Name: Heart Rate: OHR v strap difference
Rating: 4.5 (22 reviews)
Author: DavidGoneFishing

USAGE NOTE: The current version requires you to view the data field briefly once you have started the activity to trigger the connection to the HR strap. The display will show searching/found and then the HR data. You can then display which ever data field you want then during the rest of the activity. 
 
This datafield compares the optical heart rate data with that from a connected strap and displays the difference along with the heart rates.It should be added as a single field. This based on the Auxiliary Heart Rate app by IMGrant making use of the ANT interface and FITcontributer.

It is specifically built for the Fenix 6 series as I was having large differences between optical and actual HR as the firmware has evolved. By request I've also now added Fenix 5 series devices.

Note that you should not have the external ANT+ heart rate monitor paired to the watch in the usual fashion, the data field will make its own connection. For clarity this means turning the sensor off or removing it under the sensor setting menu.

A complex data field that connects to ANT+ heart rate monitors, displays OHR, strap and delta heart rate (in bpm), and records these into the FIT file, mainly intended to compare with the internal OHR.

Has the ability to set the ANT+ ID of the external heart rate monitor you wish to connect to. Set it to zero (the default) to search for any HRM (it will select the strongest signal, probably, once connected it won't switch to another HRM).

Note that the optical processing delay is unknown. The strap is sampled 4 times per second again with an unknown delay. A datafield can only be updated once per second and hence there maybe a few seconds misalignment of values reported.