Alcohol Gas Sensor
（Model：MQ-3）
Manual
Version: 1.3
Valid from: 2014-05-01
Zhengzhou Winsen Electronics Technology Co., Ltd
Statement
This manual copyright belongs to Zhengzhou Winsen Electronics Technology Co., LTD. Without the
written permission, any part of this manual shall not be copied, translated, stored in database or
retrieval system, also can’t spread through electronic, copying, record ways.
Thanks for purchasing our product. In order to let customers use it better and reduce the faults
caused by misuse, please read the manual carefully and operate it correctly in accordance with the
instructions. If users disobey the terms or remove, disassemble, change the components inside of
the sensor, we shall not be responsible for the loss.
The specific such as color, appearance, sizes &etc, please in kind prevail.
We are devoting ourselves to products development and technical innovation, so we reserve the
right to improve the products without notice. Please confirm it is the valid version before using this
manual. At the same time,
users’ comments on
optimized using way are welcome.
Please keep the manual properly, in order to get help if you have questions during the usage in the
future.
Zhengzhou Winsen Electronics Technology CO., LTD
Zhengzhou Winsen Electronics Technology Co., Ltd
www.winsensor.com
MQ-3 Semiconductor Sensor for Alcohol Gas
Profile
Sensitive material of MQ-3 gas sensor is SnO
2,
which
with lower conductivity in clean air. When the target
alcohol gas exist, the sensor’s conductivity gets
higher along with the gas concentration rising. Users
can convert the change of conductivity to correspond
output signal of gas concentration through a simple
circuit.
MQ-3 gas sensor has high sensitivity to alcohol
gas and can resistant to the interference of gasoline,
smoke and vapour. It is with low cost and suitable for
various applications of detecting alcohol at different
concentration.
Features
It has good sensitivity to alcohol in wide range, and has advantages such as long lifespan, low cost and
simple drive circuit &etc.
Main Applications
It is widely used in domestic alcohol gas alarm, industrial alcohol gas alarm and portable alcohol detector.
Technical Parameters
Model
Sens or Type
Sta nda rd Enca ps ul a ti on
Ta rget Ga s
Detecti on ra nge
Loop Vol ta ge
Sta nda rd Ci rcui t
Condi ti ons
Hea ter Vol ta ge
Loa d Res i s ta nce
Stable.1
MQ-3
Semi conductor
Pl a s ti c ca p
Al cohol ga s
25~500ppm a l cohol
V
c
V
H
R
L
R
H
P
H
S
Vs
α
≤24V DC
5.0V±0.1V AC or DC
Adjus ta bl e
29Ω±3Ω (room tem.)
≤900mW
Ro(i n a ir)/Rs (125ppm C
2
H
5
OH)≥5
2.5V~4.0V (i n 125ppm C
2
H
5
OH)
≤0.6(R
300ppm
/R
50ppm
C
2
H
5
OH)
20℃±2℃；55%±5%RH
Vc:5.0V±0.1V
V
H
:5.0V±0.1V
Over 48 hours
Hea ter Res i s ta nce
Sensor character
under standard
tes t conditions
Hea ter cons umpti on
Sens i ti vi ty
Output Vol ta ge
Concentra ti on Sl ope
Tem. Humi di ty
Sta nda rd tes t
condi ti ons
Sta nda rd tes t ci rcui t
Prehea t ti me
NOTE: Output voltage (Vs) is V
RL
in test environment.
Tel: 86-371-67169097/67169670
Fax: 86-371-60932988
Fig1.Sensor S
tructure
Unit: mm
Email:
sales@winsensor.com
Zhengzhou Winsen Electronics Technology Co., Ltd
www.winsensor.com
Basic Circuit
Fig2. MQ-3 Test Circuit
Instructions: The above fig is the basic test circuit of MQ-3.The sensor requires two voltage inputs:
heater voltage (V
H
) and circuit voltage (V
C
). V
H
is used to supply standard working temperature to
the sensor and it can adopt DC or AC power, while V
RL
is the voltage of load resistance R
L
which is in
series with sensor. Vc supplies the detect voltage to load resistance R
L
and it should adopt DC
power.
Description of Sensor Characters
C
2
H
5
OH
Air
CO
H
2
Gas Concentration(ppm)
Fig3.Typical Sensitivity Curve
The ordinate is resistance ratio of the sensor (Rs/R
0
), the
abs cissa is concentra tion of gases. Rs means resistance in
ta rget gas wi th different concentra tion, R
0
means
resistance of sensor i n clean air. All tests a re finished
under standard test conditions.
Fig4.Typical temperature/humidity characteristics
The ordina te is resista nce ra tio of the sensor (Rs/Rso). Rs
means resistance of sensor in 125ppm al cohol (C
2
H
5
OH)
under different tem. and humi dity. Rso means resistance of
the s ensor i n 125 a lcohol(C2H5OJ) under 20℃/55%RH.
Tel: 86-371-67169097/67169670
Fax: 86-371-60932988
Email:
sales@winsensor.com
Zhengzhou Winsen Electronics Technology Co., Ltd
www.winsensor.com
125ppm C
2
H
5
OH(RL=4.7k)
Gas Concentration(ppm)
Time(s)
Fig5.Sensitity Curve
Fi g5 shows the V
RL
i n al cohol with di fferent concentration.
The resistance load R
L
is 4.7 KΩ a nd the test is finished in
s ta ndard test conditions.
Fig6.Responce and Resume
Fi g5 shows the changing of V
RL
in the process of
putti ng the sensor into ta rget gas and removing i t
out.
125ppm C
2
H
5
OH(RL=4.7k)
Time(day)
Fig6.long-term Stability
Tes t i s finished in standard test conditions, the a bscissa i s observing time a nd the ordinate is V
RL
.
Cautions
1 .Following conditions must be prohibited
1.1 Exposed to organic silicon steam
Sensing material will lose sensitivity and never recover if the sensor absorbs organic silicon steam.
Sensors must avoid 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 H
2
S, 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 fluorine.
Tel: 86-371-67169097/67169670
Fax: 86-371-60932988
Email:
sales@winsensor.com
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