Pedometer Theory of Operation: How do they work?
Pedometers are devices that count steps as their native form of measurement. All pedometers base their operation on step counting by sensing the impact of a foot with the ground as a step is taken. There are two types of sensors used in pedometers to sense steps.
Most pedometers use a simple pendulum or swing-arm system. This type of system uses a pendulum or swing-arm that makes contact with a post when you take a step, closing the circuit and registering a step in the pedometer. This type of system is very effective as long as it is properly designed. This system is usually referred to as the “movement” of the pedometer, much like the movement of a watch. This movement is what sometimes generates the “click” or “rattle” that you hear when you take a step. The calibration of the movement is what is most important, and this is determined by a number of design factors such as the length of the arm, weight of the arm, post type / position, and tension of the spring that supports the arm. Some pedometers allow you to adjust the sensitivity of the movement, usually with a button or slide that adjusts the tension of the arm support spring (Such is the case with the Omron 105 pedometer). This feature can be helpful for those that understand it, but is generally not necessary on a well designed pedometer movement.
Generally speaking most pedometers you will find in the $10-up retail price range will have a quality movement. Most of the established manufacturers have time-proven movements, that are different, but equally effective. The movement used in all Bodytronics pedometers is a time-proven movement that has proven to be extremely durable and accurate. In additional to the quality swing-arm movement, most Bodytronics pedometers incorporate an electronic filter circuit that prevents most non-step movements from being counted as steps. This filter works in conjunction with the movement to insure very good accuracy from Bodytronics pedometers. This filter is really designed for the all-day wearer, who is concerned about steps being counted while riding in a car, or sitting at their desk at work. In these situations an electronic filter is the only way to eliminate counting false steps.
Don’t be fooled by claims of a superior “internal sensor mechanism” that eliminates non-step movements generated by riding in a car or other non-step movement. All pedometers sense impact, and if you are not electronically filtering non-step impacts, they will be counted as steps!
Some new pedometer designs are using accelerometer technology to sense step impact. These pedometers also sense steps in the same way, by sensing impact as steps are taken. This technology has no moving parts, resulting in quiet, reliable operation. Since it is relatively new, long-term reliability is not really known, but the technology is mature, so reliability should not be an issue. The Omron HJ-112 pedometer uses this technology, which appears to be very effective, considering it was recent ranked #1 by a leading consumer magazine. The Omron HJ-112 uses a pair of electronic sensors along with sophisticated internal circuitry as its foundation for counting steps. The two sensors are placed 90 degrees apart, therefore allowing the pedometer to work equally well in any position. The Omron HJ-112 is the only pedometer that can be placed in a pocket or purse and still give solid results. Currently the only downside to this technology is the size and cost, which will likely improve as the use of this technology becomes more widespread.