AN INTRODUCTION TO CYCLOCOMPUTERS

How It Works

The way a Cycle Computer works is simple. Each time a magnet on the wheel passes a sensor on the fork a signal is generated. The computer measures the time between those signals and works out how fast you're going, based on the wheel dimension you gave it on initial set up.

From that measurement the computer can also work out a whole range of information including distance, average speed, ride time and maximum speed. Depending on the designer's choices it may also have features like auto on/off — pausing the stopwatch when you're stationary — and different types of timing and average speed. You may get average speed only when you're moving, or for the whole ride, and likewise for time. More sophisticated computers may also be able to warn you if you drop below a target average speed or provide an estimate of how long it'll take to arrive at your destination.

Heart rate

Some computers can measure your heart rate by picking up signals from a sensor strapped to your chest. Heart rate is a useful indicator of how hard you're working if you're riding for fitness or, say, to lose weight. Some computers with heart rate function will also provide an estimate of how many Calories you've burned. With rare exceptions, these should be taken with more than a pinch of salt. They are useful for comparing one ride with another, but don't hit the breakfast buffet hard just because a computer says you'd burned off the equivalent of 4 regular breakfasts!

Wired v wireless

In cheaper computers the sensor and handlebar unit are connected with a wire; more expensive computers use a wireless transmitter in the sensor. Wired computers only have one battery to run down, but make your bike look untidy and the wires can get damaged. Wireless computers need a battery in the transmitter as well as the head unit but are tidier and have no wires to snag.

Rear wheel sensor

If you're going to use a computer with a turbo trainer, the magnet and sensor need to read from the rear wheel. Some wired computers won't reach far enough and (more rarely) some wireless units have sensors that won't fit the chain stays.

Water resistance

Cycle Computers will usually keep out heavy rain, but experience shows the level of water resistance varies. Models with altitude functions should not be immersed in water. They need a vent in the case for the altimeter to work, which can let water in. The level of water resistance is indicated by the IP Code, which shows the level of vulnerability to dust and water ingress. Not all manufacturers provide it, but it's a useful guide if they do.

Extra features:

These are common features, typically found on almost every cyclocomputer out there:

• Current Speed
• Average speed
• Maximum Speed
• Cadence
• Maximum cadence
• Ride time
• Time of day.
• Ride/trip distance
• Odometer

Extra features:

Advanced models of Cyclocomputers may have all, or a few, of the following features:

• Heart rate
• Average heart rate
• Maximum heart rate
• Altitude
• Maximum altitude
• Total ascent
• Total descent
• Temperature

Different computers will have different sets of secondary functions that rely on these. These include heart rate zones and targets for training, elevation profile, lap timers, averages and maximums per lap and so on. You may also be able to download ride data from the computer to analyze later.

Smartphone pairing

The latest generation of computers come with apps that wirelessly connect the head unit and your phone. That means as well as its built-in functions, the computer can access your phone's sensors to provide functions such as using Global Position System (GPS, the basis of satellite navigation) to record where you've been. Why not just use an app on your phone? The main advantage of a phone/app combination is battery life. A phone running GPS and screen will drain its battery in a matter of hours. Turning the screen off increases the run time. Another advantage is that instead of being perched on your handlebar, your phone is safely tucked away in a pocket or bag. Computers with smartphone pairing also record data from your ride for later analysis.

GPS

As mentioned above, if you have a smartphone, the cheapest way to get GPS recording is to get a computer that will talk to it. However, if you prefer everything in one box, then you'll need a GPS-enabled computer. Cheaper models use GPS to record where you've been and may have minimal navigation functions, but if you want full sat-nav capability you'll need a more expensive model with a screen large enough to display a map.