In physical examination centers, hospitals, and health management institutions, the Shanghe Smart Height and Weight Meter, thanks to its high precision and intelligent features, has become a core device for collecting health data. Users often raise a key question: Does the height measured by these devices include hair length? This article will analyze the technical principles, device design, and practical application scenarios.
Ⅰ. Technical Principle: Accuracy of Ultrasonic Distance Measurement
The Shanghe Smart Height and Weight Meter utilizes **ultrasonic distance measurement technology**. Its core principle is that an ultrasonic sensor at the top of the device emits high-frequency sound waves. The sound waves hit the top of the head and reflect back to the sensor. The system calculates the round-trip time of the sound waves to determine the distance. This is then combined with the fixed height from the bottom of the device to the ground to calculate the person's net height.
Key Points:
1. Sound Wave Reflection Point: Ultrasound waves typically reflect from the skin on top of the head or from the hair close to the scalp, not from loose ends.
2. Error Control: The device's built-in intelligent algorithm and environmental compensation function automatically correct for the effects of external factors such as temperature and humidity on sound velocity, ensuring measurement errors within ±0.5 cm.
3. Hair Effect: If hair is fluffy (such as curly hair or curly hair) or if you wear thick headwear, the sound waves may be reflected prematurely, resulting in an inaccurate measurement of 1-3 mm. However, this error is far below the device's nominal accuracy.

II. Device Design: Optimizing Hair Interference
During the development phase, the Shanghe series of devices fully considered the potential impact of hair on measurement and implemented the following design features to minimize errors:
1. Sensor Positioning: The ultrasonic probe is fixed to the top of the device**, emitting sound waves vertically downward to avoid erroneous reflection points due to angular deviation.
2. Voice Guidance: During measurement, the device prompts the user to "straighten your head and flatten your hair" through voice and animation to ensure that the sound waves reach the scalp directly.
User Suggestions: How to Obtain the Most Accurate Data
To ensure that the measurement results reflect your true height, users can follow the following steps:
1. Preparation:
- Remove shoes and stand in front of the device with your feet shoulder-width apart.
- Comb your hair close to your scalp and avoid using hairspray or wigs.
- Remove any head ornaments, such as hats and headscarves.
2. Posture During Measurement:
- Keep your head upright and your eyes looking straight ahead. - Take a deep breath and stand naturally, avoiding standing on tiptoe or bending over.
3. Data Verification:
- If you have any doubts about the results, you may request 2-3 remeasurements and take the average. The Shanghe Smart Height and Weight Meter utilizes ultrasonic technology, an environmental compensation algorithm, and a user-friendly design to achieve highly accurate height measurement. Although hair thickness may cause minor errors, standardized operation and the device's built-in error correction mechanisms keep these effects within clinically acceptable limits. For the average user, there's no need to worry too much about hair interference. However, for research scenarios requiring extreme precision, manual remeasurement is recommended to ensure data integrity.