LongJog's posts over the past few weeks about using different heartbeat straps with his GH625-XT watch gave me the idea/motivation to try the same thing and report my results with a heartbeat monitor strap from a different vendor... so here they are:
I've been experimenting over the past 8-10 days by alternating back and forth between 2 different heartbeat monitor chest straps on successive runs, while using my Globalsat GH625-XT watch to pick up and record the data in both cases. The first of the heartbeat-monitor straps that I used is the one that came packaged with my GH625-XT, and the other is one that I already had from an old Oregon Scientific SE212 heartbeat monitor watch. The Oregon Scientific strap is very old, and I used to use it somewhat extensively for a 2 to 3 year span about 6 or 7 years ago, but stopped using it since then and only recently put a new battery in it and started toying with it again in order to test out some things with the GH625-XT watch(in hopes of helping to isolate and troubleshoot the issues many of us are experiencing with the Globalsat heartbeat monitor strap). To begin with, I was very pleased to find out that this old Oregon Scientific heartbeat monitor was even able to sync up and send data to my GlobalSat watch.
From my experiences with the GH625-XT heartbeat monitor strap, I can without a doubt, say that it is very inaccurate... so much so that the data it reports while working out is not accurate enough to actually be useful. There seems to be unexpected huge peaks and dips in my recorded heartbeat with about an average 1.5 minute (generally a range of between 55 and 120 second) interval between one low point, the following unexpected peak, and the next extreme low point. I'm not sure why this seems to be happening, but it does appear to regularly happen mostly on average in 1.5 minute intervals during my runs with the GH625-XT heartbeat monitor. This is all during a workout that was a relatively smooth and consistent pace without any significant hills on my course. I'm a 34 year old runner, and the Globalsat heartbeat strap seems to indicate that my average heartbeat on my runs is between 181 to 185 beats-per-minute for the duration of the entire run, with wild peaks up to 200 and dips down sometimes even to as low as 150 within numerous short (less than 2 minute) time spans. The heart BPM readings do not seem to coincide at all with how I feel during my runs based on my level of physical exertion while using the Globalsat GH625-XT heartbeat monitor strap.
On the runs in which I used my Oregon Scientific heartbeat monitor strap in conjunction with my GH625-XT watch, I got very reasonable and stable results. My heartbeat seems to be where I would expect it to be for my level of physical exertion during the run and the few peaks that I encountered mostly coincided with me going up a large hill or picking up the pace for a few minutes during the run. It seems to indicate an average heartbeat of about 168-171 during most of my runs, with a range of about 165 to 176 for variation between any peaks and dips, except for areas of the runs where I intentionally picked up the pace for a few minutes for the purposes of testing the upper echelons of the heartbeat range during my otherwise consistently-paced run. The heart BPM reading on my watch seems to also accurately reflect how I feel during the run at various points when I pick up the pace slightly while using the Oregon-Scientific heartbeat monitor strap.
Here is a screenshot of my heartbeat results from tonight's run with the Oregon Scientific heartbeat monitor strap on a short 4.05 mile run at a relatively comfortable pace(24 minutes, 26 seconds to complete run) and the curve NOT smoothed. I did intentionally pick up the pace a noticeable amount for about a 70 second stint at about the 11 minute mark of this run to test some higher heartbeat ranges in my data on this run, and also sped it up a little bit for the last 4 minutes of the recorded portion of the run:
And here is the heartbeat plot from another run along the same exact route at a similar but slightly slower pace but using my GH625-XT heartbeat monitor (24 minutes, 44 seconds to complete the run), and the curve NOT smoothed:
I'm going to continue testing back and forth for another few days, but it seems relatively conclusive to me based on my testing that there is a hardware problem with the GH625-XT heartbeat monitor strap.