The Pulse Signal Chart in emWave Pro and Pro Plus provides a real-time visualization of the raw data being captured by your sensor. Understanding what these axes represent helps clarify how the software translates biological signals into the heart rhythm patterns used for coherence training.
The X-Axis: Time
The horizontal axis (X-axis) measures Time, displayed in seconds. This allows you to see the frequency and rhythm of your pulse as it occurs throughout the session.
The Y-Axis: Raw Signal Intensity
The vertical axis (Y-axis) displays non-calibrated units. Unlike a blood pressure monitor or a thermometer, these units do not represent a standard scale like “mmHg” or “degrees.” Instead:
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Raw Voltage: The Y-axis shows the raw voltage signal recorded by the Analog-to-Digital Converter (ADC).
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Measurement Process: The ear sensor uses infra-red (IR) light to detect changes in blood density in the earlobe with each heartbeat. A photo diode converts these light modulations into voltage, which the ADC then translates into the digital signal you see on the screen.
Why Calibration Isn’t Required
You may notice that the height of the pulse waves varies between sessions or users. This is normal because HeartMath science is based on Heart Rate Variability (HRV).
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The software is designed to measure the precise time elapsed between pulses (the Inter-Beat Interval), not the magnitude or “height” of the pulses themselves.
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Because the timing is the critical data point for calculating coherence, the specific voltage units on the Y-axis are secondary and do not need to be calibrated to a universal standard.
Visualizing Coherence
While the Pulse Signal Chart shows the raw heartbeats, the Accumulated Coherence and HRV Breath charts use the timing data from the X-axis to create the smooth, wave-like patterns associated with high coherence.
Pro Tip: If your pulse signal on the Y-axis appears very small or “flat,” try re-positioning the ear sensor or warming your earlobe to improve the infra-red light’s ability to detect blood density changes.