Data Sheet

HANWEI ELECTRONICS CO ., LTD MQ –7 http://www.hwsensor.com
TEL:[phone] 67169080 FAX:[phone] Email: [e-mail]
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
Parts Materials
1 Gas sensing
layer
SnO
2
2 Electrode Au
3 Electrode line Pt
4 Heater coil Ni-Cr alloy
5 Tubular ceramic Al
2
O
3
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
Fig.3 is shows the typical
sensitivity characteristics of
the MQ-7 for several gases.
in their: Temp: 20℃、
Humidity: 65%、
O
2
concentration 21%
RL=10kΩ
Ro: sensor resistance at 100ppm
CO in the clean air.
Rs: sensor resistance at various
concentrations of gases.
Fig.1
Fig.3 sensitivity characteristics of the MQ-7
Standard circuit:
As shown in Fig 2, standard measur
ing circuit of
MQ-7 sensitive components consists of 2 parts. one
is heating circuit having time control function (the
high voltage and the low voltage work
circularly ). The second is the signal output circuit,
it can accurately respond changes of surface
resistance of the sensor.
V
H
Vc
Heating voltage 5v (High) 60s
Heating voltage 1.4v (Low) 90s
RL
VRL
Fig.2
A
A
A向
MQ-7
0.01
0.1
1
10
100
10 100 1000 10000
ppm
Rs/Ro
CO
H2
LPG
CH4
Alcohol
air