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 air.<br> 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.<br> Detection gas:carbon dioxide<br> Power supply voltage:DC (5.0±0.1) V<br> <br> Average current:Less than 40mA (@5V power supply)<br> current:125 to (@5V power supply)<br> Interface level:3.3v(compatible with 5v)<br> Measuring range:400-5000PPM optional<br> Output signal:serial UART(TL level 3.3V)<br> Warm-up time:1min<br> Response time:T90 Less than 120s<br> Working temperature:-10-50℃<br> Working humidity:0-95RH(no condensation)<br> Pin description:<br> Vin:Power +(in)<br> GND:power supply-(GND)<br> PWM:PWM<br> Hd:HD (zero calibration, low level is effective for more than 7 seconds)<br> Rx:UART (RXD) TTL level data input<br> Tx:UART (TXD) TTL level data output<br> Output method:<br> PWM output<br> Assume the measurement range is 400-2000ppm<br> CO2:Concentration output range: 400-2000ppm<br> Period:1004ms±5<br> High level output at the beginning of the cycle: 2ms (theoretical value)<br> Central period:1000ms±5<br> Low level output at the end of the period: 2ms (theoretical value)<br> Calculation formula for obtaining current CO2 concentration value by PWM: Cppm=2000X (TH-2ms)/(TH+TL-4ms)<br> Cppm: CO2 concentration value calculated by the unit of ppm<br> TH: the time when the output is high level in one output cycle<br> TL: the time when the output is low in one output cycle<br> Due to different product batches, the appearance may vary, which does not affect the use.<br> Colour:As Shown<br> Material:PC+Aluminum Alloy<