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NATURE GAS SENSORS

SCM131

Characteristics

High sensitive and good selectivity to fume and alcohol.

Long life and stability

Application

Gas leakage detecting in family and industry

Suitable for detecting of methane equipments isobutane propane.

Structure of components.

Item	Descripcion	Material
1	gas sensing layer	SnO2
2	measurement electrode	Au
3	measurement electrode ignited line	Pt
4	heater	Ni-Cr alloy
5	tubular ceramic basic body	Al2 O3
6	anti-explosion network	100 dual layer stainless steel
7	clamp ring	Ni plated
8	basic seat	Bakelite
9	tube foot	Ni plated

SCM131 have 6 pins, 4 of them are used to detect signals, and other 2 are used for providing heating current.

General Specifications.

Work parameters

Symbol	Description	Operating Value	Remarks
VC	Input Voltage	5 V	AC or DC
V	Heating Voltage	5 V	AC or DC
RL	Load resistance	Adjustable	Ps < 25 mW
RH	Heater resistance	33 Ohms +/- 5%	at 21 °C
P	Power Consumption	Less than 800 Mw.

Environmental operating and storage condition

Symbol	Description	Operating Value	Remarks
Tao	Operation temperature	20 °C to 50 °C
Tas	Storage Temperature	20 °C to 70 °C
RH	Relative humidity	Less than 95% Rh
O2	Oxygen concentration	21% (at standard conditions)	minimum value is above 2%

Sensibility characteristics

Symbol	Description	Parameter	Comment	Comment
R_s	Sensor resistance	100 K 500 K (1000 ppm Alcohol)		Detection range: 50 – 1000 ppm 1000 – 20000 ppm of Isobutane
α (5000/1000) Isobutene	Concentration slope rate	≤ 0.6
Standard detecting conditions	Temp. 20 °C ± 2 °C, Vc. 5V ± 0.1 Humidity 65% ± 5% Vh. 5V ± 0.1
Pre heat time	More than 24 hours

Rs/RL= (Vc-VRL)/VRL

Characteristics

Project	Condition	Property
Vibration	frequency 100cpm	should be conformed to given sensitivity characteristic
	vertical vibrating amplitude
	time 1 hour
Punch	acceleration 100G
Punch	times 5

Handling characteristics

Variable	Conditions
Vibration	100 cpm of vertical vibration amplitude
Shock	100G

Sensibility characteristic curves for the SCM131

Relationship between VRL and the gas concentration.

The curves were characterized at the following conditions::

Temperature, 20 °C, Humidity, 65%, Oxygen concentration, 21%, RL= 100 KOhms.

Relationship Relationship between surface resistance at different environment humidity. R0 is the surface resistance at 20 °C and 0% of relative humidity and 5000 ppm of Methane.

Rs is the resistance value at different temperature and humidity.

Sensitivity adjustment.

The resistance value of the HS-131 changes with different gases and their concentrations. So, when using the sensor, it is necessary a sensitivity adjustment.

We suggest using 3000-10000ppm of methane or 300- 1000 ppm of Isobutane as standard concentration to run the adjustment procedure.

Adjustment steps:

1. Input gas to application circuits.

2. After storage please pre-heating sensor over 24 hours in order to guarantee sensor can reach stability completely.

3. In the detecting gas concentration, adjust load resistance RL until suitable output signal coming out.

4. Due to the environment conditions will affect the sensor sensitivity, please check the figure 4 to modify the sensitivity control.

Application circuit.

The circuit shown below has the temperature compensation function.

MiniSuperPLC

Starter Kit

8 inputs, 4 outputs, HMI Interface, cable & software

$98

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SCM International, Inc.

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USA

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