Infrared Heart Rate Monitors
Infrared heart monitors use small infrared sensors lodged into the monitor, usually with a small window cut out to allow infrared beam to pass through. Most models are handheld, with the sensor usually clipped onto a finger or earlobe. In finger detection models, the user places a fingertip over the infrared window, where the infrared sensor detects the blood flowing through the small capillaries present in the finger. Earlobe monitors are usually small rectangular units, the same types installed in exercise machines. They are connected by a small wire to a receiver unit. The pulsing of the blood caused by the heartbeat creates slight disturbances in the infrared beam, which the monitor records and interprets into a numeric heart rate. Earlobe monitors are best used when exercising, because their readings are not affected by the user's movement. However, finger monitors are more effective in dim or poorly lit rooms, because infrared detections can fluctuate in irregular light conditions.
Hand Heart Rate Monitors
Hand Heart Rate Monitors work by detecting the natural electrical signal that triggers the heartbeat.They usually detect these signals from the hands or fingers, where the signal is strong and easy to detect. Most models use two metal sensors, which are touched or grasped with the hand or finger. The monitor records the frequency and intervals of the electrical signals, with each signal synonymous to one heartbeat. They are usually self contained and portable, which makes them ideal to bring while jogging or to share within a group. They can also be mounted permanently on gym walls or exercise machines. They may be inconvenient for some forms of exercise, because they require the hands and arms to be steady while in use. They are also designed for periodic use, which makes them unsuitable for those with medical conditions that need continuous monitoring. In most models, the readout is delayed a few seconds from the actual contact between the finger and the electrode.
Chest Heart Rate Monitors
Chest monitors work much the same way as hand monitors, except that the sensor is strapped to the user's chest. A set of electrodes is built into the belt and positioned just below the bust line, where the signal is strongest. The electrode belt features a built-in or attached transmitter, which sends the data to the readout unit upon detection. This eliminates the delay present in hand monitors. They are the most preferred type of monitor because of their reliability and accuracy compared to other systems. They are also more convenient, as they do not depend on physical movements and can be used with all forms of exercise. However, they are prone to interference from nearby transmitting devices such as televisions and computers.
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