Principle Introduction:
Winsen Electronics, research and produce air quality monitoring gas sensor for home and office air cleaners, and fresh air system.
MP135 gas sensor is for air quality. It adopts multilayer thick film manufacturing technology. The heater and metal oxide semiconductor material on the ceramic substrate of subminiature Al2O3 are fetched out by electrode down-lead, encapsulated in metal socket and cap. Conductivity of the sensor is affected by the concentration of target gas. The higher the concentration is, the higher conductivity of sensor gets. Users can adopt simple circuit to convert variation of conductivity into output signal corresponding to gas concentration.

Applications :
It is used in occasions such as household and office for harmful gas detection,automatic exhaust device,air cleaner…etc.

Technical parameters :

Tips:For more parameter information, please refer to the latest manual provided by salesman.

Model			MP135
Sensor Type			Semiconductor flat surfaced sensor
Standard Encapsulation			Metal Cap
Detection Gas			H2,Alcohol, CO
Detection range			10～500ppmH2 5～500ppm Alcohol 10～500ppm CO
Standard circuit	Loop voltage	VC	≤24V DC
	Heating voltage	VH	5.0V±0.1V AC or DC
	Load resistance	RL	Adjustable
sensor features in standard test condition	Heating resistance	RH	95Ω±10Ω(Room Tem.)
	Heating consumption	PH	≤300mW
	Surface resistance	RS	10KΩ～100KΩ(in 50ppm H2 )
	Sensitivity	S	Rs(in air)/Rs(in 50ppmH2)≥3
	Concentration slope	α	≤0.6(R100ppm/R30ppm H2)
Standard condition of test	Temperature, humidity		20℃±2℃；65%±5%RH
	Standard test circuit		VC:5.0V±0.1V； VH :5.0V±0.1V
	Warm-up time		More than 48 hours

Reference Circuit :

Instructions:The above fig is the basic test circuit of MP135.The sensor requires 2 voltage inputs: heater voltage(VH) and circuit voltage(VC). VHis used to supply standard working temperature to the sensor and it can adopt DC or AC power, while VRL is the voltage of load resistance RLwhich is in series with sensor. Vc supplies the detect voltage to load resistance RL and it should adopts DC power.

Typical temperature/humiditycharacteristics
Rs means resistance of sensor in 50ppm H2 under different tem. and humidity. Rsomeans resistance of the sensor in 50ppm H2 under20℃/55%RH.

long-term Stability of MP135
NOTE: Test is finished in standard test conditions, the abscissa is observing time and the ordinate is VRL.
Cautions
1 .Following conditions must be prohibited
1.1 Exposed to volatilizableorganic silicon steam
Sensing material will lose sensitivity and never recover if the sensor absorbs organic silicon steam. Sensors must be avoided exposing to silicon bond, fixature, silicon latex, putty or plastic contain silicon environment.
1.2 High Corrosive gas
If the sensors are exposed to high concentration corrosive gas (such as H2S, SOX, Cl2, HCl etc.), it will not only result in corrosion of sensors structure, also it cause sincere sensitivity attenuation.
1.3 Alkali, Alkali metals salt, halogen pollution
The sensors performance will be changed badly if sensors be sprayed polluted by alkali metals salt especially brine, or be exposed to halogen such as fluorine.
1.4 Touch water
Sensitivity of the sensors will be reduced when spattered or dipped in water.
1.5 Freezing
Do avoid icing on sensor’s surface, otherwise sensing materialwill be broken and lost sensitivity.
1.6 Applied higher voltage
Applied voltage on sensor should not be higher than stipulated value, even if the sensor is not physically damaged or broken, it causes down-line or heater damaged, and bring on sensors’ sensitivity characteristic changed badly.
1.7 Voltage on wrong pins
As Fig8,Pin 1&2 connects to heater circuit, Pin 3&4 connects to measuring circuit; Under the requested conditions, heating and measuring can use the same power circuit.
NOTE:the two pins near the protuberance mark is heating electrode.

2 .Following conditions should be avoided
2.1 Water Condensation
Indoor conditions, slight water condensation will influence sensors’ performance lightly. However, if water condensation on sensors surface and keep a certain period, sensors’ sensitive will be decreased.
2.2 Used in high gas concentration
No matter the sensor is electrified or not, if it is placed in high gas concentration for long time, sensors characteristic will be affected. If lighter gas sprays the sensor,it will cause extremely damage.
2.3 Long time storage
The sensors resistance will driftreversibly if it’s stored for long time without electrify, this drift is related with storage conditions. Sensors should be stored in airproof bag without volatile siliconcompound. For the sensors with long time storage but no electrify, they need long galvanical aging time for stabilitybefore using. The suggested aging time as follow:

Storage Time	Suggested aging time
Less than one month	No less than 48 hours
1 ~ 6 months	No less than 72 hours
More than six months	No less than 168 hours

2.4 Long time exposed to adverse environment
No matter the sensors electrified or not, if exposed to adverse environment for long time, such as high humidity, high temperature, or high pollution etc., it will influence the sensors’ performance badly.
2.5 Vibration
Continual vibration will result in sensors down-lead response then break. In transportation or assembling line, pneumatic screwdriver/ultrasonic welding machine can lead this vibration.
2.6 Concussion
If sensors meet strong concussion, it may lead its lead wire disconnected.
2.7 Usage Conditions
2.7.1For sensor, handmade welding is optimal way. The welding conditions as follow:
• Soldering flux: Rosin soldering flux contains least chlorine
• homothermalsolderingiron
• Temperature： 250℃
• Time：less than 3 seconds
2.7.2If users choose wave-soldering, the following conditions should be obey:
• Soldering flux: Rosin soldering flux contains least chlorine
• Speed: 1-2 Meter/ Minute
• Warm-uptemperature：100±20℃
• Welding temperature：250±10℃
• One time pass wave crest welding machine
If disobey the above using terms, sensors sensitivity will be reduced.

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