MQ303A Alcohol Sensor
Character
* High sensitivity
* Fast response and resume
* Long life and low cost
* Mini Size
Application
MQ303A is semiconductor sensor is for Alcohol detection,
It has good sensitivity and fast response to alcohol,
suitable for portable alcohol detector.
Configuration
Technical Data
Model No.
Sensor Type
Standard Encapsulation
Detection Gas
Concentration
Heater Voltage
Loop Voltage
Standard
Circuit
Conditions
Load
Resistance
Heater
Resistance
Heater Current
Heater Power
Sensor
Consumption
Sensing
Character
Resistance
Sensitivity
Slope
R
H
I
H
P
H
P
S
R
s
S
α
V
H
V
c
R
L
MQ303A
Semiconductor
Metal
Alcohol
20-1000ppm Alcohol
0.9V ± 0.1V
AC or DC
≤6V
DC
Adjustable
4.5Ω
±
0.5
Ω（Room
Tem.）
120±20mA
≤
140 mW
≤10
mW
4KΩ-400KΩ(in air)
Rs(in air)/Rs(125ppm
Alcohol)≥3
0.50
±
0.15(R
300ppm
/R
100ppm
Alcohol)
20℃±2℃；65%±5%RH
Vc:3.0 V±0.1 V DC ；
V
H
: 0.9 V±0.1 V DC
Over 48 hours
Tem. Humidity
Condition
Standard test circuit
Preheat time
Sensing element of the semiconductor sensor is a
micro-ball, heater and metal electrode are inside,
and the sensing element is installed in
anti-explosion double 100 mesh metal case (see
the above)
Sensitivity Characteristics
Influence of Temperature/Humidity
Fig.2 is the test circuit. You could get resistance
change from voltage change on fixed or adjustable
load resistance. Normally, it will take several
minutes preheating for sensor enter into stable
working after electrified; oryou could give
2.2±0.2V high voltage for 5-10secs before test,
which make sensor easily stable.
Fig 3 is sensitivy of MQ303A, it reflects
relations between resistance and gas
concentration, resistance of the sensor
reduce when gas concentration increases
Notification
1 Following conditions must be prohibited
1.1 Exposed to organic silicon steam
Organic silicon steam cause sensors invalid, sensors must be avoid exposing to silicon bond,
fixature, silicon latex, putty or plastic contain silicon environment
1.2 High Corrosive gas
If the sensors exposed to high concentration corrosive gas (such as H
2
Sz, SO
X
，Cl
2
，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 fluorin.
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’surface, otherwise sensor would lose sensitivity.
1.6 Applied voltage higher
Applied voltage on sensor should not be higher than stipulated value, otherwise it cause down-line or
heater damaged, and bring on sensors’ sensitivity characteristic changed badly.
1.7 Voltage on wrong pins
For 6 pins sensor, if apply voltage on 1、3 pins or 4、6 pins, it
will make lead broken, and without signal when apply on 2、4 pins
2 Following conditions must be avoided
2.1 Water Condensation
Indoor conditions, slight water condensation will effect sensors performance lightly. However, if water
condensation on sensors surface and keep a certain period, sensor’ sensitivity will be decreased.
2.2 Used in high gas concentration
No matter the sensor is electrified or not, if long time placed in high gas concentration, if will affect
sensors characteristic.
2.3 Long time storage
The sensors resistance produce reversible drift if it’s stored for long time without electrify, this drift is
related with storage conditions. Sensors should be stored in airproof without silicon gel bag with clean air.
For the sensors with long time storage but no electrify, they need long aging time for stbility before using.
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 effect the sensors performance badly.
2.5 Vibration
Continual vibration will result in sensors down-lead response then repture. 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
For sensor, handmade welding is optimal way. If use wave crest welding should meet the following
conditions:
2.7.1 Soldering flux: Rosin soldering flux contains least chlorine
2.7.2 Speed: 1-2 Meter/ Minute
2.7.3 Warm-up temperature：100±20℃
2.7.4 Welding temperature：250±10℃
2.7.5 1 time pass wave crest welding machine
If disobey the above using terms, sensors sensitivity will be reduced.
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