofeedback applications.

Powerful tools for custom applications. The APDM™ software development kit includes support for MATLAB™, Java, Python, and C. We provide cross-platform support for Windows, Mac, and Linux.

  •   Sensor Characteristics





      Sample Rate

      Output Rate¹




      3 axes

      ± 2g or ± 6g

      0.0012 m/s²/√Hz

      1280 Hz

      20 to 128 Hz

      50 Hz

      14 bits


      3 axes

      ± 2000 deg/s

      0.05 deg/s/√Hz

      1280 Hz

      20 to 128 Hz

      50 Hz

      14 bits


      3 axes

      ± 6 Gauss

      0.5 mGauss/√Hz

      1280 Hz

      20 to 128 Hz

      50 Hz

      14 bits

      ¹ Adjustable, up to 24 Opals

  •   Orientation Estimates

      Static Accuracy (Roll/Pitch)

      Static Accuracy (Heading)

      Dynamic Accuracy

      1.15 deg

      1.50 deg

      2.80 deg

  •   Hardware Characteristics




      Internal Storage

      Battery Life

      48.4 x 36.1 x 13.4 mm (L x W x H)

      < 22grams (with battery)

      6061 anodized Aluminum, ABS plastic

      8 gb (~720 hours storage)

      Wireless Streaming: 8 hours

      Synchronous Logging: 12 hours

      Asynchronous Logging: 16 hours

      Opal Motion Monitoring
  •   Wireless Characteristics

      Wireless Radio

      Frequency Band

      Data Rate



      Transmission Range

      Transmission Range

      Data Buffer




      Nordic Semiconductor nRFL01+ radio, ultra-low power

      2.40-2.48GHz ISM band, adjustable

      2Mbps on-air data-rate

      300ms (typical) with data buffer

      30ms (typical) without data buffer

      30m line of sight

      10m indoors

      8Gb (~720 hours)

      ≤1ms difference, up to 24 Opals



      ¹ Latency is defined as the time when sample is recorded on the Opal, to the time it is emitted from the host libraries. Our latency includes the hardware, firmware, USB and host library stack.

      ² Both WiFi and Bluetooth use too much energy to be used in small wireless system like the Opal. Our battery life would significantly decrease if we chose to support these wireless protocols, even Bluetooth low energy. Other low power radios, like Zigbee, do not have the bandwidth required to transmit 10 data channels.

  •   Access Point

      The Access Point allows for wireless communication between the host computer and Opal movement monitors, as well as synchronization with external 3rd party hardware. A single access point can support up to 6 Opals, and up to 4 access points can be synchronized to support wireless transmission from up to 24 Opals.

      APDM Access Point
  •   Docking Station

      The docking station is used to configure, charge, and download data from the movement monitors. Docking stations can be chained together to enable synchronization of up to 24 Opals and Emeralds.

      APDM Docking Station
  •   External Button

      APDM offers an optional button that fits into the data port of an undocked monitor. This button allows for additional functionality while recording including:

        • Inserting event markers into the data stream
        • Link to example recording: Click here

      APDM External Button
  •   Straps and Clips

      We offer multiple elastic straps that adjust to fit every body size.

      Strap Types and Recommended Placement

        • Small: Wrist, ankle, hand
        • Medium: Bicep, thighs, forehead
        • Large: Waist
        • Sternum: Chest, back
        • Velcro Pucks: Shoulders, hips
        • Clip: Pocket, belt, shoe laces

      APDM Straps

  •   Motion Studio

      Motion Studio is the default software suite bundled with any APDM movement monitor system. It provides an easy way to get up and running collecting data with your Opals. It also provides advanced configuration, recording, real-time visualization, calibration, and data management features.

      Download Motion Studio User's Manual: Click here

      APDM Motion Studio
  •   Mobility Lab

      Mobility Lab™ is the first portable gait and balance laboratory made for clinicians, researchers, and therapists. It was designed by Dr. Fay Horak to streamline gait and balance assessments by making it easy to collect, store, and analyze data involving human subjects and APDM's wireless Opal inertial sensor.

      For more information about Mobility Lab: Click Here

      APDM Mobility Lab
  •   Software Development Kit

      The software development kit gives users the ability to easily integrate Opal movement monitors into their own applications. The SDK includes support for MATLAB™, Java, Python, and C. We also provide cross-platform support for Windows, Mac, and Linux.

