Have you ever stopped to consider how chip timing actually works? We get a lot of questions from runners and race directors alike regarding the technology and how it works. For most, it just seems to work and they never really give it much though. As a timer though, we have to spend a lot of time thinking about the technology and how to best deploy it. The interesting thing is that many timers are in the same position as you. They know how to set it up and capture times, but they don't really understand the technology behind it. If you were to ask them to give you an explanation, you would be hard pressed to find many that could give you an explanation beyond describing the simply process of radio frequency and the chip interacting with the antenna.
As a professional timing company, we find this lack of understanding from other timers a little alarming. The technology is actually quite complicated and to be the best at it, it is necessary to understand how it works and the best ways to make use of it. You don't need to know how a combustion engine works to drive a car, or how a CPU works in order to use a computer, but radio frequency identification (RFID) requires a little more knowledge to truly make the best use of it.
There are two types of RFID chips in use today. One is called Active RFID and the other is Passive RFID. Active chips have a battery in them that actually broadcasts a signal to the timing equipment. The timing equipment is then able to read the chip identifier and make use of it. This type of chip is found in very high speed racing such as auto racing or cycling. It is much more expensive though as the chips themselves are quite costly. For most road races, passive RFID is the technology used. The chip you see either on the bib or attached to a shoe is basically dormant until it receives enough electrical energy to wake up and communicate. The way it works is that there is an RFID reader that is broadcasting a signal using antennas built into a ground mat or hanging plate. This radio frequency signal provides enough energy so that a chip is able to charge up and start working. You can think of it like a laptop powering up when the start button is pressed. The chip contains a very small micro-processor that takes the signal from the RFID reader and then begins a handshake with that reader. This handshake consists of the chip identifying itself to the reader with a unique number. The reader then takes that number along with the signal strength it detects from the chip and uses that information to determine how close the chip is to the antenna setup. The reader and timing software then use that information to record the start, split point, or finish time of the chip.
In most cases, the chip will get read by the reader and all is good. If a chip gets damaged for some reason, the chip can fail to read and no time will be recorded. There are also items that can interfere with a chip such as a watch or gps in front of the chip. This can happen when a runner holds their arm up in front of the chip at the finish line to stop their watch. Timing chips also need to be visible to the antenna. This means that the runner needs to be wearing the bib on the front of their body facing the antenna. It can sometimes work when on their back, but there are no guarantees.
Hopefully this will help you understan the technology a little better. The technology is great but as with anything it is not foolproof.
See you at the race!
