Polar heart rate monitor troubleshooting
My Polar RS400 heart rate monitor went dead after 2 years of use. Replacing the button battery in the chest strap didn't bring it back to life. Not sure whether the problem originated from the strap or the watch, I went through the verification/troubleshooting process described below.
I connected a sine-wave generator (any wave shape in the 1 to 4 Hz range should work) to the chest unit's snap-on buttons via crocodile clips. As heart rate is measured in beats per minutes (bpm) and there is 60 seconds in each minute, a 1 Hz (1 cycle/s) signal from the generator should result in the watch displaying "60". Likewise, 2 Hz equals "120" and so on. The watch displayed the expected results and so the chest unit is verified to be functioning normally.
I then moved the crocodile clips to the cloth-like electrodes on the elastic band. At this stage, the chest strap failed to communicate with the watch - resulting in "00" being displayed.
The second test led me to suspect that the problem lied in either the electrodes or the snap-on buttons. As an electrode problem held no possibility of repair, I proceeded to inspect the snap-on buttons first. Visually, grunge (likely, sweat residue) has accumulated around and inside the left snap-on button. So, the connection in the snapped-on button has gone high resistance. After the grunge was scraped away with a knife, the heart rate monitor functioned normally again. Yay!
This design flaw crept in after Polar redesigned the chest strap beginning with the RS series. My previous Polars (S610) integrated the electrodes and the chest unit into a one-piece construction and hence obviates the problem of poor connection at the snap-on button joints.
I connected a sine-wave generator (any wave shape in the 1 to 4 Hz range should work) to the chest unit's snap-on buttons via crocodile clips. As heart rate is measured in beats per minutes (bpm) and there is 60 seconds in each minute, a 1 Hz (1 cycle/s) signal from the generator should result in the watch displaying "60". Likewise, 2 Hz equals "120" and so on. The watch displayed the expected results and so the chest unit is verified to be functioning normally.
I then moved the crocodile clips to the cloth-like electrodes on the elastic band. At this stage, the chest strap failed to communicate with the watch - resulting in "00" being displayed. The second test led me to suspect that the problem lied in either the electrodes or the snap-on buttons. As an electrode problem held no possibility of repair, I proceeded to inspect the snap-on buttons first. Visually, grunge (likely, sweat residue) has accumulated around and inside the left snap-on button. So, the connection in the snapped-on button has gone high resistance. After the grunge was scraped away with a knife, the heart rate monitor functioned normally again. Yay!This design flaw crept in after Polar redesigned the chest strap beginning with the RS series. My previous Polars (S610) integrated the electrodes and the chest unit into a one-piece construction and hence obviates the problem of poor connection at the snap-on button joints.
Labels: running
posted by biastee at 9:25 PM
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