The MH-Z19C carbon dioxide gas sensor (hereinafter referred to as the sensor) is a general-purpose intelligent small sensor that uses the principle of non-dispersive infrared (NDIR) to detect the presence of C02 in the . Built-in temperature compensation: simultaneously has serial output, PWM output, easy to use. The sensor is a high-performance sensor made by closely combining mature infrared absorption gas detection technology with sophisticated optical circuit design and sophisticated circuit design. Detection gas: carbon dioxide supply voltage: DC (5.0 +/- 0.1) V Average current: less than 40mA (@5V supply) current: 125 to (@5V supply) Interface level: 3. 3v (compatible with 5v) Measuring range: 400-5000PPM Warm-up time: 1min Response time: T90less than 120s Working temperature: -10-50degree Working humidity: 0-95%RH (no condensation) Pin description: Vin: +(in) GND: supply-(GND) PWM: PWM Hd: HD (zero calibration, low level is effective for more than 7 seconds) Rx: UART (RXD) TTL level data input Tx: UART (TXD) TTL level data output Type: Gas Sensor Model Number: MH-Z19C colour:Golden Material:plastic size:33 x 20mm Package Contents: 1 x MH-Z19C IR Infrared CO2 Sensor Module With cable Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.