Employs a high-quality dual-panel design, featuring a power indicator and TTL signal output indicator. With DO (TTL) switching signal output and AO analog signal output TTL high and low level output. (Can be directly connected to the microcontroller or relay module) The analog output voltage changes with concentration. Fast response recovery feature. Has a long lifespan and reliable stability. Electrical performance: Input voltage: DC5V Power consumption (current): 150mA DO output: TTL digital quantities 0 and 1 (0.1 and 5V) AO output: analog level signal Special reminder: After the sensor is powered on, it needs to be preheated for about 20 seconds, and the measured data is stable. It is normal for the sensor to heat up, because there is a heating wire inside, if it is hot it is not normal. Connection: 1. VCC: connect to the positive pole of the power supply (5V) 2. GND: connect to the negative pole of the power supply 3. DO: TTL switching signal output 4, AO: Analog signal output Color: green Material: Metal Package Contents: 1 x MQ139 Freon Sensor Module Only the above package content, other products are not included. Note: Light shooting and different displays may cause the color of the item in the picture to be slightly different from the real item. The allowable measurement error is +/- 1-3 cm.