Data Sheet

components. The enveloped MQ-135 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-135
SENSITVITY ADJUSTMENT
Resistance value of MQ-135 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
100ppm NH
3
or 50ppm Alcohol concentration in air and use value of Load resistancethat( R
L
) about 20 KΩ(10KΩ
to 47 KΩ).
When accurately measuring, the proper alarm point for the gas detector should be determined after
considering the temperature and humidity influence.
0
0. 2
0. 4
0. 6
0. 8
1
1. 2
1. 4
1. 6
1. 8
-20-100 102030405060
degr ee
Rs/R
o
33%RH
85%RH
Fig.3 is shows the typical
sensitivity characteristics of
the MQ-135 for several gases.
in their: Temp: 20

Humidity: 65%

O
2
concentration 21%
RL=20kΩ
Ro: sensor resistance at 100ppm of
NH
3
in the clean air.
Rs:sensor resistance at various
concentrations of gases.
Fig.4 is shows the typical dependence of
the MQ-135 on temperature and humidity.
Ro: sensor resistance at 100ppm of NH
3
in air
at 33%RH and 20 degree.
Rs: sensor resistance at 100ppm of NH
3
at different temperatures and humidities.
Fig.4
MQ-135
0. 1
1
10
10 100 1000
pp
m
Rs/Ro
AI R
CO2
CO
¾Æ¾
«
NH4
¼×±
½
±ûÍ
ª