Interbike: New Vector power meter from MetriGear

By James Huang, technical editor | Thursday, October 8, 2009 7.00am

The new Vector power meter from Silicon Valley upstart MetriGear is one of the most promising designs we've seen in years. Consider some of the tantalising details:

  • Force is directly measured at the pedals, closer to where it's produced than other power meters
  • The entire system adds less than 50g relative to a non-Vector equipped bike
  • +/- 1.5 percent claimed accuracy is in line with other top units
  • Vector can easily be transferred between multiple bikes with no calibration required

The heart of Vector is a tiny four-sided strain measuring piezoresistive array, one of which is wholly contained inside the standard hollow spindles of a pair of Speedplay Zero pedals. 

The majority of the hardware is permanently sealed inside the spindle, presumably making metrigear's vector resistant to weather:

The only external bits are the similarly tidy rechargeable battery compartment and wireless ANT+ transmitter that attach to the backside of the crankarm – everything else is permanently sealed in the spindle.

The four-sided sensor array – plus the embedded accelerometer – collects information at a rate of 250kHz and allows Vector to resolve the applied force not only into a single one-dimensional scalar value, as do current meters, but also the direction of the applied force.  The accelerometer also allows Vector to display cadence without the need for any additional sensors or magnets.

Only the rechargeable battery pack and wireless ant+ transmitter reside outside of the pedal spindle though even they are similarly tiny:

End users with a compatible ANT+ head will still see just the single 'wattage' figure displayed on their computer as usual but MetriGear will also offer a developer kit to qualified individuals like biomechanics specialists, physiologists and fit experts who will have full access to all of the embedded data.  

That embedded data will include individual left/right power output as well as the magnitude and direction of force – both in plane and out of plane – at every point in the pedal stroke to facilitate research on rider position, efficiency, and training techniques.  All Vector users will get an ANT+ PC dongle that will permit wireless firmware updates when available.

Typical users will only see the usual single wattage output field on their ant+ compatible displays but metrigear will also offer a 'developer kit' that will provide qualified users with far more information:

For now, MetriGear have only partnered with Speedplay – in part due to the system's popularity but also because that's the platform of choice for Vector's inventors and developers. However, Speedplay's upcoming new SYZR pedal supposedly uses the same spindle so off-road riders will soon have access to the Vector power meter as well.

MetriGear say the first units will begin arriving in stores around February or March 2010. In addition to the appealing feature set, suggested retail for the Vector system is relatively reasonable at US$1,000 (approx £630) – including the pair of Speedplay pedals.

Once fully installed, the metrigear vector is barely noticeable on the user's crankarm:

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