Here you can find the technical details for the Firstbeat Bodyguard 2 device.


  • Weight: 24 grams
  • Dimensions: 47 mm x 63 mm x 10.6 mm
  • Cable length: 40 cm


  • Device: PA12 plastic, nickel-plated brass stud
  • Cable: medical grade PVC plastic, nickel-plate brass stud

Battery and Storage

  • Battery life: approximately 144 hours (6 days) in a continuous 24/7 measurement with default settings
    • Battery: rechargeable Li-Poly battery
    • Charge time: approximately 30 - 90 minutes depending on the pre-charge
  • Storage capacity: 128MB, approximately 480 hours (20 days) with default settings

Battery and storage capacity can be checked with the device configuration tool found in compatible Firstbeat software products. Memory can be cleared and the internal clock set with the configuration tool as well.

Default settings

  • Accelerometer: on
    • Sampling frequency: 12.5 Hz
    • Resolution: 8 bit
    • G-scale: 4G
  • Night mode: on
    • Start time: 22:00
    • End time: 06:00
  • Alerts: on
    • Battery charge alert: 10 %
    • Free storage alert: 10 %
  • LED brightness:
    • During normal mode: 60%
    • During night mode: 10 % 

Default settings can be checked and changed with the device configuration tool found in compatible Firstbeat software products. It's not recommended to change the default settings.

Measurement accuracy

  • Measurement accuracy for heartbeat recording: 1 ms (1000 Hz)
  • Measurement accuracy for movement (accelerometer):
    • Sampling frequencies: 200Hz, 100 Hz, 50Hz, 12.5 Hz, 6.25 Hz, 1.56 Hz
    • Resolutions: 8 Bit, 14 bit
    • G-scales: 2G, 4G, 8G

Other details

  • IP classes: 
    • IP52 with the cable connected
    • IP20 without the cable
  • Measurement temperature: +5 - +50 C degrees Celcius
  • Storage temperature: -20 - +60 C degrees Celcius 
  • Data upload directly to Firstbeat Lifestyle Assessment service (via the Uploader Plugin) and to the Sports Team and Individual programs.
  • Data uploading and battery charging is done via the USB port, without additional cables


  • CE-Standards:
    • Product is CE marked and complies with the requirements of Electromagnetic Compatibility (EMC) Legislation: Directive 2004/108/EC.
  • FCC-Standards:
    • Product is tested and complies with the FCC technical standards for digital devices: Class B digital device, FCC Part 15. 
    • The Product produces, operates and may generate electromagnetic radiation that may cause a disruption on radio communication. Disruption free use can not be guaranteed. In case the Product causes disruption on any other devices, the problem may be remediable by relocating the Product. Contact Firstbeat Ltd in case continuous problems noticed. Conditions for the use: (1) Product can not cause detrimental or harmful disruptions (2) Product must process and accept also all of the received disruptions, also the ones that may cause the Product malfunction. Product is FCC certificated. WARNING RELATING TO FCC CERTIFICATION: Any alterations or modifications of any kind of the Product, and not explicitly accepted by the Firstbeat Ltd, may invalidate the right to use the Product in accordance with the FCC certification.

Additional information about the accelerometer

Accelerometer provides measurement data for 3 dimensions (X, Y, Z). When device is attached to a person to correct position, the dimensions are as follows:

  • Dimension X measures acceleration right and left. Right decreases (-), left increases (+).
  • Dimension Y measures acceleration up and down. Up decreases (-), down increases (+).
  • Dimension Z measures acceleration forward and backward. Forward decreases (-), backward increases (+).

About accelerometer data:

Sampling frequency 12,5Hz means 12,5 samples per second for each dimension. So the accelerometer provides three values 12,5 times per second. The G-scale defines the maximal acceleration that is measured. In default mode, if any of the accelerometer dimensions recognizes acceleration of 4G or more, it gives maximal positive or negative value. For instance, if the device would accelerate directly upwards in acceleration of 4Gs (or more), the Y-dimension would give maximal negative value and if it goes downwards, it gives maximal positive value. 

Sample size defines the resolution of each sample. In practice it defines the maximal values each dimension can provide. The 8-bit resolution can provide 2^8 (=256) values, which means that maximal negative value is -128 and maximal positive value is +128. The 14-bit provides more accurate resolution, 2^14 (=16284) values having the range of -8192 - +8192. So, with default settings 4G acceleration would provide value -128 or 128 depending on the direction. With 14-bit setting 4G acceleration would provide either -8192 or +8192. 

Before use

  • Charge the device battery. Battery is charged in a USB port.
  • Adjust the device settings: set the clock and clear the memory

See also these:

Warranty information

How to attach the device

Signal light explanations

Video: Using the Bodyguard 2