MQ-3 Datasheet by Parallax Inc.

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TEL: 86-371- 67169070 67169080 FAX: 86-371-67169090 E-mail: sales@hwsensor.com
TECHNICAL DATA
MQ-3 GAS SENSOR
FEATURES
* High sensitivity to alcohol and small sensitivity to Benzine .
* Fast response and High sensitivity
* Stable and long life
* Simple drive circuit
APPLICATION
They are suitable for alcohol checker, Breathalyser.
SPECIFICATIONS
A. Standard work condition
Symbol Parameter name Technical condition Remarks
Vc Circuit voltage 5V±0.1 AC OR DC
V
H Heating voltage 5V±0.1 ACOR DC
R
L Load resistance 200KΩ
R
H Heater resistance 33Ω±5% Room Tem
P
H Heating consumption less than 750mw
B. Environment condition
Symbol Parameter name Technical condition Remarks
Tao Using Tem -10-50
Tas Storage Tem -20-70
R
H Related humidity less than 95%Rh
O
2 Oxygen concentration 21%(standard condition)Oxygen
concentration can affect sensitivity minimum value is
over 2%
C. Sensitivity characteristic
Symbol Parameter name Technical parameter Remarks
Rs Sensing Resistance 1MΩ- 8 MΩ
(0.4mg/L alcohol )
α
(0.4/1 mg/L)
Concentration slope rate
0.6
Standard
detecting
condition
Temp: 20℃±2 Vc:5V±0.1
Humidity: 65%±5% Vh: 5V±0.1
Preheat time Over 24 hour
Detecting concentration
scope
0.05mg/L10mg/L
Alcohol
D. Structure and configuration, basic measuring circuit
Parts Materials
1
Gas sensing
layer SnO2
2
Electrode Au
3
Electrode line Pt
4
Heater coil Ni-Cr alloy
5
Tubular ceramic
Al2O3
6
Anti-explosion
network Stainless steel gauze
(SUS316 100-mesh)
7
Clamp ring Copper plating Ni
8
Resin base Bakelite
9
Tube Pin Copper plating Ni
AA
Fig. 1
Configuration A
Configuration B
Fig.2
HANWEI ELETRONICS C0.,LTD MQ-3 http://www.hwsensor.com :sales@ hwsensor.cam
HANWEI ELETRONICS CO.,LTD MQ-3 http://www.hwsensor.com
TEL: 86-371- 67169070 67169080 FAX: 86-371-67169090 E-mail: sales@hwsensor.com
Structure and configuration of MQ-3 gas sensor is shown as Fig. 1 (Configuration A or B), sensor composed by
micro AL2O3 ceramic tube, Tin Dioxide (SnO2) sensitive layer, measuring electrode and heater are fixed into a
crust made by plastic and stainless steel net. The heater provides necessary work conditions for work of
sensitive components. The enveloped MQ-3 have 6 pin ,4 of them are used to fetch signals, and other 2 are used
for providing heating current.
Electric parameter measurement circuit is shown as Fig.2
E. Sensitivity characteristic curve
Fig.2 sensitivity characteristics of the MQ-3
SENSITVITY ADJUSTMENT
Resistance value of MQ-3 is difference to various kinds and various concentration gases. So,When using
this components, sensitivity adjustment is very necessary. we recommend that you calibrate the detector for
0.4mg/L ( approximately 200ppm ) of Alcohol concentration in air and use value of Load resistancethat( RL) about
200 KΩ(100KΩ to 470 KΩ).
When accurately measuring, the proper alarm point for the gas detector should be determined after
considering the temperature and humidity influence.
Rs/Ro--Temp
0.50
0.60
0.70
0.80
0.90
1.00
1.10
1.20
1.30
1.40
1.50
1.60
1.70
-10 0 10 20 30 40 50 60
Temp
Rs/Ro
33%RH
85%RH
Fig.3 is shows the typical
sensitivity characteristics of
the MQ-3 for several gases.
in their: Temp: 20℃、
Humidity: 65%
O
2 concentration 21%
RL=200kΩ
Ro: sensor resistance at 0.4mg/L of
Alcohol in the clean air.
Rs:sensor resistance at various
concentrations of gases.
Fig.4 is shows the typical
dependence of the MQ-3 on
temperature and humidity.
Ro: sensor resistance at 0.4mg/L of
Alcohol in air at 33%RH and 20
Rs: sensor resistance at 0.4mg/L of
Alcohol at different temperatures
and humidities.
Fig.4
MQ-3
0.1
1
10
100
0.1 1 10
mg/L
Rs/Ro
Alcohol
Benzine
CH4
Hexane
LPG
CO
Air

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