1. High-quality double-panel design with power indication and TTL signal output indication; 2. DO switch signal (TTL) output and AO analog signal output; 3. TTL output high and low levels. (Can be directly connected to a single-chip microcomputer or relay module) 4. Analog output voltage changes with concentration. 5. There is a screw hole for easy positioning;<br><br>With long service life and reliable stability Fast response recovery characteristics Electrical performance: Input voltage: DC5V Power consumption (current): 150mA DO output: TTL digital quantity 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 20S before 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. Wiring method: 1. VCC: connected to the positive pole of the power supply (5V) 2. GND: connected to the negative pole of the power supply 3. DO: TTL switch signal output 4. AO: analog signal output 5. There are fixing bolt holes for easy installation Color: As Shown Material: PCB<br><br>Package Contents: 1 x MQ138 Formaldehyde Sensor Module<br><br>Only the above package content, other products are not included. Note: Light reflection 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.