Sapphire Motion Monitor

The Sapphire is the most affordable of APDM’s inertial monitors. They are designed for applications that require durability for long-term recordings during normal daily activities. Sapphires can continuously log data between 16 and 48 hours, depending on its configuration.

Sapphires log high-precision kinematic data from accelerometers, gyroscopes, and magnetometers with a 50 Hz bandwidth at a sample rate of 128 Hz. This enables a much wider range of applications than is possible with actigraphy monitors on the market. The data is easily retrieved any time the Sapphire is placed in a docking station.

The Sapphire Advantage

Better data for better results. Sapphire's state-of-the-art triaxial accelerometer, gyroscope, and magnetometer capture even the most subtle movements.

Hybrid technology. We coupled the battery life and subtlety of an actigraphy monitor, with the sensitivity and precision of an IMU, to create this sensor.

Logging duration. The Sapphire can hold a charge longer than any IMU on the market, with a minimum battery life of 16 hours at a sample rate of 128Hz, and can be adjusted to last as long two days a single charge.

Never loses data. Data is stored on an internal drive for backup or later download – keeping your data safe.

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

Continuous monitoring. The Sapphire's on-board data storage can hold over 30 days (720hrs) worth of data. With over 16 hours of battery life while continuously monitoring.

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

  •   Orientation Estimates

      Static Accuracy (Roll/Pitch)

      Static Accuracy (Heading)

      Dynamic Accuracy

      1.15 deg

      1.50 deg

      2.80 deg

      Sapphire Orientation
  •   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)

      Asynchronous Logging: 16-48 hours

      Sapphire Motion Monitoring
  •   Synchronization Characteristics

      Only Available on Opals or Emeralds

      Wireless Radio

      Frequency Band


      Transmission Range

      Transmission Range

      Nordic Semiconductor nRFL01+ radio, ultra-low power

      2.40-2.48GHz ISM band, adjustable

      ≤10 µs difference, up to 24 Emeralds or Opals

      30m line of sight

      10m indoors

  •   Docking Station

      The docking station is used to configure, charge, and download data from the movement monitors.

      One docking station is sufficient for any amount of Sapphires since synchronization is unavailable on this inertial sensor.

      APDM Docking Station
  •   External Button

      APDM offers an optional button that fits into the data port of any 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

      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™

      Only compatible with Opal™ movement monitors. 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 movement data.

      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 Sapphire 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

      Synchronization is only available on Opals and Emeralds. We offer two methods of monitor-to-monitor 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 difference between the two protocols is the need of an access point. Master sync is used while wirelessly streaming data in real-time, while mesh sync is used while logging kinematic data directly on to the monitors.

  •   Master Synchronization

      Available on Opals. A user should choose this form of synchronization when real-time streaming is desired.

        • Synchronize up to 24 Opals
        • Data synchronized within 10 µs, 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

      Available on Opals and Emeralds. Mesh synchronization takes advantage of the 8Gb onboard storage on our inertial sensors, letting users record from anywhere with multiple Opals/Emeralds, 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

      Available on Opals. 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 Sapphire System

      What you need with the purchase of an Opal

        • Charging Cable (1 for every Sapphire)
        • Docking Station (1 for any amount of Sapphires)
        • Straps (1 for every Sapphire purchased)
        • Motion Studio Software
        • Computer

      Ask us about demos, rentals, or bulk prices!

      APDM Sapphire Movement Monitor





For more technical information about the Sapphire, or other APDM products, please contact the sales department.


Phone: 503-446-4055