Bike and Byte — Bike Computer Guide | bikeandbyte.com
Speed, cadence, heart-rate and power sensors with units, mounting point and radio.
Speed sensors read wheel revolutions. On a magnet-based setup a spoke magnet passes a fork-mounted sensor and speed equals wheel circumference multiplied by revolutions per second; the 2110 mm circumference for 700x25c must be entered or the reading scales wrong.
Cadence sensors mount on the crank or chainstay and count crank revolutions per minute. A steady club rider pedals at about 80–90 rpm, and head units typically display a 60–100 rpm working band.
Heart-rate sensors are chest straps or arm bands reporting beats per minute. Club riding sits near 120–150 bpm on moderate terrain, with effort pushing toward 180 bpm; the strap pairs over ANT+ or Bluetooth to the head unit.
On narrow screens, swipe or scroll the plate sideways.
Power meters measure pedalling output in watts at the crank, pedal or hub. A steady club rider sustains roughly 100–250 W, and pairing usually includes a calibration step after mounting.
All four sensor types pair over ANT+, the low-power wireless protocol developed by Dynastream Innovations and acquired by Garmin in 2006, or over Bluetooth on units that support it. An ANT+ sensor will not pair with a Bluetooth-only head unit.
Mounting points differ: fork or hub for speed, crank or chainstay for cadence, body for heart rate, crank or pedal for power. Each sensor reports its own unit — rpm, bpm or W — so a screen showing all three is reading three devices.
Further reading