Sensor problems

Important note for iPhone 8 users: please ensure that you are using the latest version of Heart Graph (v4.4.2) or higher, which fixes a problem where the iPhone 8 fails to connect to a Bluetooth sensor.

Given the number of possible combinations of model of iPhone, iPad and iPod, different versions of iOS and the many types of heart rate sensor available, sensor connection problems are remarkably rare. However, we understand that when they do occur they’re frustrating, so we’ve collected together our advice on how to solve them.WahooBlueHrSensor

Heart Graph is compatible with Apple Watch, Bluetooth 4.0 sensors, and ANT+ sensors when connected via an external dongle such as the Wahoo Fitness Key. If you are using an Apple Watch as your heart rate sensor, you can either acquire data in real time using the Heart Graph app on your Watch, or import data from the Apple Watch once your workout is complete. For more details, please see this video tutorial. Unfortunately, due to the design of WatchOS it is not currently possible to acquire data from the Watch for real time display on the phone.

There’s no need to ‘pair’ your Bluetooth/ANT+ sensor explicitly with Heart Graph – the first time you start a new workout, the app will automatically connect to the first heart rate sensor it finds. For subsequent workouts, Heart Graph will only try to connect to this sensor (so, for example, if you train in a gym, the app won’t  be confused by other people’s sensors). If you change sensor, have multiple sensors, or find Heart Graph has connected to the “wrong” sensor, you can register up to 4 valid sensors in the Heart Graph settings.

The tips below are for Bluetooth 4.0 connection, although some of the advice will also be applicable to ANT+ connections via the Wahoo Fitness Key.

  1. First of all, ensure the basics are right:
    • Your device has Bluetooth 4.0 support. (Bluetooth 4.0 was first available in the iPhone 4s and the iPad 3; earlier models will not work with Bluetooth 4.0 heart rate sensors.)
    • Bluetooth turned on in the Apple Settings of your device(!)
    • Heart rate sensor battery OK.
    • The sensor must be snug-fitting on your body to maintain good contact as you move.
    • Most sensors detect electrical signals from the heart, and the contacts must be moist for this to work. Particularly in cold climates, you may not sweat enough to keep these moist until some minutes into your workout.
    • Try pairing your sensor explicitly in the Heart Graph settings: first delete any existing sensors that are listed, then tap “Search for sensors”.SearchForPairedSensors
    • Take a look at our Known Issues page to see if there is already a work-around for your particular sensor.
  2. Do other heart rate apps work on the same device?
    • Heart Graph uses software provided by Wahoo Fitness to connect to your sensor – if the Wahoo Fitness or Wahoo Utility apps are working, it is very unusual for Heart Graph to have problems.
    • Some heart rate sensor manufacturers offer the ability to update the firmware on your sensor. For example, for Wahoo sensors, this can be done in the Wahoo Utility app. You should follow any manufacturer instructions for this procedure very carefully.
    • It may help to turn your device off and on again to clear out any Bluetooth cache problems.
  3. Can you see heart rate data in Apple’s Health app?
    • With iOS8 and later, you can now pair a bluetooth heart rate sensor with Apple’s Bluetooth settings, which on an iPhone will store all heart rate data in the Health app. You should be able to see your heart rate changing in real time when viewing the Heart Rate section of the Health app:HeartRate
    • If your sensor will not connect with Health, we recommend you contact your sensor manufacturer for support.
  4. Access heart rate data in real time from Health rather than with a direct connection to the sensor:
    • If you’re still having problems with Heart Graph, but you can see heart rate data with Health (see above), Heart Graph will automatically try to receive data from Health rather than directly from the sensor. To configure access to data in Health, please take a look at our short tutorial video:Health-as-Sensor-(en)Please note that if you are using this option, you must keep Heart Graph as the foreground app on your phone, and keep the screen on during workouts.