Anyway, it turned out that the speed sensor was not working well, giving intermittent readings and getting distance and speed rather wrong. After some investigation I worked out that the sensor's battery was probably nearly flat, problem is the sensor is not "user serviceable". In other words you throw it away and pay through the nose for a new one. That's bullshit, particularly from a company like Polar.
A quick call to the agents confirmed this. Send it up to us and we'll replace the unit for $$$. Don't they get it? Downtime, the cost of sending the thing backwards and forwards across the country? I'm guessing that they simply use an RFID unit to scan the frequency of your old one, programme a new one and send the new one to you once you shelled out. Bin the old one when all that's wrong is a flat battery.
One of the most useful tools in my workshop is Google. In no time at all I found that these specific sensors are problematic and that you CAN open them and replace the batteries. Admittedly, one needs to use some delicate brute force and a Stanley knife, but voila and it's open. Replace battery (R15.00), increase tension of contact springs (i.e. bend them up a bit). Apply a small amount of Pratley epoxy to re-seal the unit and Josephine's your Uncle. Seal it properly.
|That's it. Battery under the clip on the left. It's a CR 2035. The chest strap uses a CR2025, the CS200 unit uses another CR2035.|
The lesson? Just like the external BB bearings that say "Do Not Disassemble". Stuff 'em.
To be entirely fair to Polar, the rest of the CS200 is a dream. Easy to use, large display, downloads a treat. Even the mounting bracket is cleverly thought out.