1. The Z19C carbon dioxide gas sensor (hereinafter referred to as the "sensor") is a general - purpose smart small - sized sensor. It uses the non - dispersive infrared (NDIR) principle to detect the presence of carbon dioxide (CO₂) in the air. 2. It has a built - in temperature compensation function, and is equipped with both serial output and PWM output, which is convenient to use. This sensor is a high - performance sensor made by closely combining the mature infrared absorption gas detection technology with precise optical path design and circuit design. 3. Detected gas: Carbon dioxide 4. Supply voltage: DC (5.0 ± 0.1) V 5. Average current: Less than 40mA (@5V power supply) 6. Current: 125 to (the original information here is incomplete) (@5V power supply) 7. Interface level: 3.3V (compatible with 5V) 8. Measurement range: 400 - 5000PPM 9. Warm - up time: 1 minute 10. Response time: T90 is less than 120 seconds 11. Operating temperature: - 10 - 50°C 12. Operating humidity: 0 - 95%RH (no condensation) 13. Pin definitions: - Vin: Power supply + (input) - GND: Power supply - (ground) - PWM: PWM - Hd: HD (calibration, low - level for more than 7 seconds is valid) - Rx: UART (RXD) TTL level data input - Tx: UART (TXD) TTL level data output 14. Type: Gas sensor 15. Model: Z19C 16. Color: Golden 17. Material: Plastic 18. Dimensions: 33 x 20mm 19. Package contents: 1 Z19C infrared CO₂ sensor module with cable 20. Only the above - mentioned package contents are included, and other items are not included. 21. Note: Light and different displays may cause the color of the item in the picture to be slightly different from the actual one. The measurement error is allowed to be ±1 - 3cm.