The the following Garmin HRM sensors only use ANT+ for communication:
Since the iPhone does not have the hardware necessary to connect to ANT+ devices, the only way to receive a signal from these sensors is to use additional hardware. Heart Graph can connect to the Wahoo Fitness Key for ANT+ sensors, although this is for the old 30-pin iPhone connector.
Note that the Garmin HRM-Dual, which supports both ANT+ and Bluetooth transmission simultaneously does connect to Heart Graph directly.
Heart Graph on iPhone has two different modes, depending on the type of heart rate sensor you are using to measure your heart rate (note that on iPad only Bluetooth sensors are supported). The default mode selection is set when you first launch Heart Graph, but can always be changed at any point in the app settings.
If you’re using an Apple Watch, you should set Heart Graph to be in “Apple Watch” mode:
if you’re using a Bluetooth or ANT+ sensor, you should choose the “BTLE/ANT+” mode:
It’s important to select the correct mode to allow Heart Graph to connect to your chosen sensor – the app will not try to connect to the Apple Watch if you have selected “BTLE/ANT+” mode, and similarly, the app will not try to connect to Bluetooth heart rate sensors if you have chosen “Apple Watch” mode..
If you’re using a Mi Band 2 as your heart rate sensor, you need to take an extra step before recording data with Heart Graph.
Open the Mi Fit app, and start a workout:
This will cause the Mi Band 2 to start collecting frequent, regular heart rate samples (e.g., every 5 seconds), which will then allow Heart Graph to create a smooth graph for your workout.