RT-H001 Heart Rate Module Measurement

1. Heart rate measurement principle

1. What is a heart rate module?

The heart rate module is designed to monitor pulse from body locations such as the wrist, finger, forehead, earlobe, or chest. The module uses a reflective photoplethysmography optical sensor to detect blood flow through the skin and processes the signal with a dedicated algorithm to obtain the current heart rate.

Heart rate varies with activity. When the subject is stationary, typical measurement error is less than 3 BPM. During motion the error increases; typical error is below 10 BPM (under normal exercise conditions usually below 5 BPM).

2. How to calculate target exercise heart rate

Calculate the exercise heart rate range as follows. Subtract the subject's age from 220 to get the maximum heart rate, then compute the lower and upper exercise heart rate using:

220 - age = maximum heart rate (MHR);
MHR * 0.6 = lower exercise heart rate;
MHR * 0.9 = upper exercise heart rate.

3. Data analysis

The range between the lower and upper exercise heart rates defines the personal exercise heart rate zone. If measured heart rate is inside this range, the subject's exercise condition is appropriate; if outside the range, the subject should adjust training. Athletes often have longer endurance and greater capacity because regular training increases cardiac output and circulation, improving oxygen uptake and aerobic energy production. For typical adults, pulse recovery time after exercise is greater than 10 minutes, commonly 12 to 15 minutes.

2. Solution overview

The RT-H001 heart rate module measures pulse by detecting blood flow at body sites such as the wrist, back of the hand, forehead, or ear. It uses photons at specific wavelengths in a reflective optical detection mode and applies signal-processing algorithms to derive the instantaneous heart rate. Measurement error is typically below 3 BPM at rest and below 10 BPM during motion (usually under 5 BPM during normal exercise).

3. Main components

1. Heart rate sensor LST1303
2. Precision operational amplifier LST221
3. Low-power MCU

4. Schematic and photos

The module is circular with a diameter of 12 mm, mounting hole diameter 1.1 mm, and thickness 1.5 mm (excluding the optical sensor). The PCB thickness is 0.4 mm and component height is 1.1 mm.

5. Key characteristics

Operating voltage 3.3 V, operating current 6.5 mA; sleep current: 1 μA.
Reflective heart rate sensor with high sensitivity and good accuracy, capable of relatively accurate monitoring during motion.
Compact module area with direct heart rate output, suitable for integration into secondary products such as wearable bands, watches, helmets, Bluetooth headsets, and smart glasses.
Mature design with stable performance, low cost, and low power, facilitating shorter product development cycles and straightforward integration.