Bike sensors turn your ride data into actionable numbers. A speed sensor tracks how fast you are moving, a cadence sensor counts your pedal strokes, a heart rate monitor measures your effort, and a power meter quantifies your output in watts. Radar sensors add a layer of awareness by alerting you to vehicles approaching from behind. All of these sensors connect to a bike computer or a training app using ANT+ or Bluetooth, giving you real-time feedback and post-ride analysis.
Sensor Types at a Glance
| Sensor | What It Measures | Notes |
|---|---|---|
| Speed sensor | Wheel rotation to calculate speed and distance | Mounts on the wheel hub; user-replaceable CR2032 battery, approximately 12 months at 1 hr/day; stores up to 300 hours of activity data; automatically detects wheel size. |
| Cadence sensor | Crank arm revolutions per minute (rpm) | Attaches to the crank arm; same battery type and life as the speed sensor; data averaging setting available to exclude zero values when you are not pedaling. |
| Heart rate monitor | Heart rate in beats per minute (bpm) | Chest strap worn below the sternum; CR2032 battery, up to 3.5 years at 1 hr/day; water rating 1 ATM (does not transmit while swimming); five heart rate zones based on maximum heart rate. |
| Power meter | Power output in watts; left/right balance; cycling dynamics | Pedal-based systems measure force and cadence; requires calibration; power zones based on functional threshold power (FTP); cycling dynamics show how power is applied through the pedal stroke. |
| Radar | Approaching vehicles from behind | Varia rearview radar improves situational awareness; provides alerts and can enable a green threat level tone; not a replacement for rider attentiveness. |
How Speed and Cadence Sensors Work
According to Garmin’s Edge 530 owner’s manual, the speed sensor mounts on top of the wheel hub with a strap, while the cadence sensor attaches to the inside of the non‑drive‑side crank arm using bands. After two wheel or crank revolutions, the LED flashes green to confirm activity. If no speed sensor is paired, the bike computer uses GPS data to calculate speed and distance. Cadence data from the cadence sensor is always recorded. The manual notes that a non‑zero data‑averaging setting is available for cadence or power; the default excludes zero values that occur when you are not pedaling.
Both sensors use a single CR2032 battery. The Edge 530 manual states that the speed sensor battery lasts approximately 12 months at one hour of use per day, and the sensor can store up to 300 hours of activity data. When the battery is low, the LED flashes red after two revolutions. Replacing the battery involves twisting off the circular cover, waiting 30 seconds, inserting a new battery with the correct polarity, and securing the cover. The speed sensor automatically detects wheel size, but you can manually enter the wheel circumference in the sensor settings if needed.
Heart Rate Monitors
Garmin’s setup guide explains that you should wear the heart rate monitor directly on your skin, just below the sternum, with the module snapped onto the strap and the logos right‑side up. After you put it on, the monitor is active and sending data. The HRM‑Dual uses a user‑replaceable CR2032 battery rated for up to 3.5 years at one hour per day. It carries a water rating of 1 ATM, but the manual notes that it does not transmit heart rate data while swimming.
If heart rate data is erratic, the manual suggests reapplying water to the electrodes, tightening the strap, warming up for 5 to 10 minutes, and wearing a cotton shirt or wetting both sides of the strap. Synthetic fabrics that rub can create static interference. Sources of interference can include strong electromagnetic fields, some 2.4 GHz wireless sensors, high‑voltage power lines, electric motors, ovens, microwave ovens, 2.4 GHz cordless phones, and wireless LAN access points. To care for the strap, the manual advises machine washing it after every seven uses, hanging it or laying it flat to dry, and unsnapping the module when not in use. Replacing the battery requires a small screwdriver (Torx T5, or Phillips #00 for modules produced before September 2020), removing the four screws, waiting 30 seconds, and inserting the new battery positive side up without damaging the O‑ring gasket.
The device uses your user profile to determine five heart rate zones, which are calculated as percentages of your maximum heart rate. The default maximum heart rate is 220 minus your age. Training in certain heart rate zones can help you improve cardiovascular capacity and strength, the manual states.
