Heart Rate and Breathing Rate

The Zephyr BioHarness 3 is a physiological monitoring module attached to a chest strap Fig. 1, recording heart activity, breathing rate and torso acceleration

The areas marked with “HR Sensor locations” in the picture are conductive and have to be in contact with the skin; for best results it is recommended to have them moisturised before use. The breathing rate is obtained by a pressure sensor in the strap measuring the expansion of the rib cage. The user manual mentions that the breathing rates are accurate only during sedentary periods.

The main physiological parameters measured by the Zephyr BioHarness 3 as well as their properties are listed in the table below.

Measure Reporting Frequency [Hz] Range Units
ECG Amplitude
1000 (in developer mode) 0.25 – 15 mV
Heart Rate 1 0-240 Beats/minute
Breathing Rate 1 0-120 Breaths/minute
Heart Rate R-R
Per R detection 250-1500 ms (equivalent to 40-240 beats/minute)

The accuracy of the heart rate and breathing rate are provided based on the activity levels in the guidelines of the United States Army Research Institute of Environmental Medicine in the table below.

Activity Level Heart rate accuracy (beats/minute) Breathing rate accuracy (breaths/minute)
Low activity (static) 2 3
Moderate activity (walk/jog) 3 3
High activity (run) 3 5
Talking (breathing rate in
range 6-25 bpm)