1. Description

  The gas-sensitive material used in the MQ-D3B gas sensor is a semiconductor material with low conductivity in clean air. When alcohol vapor exists in the sensor's environment, the sensor's conductivity increases with the increase in the alcohol gas concentration in the air. A simple circuit can be used to convert the change in conductivity into an output signal corresponding to the gas concentration.

2. Technical specifications

3.Basic Test circuit

4.Sensor Characteristics

5.Notes:

1 Situations that must be avoided

1.1 Exposure to volatile silicon compound vapor

The sensor should avoid exposure to silicone adhesives, hair spray, silicone rubber, putty or other places where volatile silicon compounds exist. If the surface of the sensor is adsorbed with silicon compound vapor, the sensitive material of the sensor will be wrapped by silicon dioxide formed by the decomposition of the silicon compound,

suppressing the sensitivity of the sensor and making it irreversible.

1.2 Highly corrosive environment

Sensors exposed to high concentrations of corrosive gases (such as H2S, SOX, Cl2, HCl, etc.) will not only cause corrosion or damage to the heating material and sensor leads, but also cause irreversible deterioration of the performance of sensitive materials.

1.3 Alkali, alkali metal salts, halogen pollution

Sensors contaminated by alkali metals, especially salt water spray, or exposed to halogens such as Freon will also cause performance deterioration.

1.4 Contact with water

Splashing or immersion in water will cause the sensor's sensitivity to deteriorate.

1.5 Ice

Water freezing on the surface of the sensor's sensitive material will cause the sensitive layer to break and lose its sensitivity.

1.6 Excessive voltage applied

If the voltage applied to the sensor or heater is higher than the specified value, even if the sensor is not physically damaged or destroyed, it will cause damage to the lead and/or heater, and cause the sensor's sensitivity to deteriorate.

1.7 Wrong voltage applied to the sensor pins

Add 0.9 V±0.1 V DC heating voltage between sensor pins 1 and 3. Too high a voltage will damage the sensor or even burn out the electrode; add 3.0 V±0.1 V DC test voltage between pins 2 and 1 or 3.

2 Situations to avoid as much as possible

2.1 Condensation

Under indoor conditions, slight condensation will have a slight effect on sensor performance. However, if water condenses on the surface of the sensitive layer and remains for a period of time, the sensor characteristics will deteriorate.

2.2 In high concentration gas

Whether the sensor is powered or not, long-term placement in high concentration gas will affect the sensor characteristics. If the sensor is sprayed directly with lighter gas, it will cause great damage to the sensor.

2.3 Long-term storage

When the sensor is stored for a long time without power, its resistance will have a reversible drift, which is related to the storage environment. The sensor should be stored in a sealed bag that does not contain volatile silicon compounds. After long-term storage, the sensor needs to be powered for a longer time before use to stabilize it. The storage time and corresponding aging time are recommended as shown in the figure below.

2.4 Long-term exposure to extreme environments

Regardless of whether the sensor is powered or not, long-term exposure to extreme conditions such as high humidity, high temperature or high pollution will seriously affect the performance of the sensor.

2.5 Vibration

Frequent and excessive vibration can cause the internal leads of the sensor to resonate and break. Such vibrations can be generated by using pneumatic screwdrivers/ultrasonic welders during transportation and on the assembly line.

2.6 Shock

If the sensor is subjected to strong impact or falls, its lead wire will break.

2.7 Usage conditions:

2.7.1 Manual soldering is the most ideal soldering method for the sensor. The recommended soldering conditions are as follows:

Flux: Rosin flux with the least chlorine

Constant temperature soldering iron

Temperature: 250℃

Time: no more than 3 seconds

2.7.2 The following conditions should be met when using wave soldering:

Flux: Rosin flux with the least chlorine

Speed: (1-2) m/min

Preheating temperature: (100±20)℃

Soldering temperature: (250±10)℃

1 pass through the wave soldering machine

Violation of the above usage conditions will degrade the sensor characteristics.