Power Meters
The Edge 530 and Edge Explore 2 manuals describe Garmin’s pedal‑based power meters, which measure the force you apply a few hundred times every second. They also measure cadence and, because they independently measure left and right leg power, report left‑right power balance (single‑sensing systems do not provide balance). Cycling dynamics metrics show how you apply power throughout the pedal stroke and where on the pedal platform you apply force, including platform center offset.
Before you can use a power meter, you must install it, pair it with your device, and calibrate it. The manual instructs you to keep the power meter active by pedaling until a confirmation message appears. You can set power zones based on your functional threshold power (FTP) in watts or as a percentage of FTP. The device can also estimate your FTP from your user profile, and the manual describes a guided FTP workout with a paired heart rate monitor and power meter for a more accurate value.
Radar Sensors
Garmin’s Edge 530 manual explains that the device can be used with Varia smart bike lights and rearview radar to improve situational awareness. After pairing a compatible radar device, you can enable a green threat level tone that plays when the radar transitions to the green threat level. The manual emphasizes that these products are not a replacement for cyclist attentiveness and good judgment; you must always maintain awareness of your surroundings and operate the bicycle safely. Laws regarding bike lights and helmet use vary by state and city, so check your local regulations before riding. For more on lights and helmets, see our guides on bike lights and helmets.
Pairing Sensors: ANT+ and Bluetooth
Both Garmin manuals state that you should bring the device within 3 m (10 ft) of the sensor and stay 10 m (33 ft) away from other riders’ sensors while pairing. If a sensor has both ANT+ and Bluetooth technology, Garmin recommends pairing using ANT+. After the initial pairing, the bike computer connects to the sensor automatically when you start an activity and the sensor is active and within range.
Zwift’s support page notes that while both ANT+ and Bluetooth Low Energy (BLE) work similarly, BLE tends to give you a stronger signal. Native BLE is the recommended pairing method when possible. For a PC without native BLE, you may need a BLE dongle or the Zwift Companion app as a bridge. If you are using ANT+ sensors with a computer, a USB ANT+ dongle is required, and Zwift suggests using a USB extension cable to place the dongle closer to your equipment to prevent dropouts. On iOS, ANT+ requires a bridge device such as the Viiiiva heart rate monitor or NPE CABLE. For a deeper look at the two wireless standards, read our ANT+ vs Bluetooth for Bike Sensors article.
Using Sensors for Indoor Training
When you ride indoors, the bike computer’s indoor activity profile turns off GPS, so speed and distance data come from a compatible sensor or indoor trainer. The Edge 530 manual describes pairing an ANT+ indoor trainer and using it to set a target power or follow a course. Zwift’s support page explains that if your ANT+ trainer has the Fitness Equipment Control (FE‑C) protocol, it should automatically adjust resistance in‑game. Similarly, a BLE trainer with the FiTness Machine Service (FTMS) protocol provides automatic resistance. When connecting a direct‑drive trainer with ANT+ FE‑C, you must pair the trainer as the power source before connecting resistance or cadence. The Zwift Companion app can also act as a bridge, translating BLE signals so that Zwift can understand them. For help choosing a computer that works with your sensors, visit our Bike Computers category.
Frequently asked questions
Do I need all of these sensors?
No. Many riders start with a speed sensor or rely on GPS for speed and distance. A heart rate monitor adds effort data, while a power meter provides precise training metrics. Radar is a situational awareness aid, not a performance sensor. Choose the sensors that match your riding goals and budget.
How do I replace the battery in my speed or cadence sensor?
Both sensors use a CR2032 battery. The Garmin Edge 530 manual instructs you to twist the circular battery cover counter‑clockwise, remove the old battery, wait 30 seconds, insert a new battery with the correct polarity, and twist the cover back until the marker aligns. The LED flashes red and green after replacement, then green when the sensor is ready.
Can I use my bike sensors with Zwift?
Yes. Zwift supports ANT+ and BLE sensors. For automatic trainer resistance, look for FE‑C (ANT+) or FTMS (BLE) protocols. You may need an ANT+ dongle for a PC or a bridge device for iOS. The Zwift Companion app can also bridge BLE signals.
For more on bike computers that work with these sensors, see our Bike Computers guide.
