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Quality of measurement

1. Method of measurement

Your heartrate can be measured in two technical different ways. Either in an electrical way or in an optical way.

The cosinuss° One is measuring your heartrate and heartrate variability in an optical way. Using the Circummission-Method we are sending green light emitted by an LED into your ear canal. The inner tissue is absorbing a certain amount of this light. The difference between outgoing and incoming amount of light is measured by a light-sensitive photo-diode. A special algorithm is then calculating your heartrate frequenzy.

2. Technical accuracy

Your heartrate is displayed in Beats per Minute.

  • Heartrate sensor: ±1 bpm
  • Absolute middle Deviation: ±1 bpm with best fitting
  • Limit resting heartrate: approx. 40 bpm
  • Limit maximum heartrate: approx. 220 bpm

Technical Specification – PDF

3. Precondition

Optical heart rate measurement

  • The tissue, in which the measurement takes place should let light easily come through. At the same time the tissue needs to be constantly well supplied with blood.
  • The position, where the measurement takes place should not be in heavy or jerky movement. Because this might cause unregular blood fluctuations and contact loss between the ear canal and the sensor.
  • The position, where the measurement takes place should not be as near to the core body (head and torso) as possible. In this area Vital signs are most reliable.

3.1 Messung im Gehörgang

The cosinuss° One brings its sensor technology in contact with your inner ear canal, with out being invasive. That is as close to your core body as possible. The tissue surrounding the earcanal ist light permeable and well blood supplied. During your movement you instinctively keep your head steady. The movement of your head is very careful. Therefore inside the earcanal is the perfect position for an optical measurement of vital signs.

Strength of signal and quality of measurement

3.2 Sportwatches

HRM-Watches or Sportwatches are measuring in an optical way, too. But the conditions for a measurement on the wrist are more than doubtful, due to the just described reasons above. Same is to say for other positions on your body, such as your fingers, your auricle or your lobule.

5. Size of your sensor

One of the most important factors for an accurate heartrate measurement is the continuous contact between the sensor and your skin. That is why our whole technology is adapted to the soft and pleasant silikon earbud inside your ear. It is kind of nestling to your ear canal.

Depending on the size of your ear canal, the °One is available in three different sizes S, M and L. What differs is only the size of the earbud. Until today there is no established way of measuring exactly your individual size in ear. Based on our expertise in this field we developed a table of size recommendation depending on personal height and age. Notice this is just for orientation and no no guarantee.

Size chart

6. Cosinuss vs. chest strap

Der cosinuss° One im Vergleich zum Brustgurt

The method of electrical heartrate monitoring with a chesttsrap is said to be the standard for many years now.
But issues with electrodes, that always have to be wet and that permanent feeling of being cramped can be solved now. The same with abrasions and scarring due to very heavy usage. The cosinuss° One is a better alternative to that.

Here we are presenting a measurement comparision between the cosinuss° One and a cheststrap H7 from Polar. Used in different athletic situations with different influencing factors

  • Running indoor
  • Performance diagnostics
  • Cycling indoor
  • Cycling outdoor
Updated on 22. October 2018

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