I just spoke with Jim from quarq (www.quarq.com) about how their Cinqo bike powermeter picks up and sends power signals to head units. This isn’t covered in their FAQ’s in depth, so I thought I’d post what I understood here:
- The Cinqo reads torque at 60HZ (60 samples a second)
- At each pedal revolution completion the torque values for the rotation are computed to come up with a power figure for the full rotation, using an averaging method rather than a “latest data” method.
- 4 times a second the data from the latest rotation is checked and if there’s a new value (i.e. you just finished a pedal stroke), transmitted via ANT+ to the head unit
You can use the above to go through some scenarios, but the take-home is that when you’re spinning at 90RPM, which is 90/60s = 1.5 rotations a second or a rotation every .67s, you’re generating a new value a little better than every second, and within a 1/4 second of that value being generated, it’s transmitted to the head unit. That means that at worst, the lag between the new value (which is generated every .67 seconds) and the transmission (every .25 seconds) would be limited mostly by the .25 seconds between sends.
The head unit, (mine a Garmin edge 500) on the other hand, is a different matter. Some say that the head unit takes the power measures and just shows, and records, the latest value, which is a bad idea – it should average multiple values in a second, if it receives them, at least for storage purposes, which is widely reported to be 1 measurement stored per second.
On a test ride last night, I saw changes in the head unit that correlate roughly with the above. Tonight I will try to spin up to 200RPM, but am guessing that I’m going to have a hard time reading the display at that RPM to determine if I’m getting faster updates.
There are rumors that head units like an upcoming one from cinqo will show multiple values per second, and that they will also allow for much better data resolution, which may be important for sprinters, or those interested in peak power in general.
The world of sport-focused wrist-top computers, also called watches, jumped ahead light years in the last few months. While I’ve been using a GPS-enabled heart rate monitor for some time now (The Garmin Forerunner 305), it’s huge, and not wearable on a daily basis (see pic @ right on a typical human wrist). The battery life is also not workable – you can’t expect it to stay on for more than 25-30 hours at best, even with the GPS off. But as a training device it’s excellent – tracking where you’ve gone, how fast, how high, and your heart rate along the way.
So Garmin innovates, and uses in the ForeRunner 405 an excellent GPS receiver in a more normal size watch, this time using the closest part of the batch bands as a way to hide the bulk of the watch. It’s still a little large, but a very workable daily war, and includes GPS tracking and heart rate tracking.Â But alas, this thing isn’t the answer to all your prayers. First, it only shows one time zone, which is a drawback in my book. Second, it doesn’t have a barometric altimiter, meaning that you will have to burn major battery to get your altitude, and forget about any baro warnings that a pressure drop is taking place and a storm is coming!
Now Suunto, whose Core device excells in providing Altiture / Baromoter & Compass (ABC), and also sports a depth meter to 32 ft, has out a GPS watch called the X9i, which is not focused on the training world, but rather the navigation world. For instance, the x9i has no heart rate monitor!Â As a matter of fact, Suunto offers *no* watch in all of its lineup that does GPS and a heart rate monitor at the same time as navigation features. You can get a training watch with a GPS pod, and that will help with training, but not with navigation, or get a navigation watch without the HRM!
Suunto’s new X10, which has better battery life than the X9i (lasting 6 hours of GPS monitoring and perhaps as much as a month of non-GPS use as a watch), seems to be the best compromise. In a few words it has: GPS, Altitude, Barometer, Temperature,Compass, and Dual time features.
But here’s the payoff: real integration – as a busy busy guy, I only want to go out, workout, and upload from one device, but I want that device to include the navigation features I need rather than having a performance monitor on one hand, and a navigation device on the other!Â Now only ifÂ these folks realize – it’s really not that much harder to cram a heart rate monitor into this watch – and it would be a *really* smart thing to do. And if they want a beta tester, I’m ready.
So Shame on Suunto and Garmin – why go 80% of the way, then stop, when it really wouldn’t cost much more, or take more battery life, to build the complete package!