|Power along with heart rate is the ultimate information
for a cyclist to have. Combine that with almost unlimited memory
and software to download and keep track of the info then you really have
something. The Polar Power kit for the S710, S720i, S725 allows a cyclist to
accurately and conveniently measure power thru a light weight device
that measures chain tension and speed and then transmits that data to
the S710, S720i, S725 watch.
How It Works
Power = chain tension or force X chain speed
All the power is transferred to the wheels via the chain. The polar power kit measures the chain speed from a sensor at the derailleur pulley and the the chain tension is measured by an infrared device that notices chain movement and vibration. This vibration can be converted to chain tension. This technology is similar to the way the fitness test calculates your VO2 Max and the Tanita body fat scales measure you body fat.
You then enter chain length, chain weight and the distance between the bottom bracket axle to the rear wheel axle. The manual will provide info to help you. The S710, S720i, S725 provides a real time readout of power that is accurate to 5 percent. The S710, S720i, S725 also records Power, Cadence, Speed, Heart Rate and Time all you have to do is pedal.
Your pedal stroke provides max power at 3 o'clock and
minimum power at 6 o'clock. The S710, S720i, S725 uses this to calculate the
power produce by each leg and then display that on the watch in percent.
(i.e. 47 percent right, 53 percent left) The cadence sensor provides
a marker to distinguish each leg.
We have developed a special program to predict times on
real cycling courses using the S710, S720i, S725