How does Polar LOOK Kéo Power measure power and cadence?

Polar LOOK Kéo Power is compatible with Polar CS600CX/CS600/CS500/CS500+ cycling computers.

The power output measurement of Polar LOOK Kéo Power is based on strain gauges. Altogether 8 strain gauges are embedded in each pedal axle; each pedal axle has 2 measuring circuits; and each circuit has 4 strain gauges. The force applied to the pedal bends the axle and causes the strain gauges to lengthen or shorten. This leads to a change in the gauge resistance. The force applied to each pedal can be determined by measuring the change in the resistance and generated power output can be measured when cycling.

The power output measurement is performed simultaneously from both pedals with identical measurement systems. This enables accurate comparison of left and right leg power output. The total power output is the sum of the power outputs of both legs. The right transmitter sends the power output and cadence data from the right pedal to the left transmitter. The left transmitter then sends the power output and cadence data from both pedals to the cycling computer.

Cadence measurement is done with a magnet incorporated into the pedal. For the cadence measurement there is a reed-relay on the pedal axle and a magnet on the pedal body. With each revolution of the crank the pedal body does one complete revolution around the pedal axle which generates a pulse to the electronic circuit associated with the reed-relay. Measuring the time interval between these pulses the cadence can be calculated as rpm (revolutions per minute).