The Power Meter,
Evolved
Power is more than a number.
Add meaning to your training with
SHIMANO's Force Vector analysis.
While power is important,
a simple output number doesn't give you the full picture.
Understanding how you develop power and finding ways
to improve efficiency can unlock new levels of performance.
SHIMANO's Force Vector feature gives you real-time feedback on your pedal stroke,
providing a more complete picture of your effort.
Visualize
Pedaling
Efficiency
Arrows indicate the direction
and amount of force you're applying to the pedals.
Blue arrows show force
rotating your cranks forward
while red arrows represent force
opposing transmission to the rear wheel.
Force Vector is made
possible
by SHIMANO's expertise
in designing
and manufacturing cranks
When designing power meters,
SHIMANO engineers consider crank structure,
the manufacturing process, materials used,
and how a crank flexes under load.
It's this expertise that allows SHIMANO
to achieve such accurate Force Vector measurement.
Using the latest technology
and SHIMANO's industry-leading knowledge,
the latest SHIMANO power meters
are powerful training tools.
Optimal
sensor placement
SHIMANO power meters contain a total of 24 sensors (12 on each side) in a full bridge configuration*.
To accurately separate the force applied to the cranks in the tangential direction and normal direction, each sensor is positioned at an angle to compensate for crank deformation.
This uniquely-designed sensor increases the precision of measurement and enables Force Vector measurement.
*Full bridge configuration:
A sensor circuit configuration that improves temperature compensation with large sensor output.
Unified
left-right design
Although many power meters over the world
have a separate left-right configuration,
SHIMANO power meters have a unified left-right configuration.
A lithium-ion battery is incorporated inside the spindle
that connects the left and right cranks,
and provides power to the left and right sensors.
Wiring the left and right sensors together
eliminates minor deviations in measurement time
and enables accurate measurement of
power on both sides.
Long-life
battery
Power meters that have a lot of sensors and send a large amount of data have high power consumption. However, SHIMANO power meters achieve low power consumption thanks to a unique circuit configuration. A rechargeable lithium-ion battery enables long-term use while contributing to precision. The EW-EC300 Di2 charging connector is used for charging, making bicycle battery management easier.
| Continuous operation time |  |
|||
|---|---|---|---|---|
| Force Vector | Cycling power | OFF | ||
 |
Force Vector | 70h | 230h | 230h |
| Bicycle power | 230h | 230h | 270h | |
| OFF | 230h | 270h | - | |
SHIMANO power meter characteristics
Power precision
Power cannot be measured directly. Therefore, it has to be calculated from measurements of load and time, using the formula below.
Power (W) = Crank average load per single revolution (N) x 2π x crank length (m) / time required for single crank revolution (sec)
Power measurement error is determined by the accumulation of load measurement error, time measurement error, and crank length variation. In order to reduce these errors and variation, SHIMANO power meters are structurally designed based on a careful examination of crank manufacturing methods. Additionally, thorough quality control measures are applied during manufacturing and calibration. For measuring load, each individual crank is calibrated in the factory before being shipped. Crank length is established in the processing stage, with minuscule variance. For the time measurement, measurement precision is improved with the use of magnets, and at a cadence of 90 rpm, the margin of error is a minuscule ± 0.15%.
SHIMANO power meter calibration
SHIMANO performs calibrations to accurately measure the power even if force is applied in a range of directions.SHIMANO load calibration conditions have been developed exclusively by SHIMANO based on a consideration of the conditions required for bicycle power meters, and with reference to JIS B 7728 and ISO 376 standards. Calibration is performed for a combined error of ± 1.5% or less with respect to the rated load.*
With regard to the rated load, loads of varying direction and size may be applied to multiple points on the pedals depending on conditions, but the standard value is established as 800 N. Calibration is performed based on a consideration of maximum loads, so that errors do not increase even under high-input loads as produced by pro riders. This means that stable power values can be calculated for general riders up to pro riders.
Combined error: At the maximum deviation from a straight line that connects the no-load point and the rated load point on the calibration curve, the combined error includes the following errors.
- Nonlinearity
- Reproducibility
- Repeatability
- Zero error
Calibration is performed in a managed environment at a temperature of 18 to 28°C and a humidity of 35 to 75%.
* For FC-R9100-P/FC-R8100-P, ± 2.0% or less.
Temperature compensation
Operating temperature-10°C to 50°C
Because of the properties of aluminum and strain gauges, the zero-point balance of the gauge changes as the temperature changes. This increases the load measurement error. To compensate for this, with SHIMANO power meters, each and every crank is subject to temperature calibration in the factory. When a 2°C change from the time of the zero offset occurs in the environment temperature, the zero point is automatically adjusted.