#Garmin forerunner 235 troubleshooting skin#
#Garmin forerunner 235 troubleshooting full#

The thing that worries me is that it never behaved like that until a month ago, and I have been using it to record all my activities for a year now. If the known limitations of optical heart rate are simply not acceptable to you and damaging to your training then you should be using a $20 chest strap - the gold standard for HR. If it is a common problem of optical HRM, it is simpy not acceptable. When it gets confused (which can be often) we call this cadence locking.ДЄlso, it is incredibly damaging when you're seeking to reach your personal best and you are not able to monitor your heart properly in the first 3 or 4 kilometers, which to my belief are the ones in which the whole performance is built upon. These two coincidental facts make it extremely hard for the electronic logic in the watch to tell if the 160-spikes-in-luminance-per-minute it's seeing in the data stream is light leaks or heart rate. The issue is that it is perfectly normal for a runners cadence (steps per minute) to be in the 140-180 range, while it is also perfectly normal for a runners heart rate to be in the 140-180 range. Since the watch is not perfectly coupled with the lever its momentum changes at a different rate than your arm an so lags your wrist and so moves on your arm - creating the perfect situation for a brief light leak (to be pedantic the watch is almost always leaking some light, what the shifting causes is a change in the amount leaked) what we've already mentioned is the largest noise source. It is moving quite fast (relatively) and it has sudden momentum changes when your arm changes direction from swinging forward to swinging back (and vise versa). The watch and sensor are on your wrist which is at the far end of a long lever, your arm. It does all sorts of tricks to try and find the signal buried in what is in all actuality a very very noisy data stream.Д«ut consider running. It does not output the raw sensor waveform as HR. It knows that light leakage is real (because Firstbit has extensively tested and modeled the transmitter/sensor/data stream behavior in the real world). Now the electronic logic reading the raw data from the HR sensor knows this. The sensor can not tell the difference between the green component of ambient light and the green that the lights attached to the watch transmit.

#Garmin forerunner 235 troubleshooting skin#

So if the sensor is not tight against your skin ambient light can leak in.

#Garmin forerunner 235 troubleshooting full#

It doesn't have a full spectrum video camera looking, just a very dumb narrow band sensor. So the way optical HR works is by looking for changes in the levels of green light absorbed by the blood.