      Download Software Development Kit: Click here

      APDM Motion Studio

  •   Overview

      We offer two methods of Opal-to-Opal time synchronization, master and mesh, as well as the ability to synchronize with third party systems.

      Master synchronization is the most common form of wireless sensor synchronization in the industry, whereas mesh synchronization is unique to APDM. The main difference between the two protocols is the need of an access point. Master sync relies on an access point connected to a local computer to dictate an Opal's time stamp, while mesh sync does not.

  •   Master Synchronization

      A user should choose this form of synchronization when real-time streaming to a local computer is desired.

        • Synchronize up to 24 Opals
        • Data synchronized within 1ms, typical
        • Compatible with third-party systems
        • Access Point required

      APDM Synchronization Methods

      Technical Description

      In a master wireless synchronization scheme, up to 24 Opals in a wireless network transmits kinematic data wirelessly to one or more access point. One of the access points, which is identified during configuration, becomes the master timing source for the entire network. The access point synchronization signal is used to precisely time the transmission of a synchronization data packet. This data packet is transmitted at the exact same time by all access points and is received by all Opals in the wireless network.

  •  Mesh Synchronization

      A user should choose this form of synchronization when off-site recording is desired. Mesh synchronization takes advantage of the Opal's 8Gb internal memory, letting users record from anywhere with multiple Opals, all on the same time stamp.

      APDM is the only company in the industry to offer mesh synchronized inertial measurement units.

      APDM Synchronization Methods

      Technical Description

      In the mesh synchronization scheme, there is no master time source. Instead, each device in the network sends a synchronization packet during its prescribed time slot, enabling each device to compare its clock against the clock of each of the other Opals in the wireless network. This comparison allows each Opal in the mesh to create a statistical model of the network time-a distributed statistical clock model-and of its own clock relative to the network time.

  •   Third-Party Synchronization

      You to easily synchronize your Opal inertial measurement units with third-party systems, such as optical motion capture systems, EMG, or gait mats. Access Points come fitted with a 6 pin digital I/O connector and a 4 pin analog I/O connector.

      We also provide a clock-out signal at 2.56khz, which is used to drive the timing of the entire synchronized system. If fine grained synchronization between systems is necessary, this signal can be used to track the differences in clocking between 3rd party hardware, allowing their data to be precisely correlated.

      Download External Synchronization Sheet: Click here

      APDM Third Party Synchronization

  •   Build your own Opal System

      The highest demanded packages include 3, 6, 10, or 15 Opals, but you can choose to purchase any amount of Opal movement monitors to complete your system. If you need help deciding how many are appropriate for your purpose, please give us a call.

      What you need with the purchase of an Opal

        • Docking Station (1 for every Opal purchased)
        • Access Point (1 for every 6 Opals purchased)
        • Straps (1 for every Opal purchased)
        • Motion Studio Software
        • Computer

      APDM Opal Movement Monitor
  •   3 Opal Package

        • 3 Opal movement monitors
        • 3 Docking stations
        • 1 Access point
        • 3 Body straps (1 waist, 2 ankle)
        • 1 Wireless remote
        • 1 Carrying case
        • 1 Foot template
        • Mobility Lab software
        • 1 Year hardware warranty

      APDM 3 Sensor Kit
  •   6 Opal Package

        • 6 Opal movement monitors
        • 6 Docking stations
        • 1 Access point
        • 6 Body straps
        • 1 Wireless remote
        • 1 Carrying case
        • 1 Foot template
        • Mobility Lab software
        • 1 Year hardware warranty

      APDM 3 Sensor Kit
  •   10 Opal Package

        • 10 Opal movement monitors
        • 10 Docking stations
        • 2 Access points
        • 10 Body straps
        • 1 Wireless remote
        • 2 Carrying cases
        • Motion Studio software
        • Software Development Kit
        • 1 Year hardware warranty

      APDM 3 Sensor Kit
  •   15 Opal Package

        • 15 Opal movement monitors
        • 15 Docking stations
        • 3 Access points
        • 16 Body straps
        • 1 Wireless remote
        • 3 Carrying cases
        • Motion Studio software
        • Software Development Kit
        • 1 Year hardware warranty

      Contact us for package pricing!

      APDM 3 Sensor Kit





For more technical information about the Opal, or any other APDM product, please contact the sales department.

Email:   info@apdm.com

Phone: 503-446-4055