Fixed gas detector LCTR 903 - Ados

The Ados LCTR 903 gas detector is suitable for the detection of toxic, explosive and flammable gases present in the air. With three measurement principles: VQ (semiconductor), TGS (catalytic) and IR (infrared) and two communication configurations: 4 ... 20 mA, 3 wires or 4 LON® wires, the LCTR 903 is the right choice when it prevails the commitment of the binomial quality/price.

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The VQ sensor

The head of the VQ sensor functions on the principle of heat reaction. When combustible or reducing gases or vapours come in contact with the measuring element, they are subjected to catalytic combustion, which causes a rise in temperature. This rise causes a change in the resistance of the measuring element which is used as a measure of the component of gas being tested. The inert element is for compensating the temperature and conductivity of the test gas.

The TGS sensor

The TGS sensor contains a semiconductor sensor,
which is constructed on SnO₂ -sintered N-substrate.
When combustible or reducing gases are absorbed by the surface of the sensor, the concentration of the test gas is determined by the change in conductivity.

The IR sensor

The test gas flows through a measurement chamber that incorporates an IR radiating source and a two-channel infrared detector. The intensity of the infrared radiation is reduced as it passes through the gas molecules. The concentration of the gas can then be calculated by the magnitude of the reduction in intensity. Since only absorption of the wavelength (A) specific to the gas under test in relation to the wavelength (B) not absorbed by a test gas is considered, interference due to dust, ageing etc., is almost fully compensated.

Type	TGS	VQ	IR
Measurement method:	Semiconductor	Heat reduction	Infrared
Measurement range:	ppm ranges to 100 % LEL	ppm ranges to 100 % LEL	0–100 % LEL CH₄, C₃H₈, C₂H₂ 0–100 Vol % CH₄ 0–1, 2, 3, 4, 5 Vol % CO₂
Percentage error of f.s.d.:	± 5 %	± 5 %	± 3 %
Linearity:	< 15 % of f.s.d.	< 3 % of f.s.d.	< 3 % of f.s.d.
Temperature range:	-20 °C to +45 °C	-20 °C to +45 °C	-20 °C to +45 °C
Temperature effect:	5 %	2 %	8 %
Response time (t₉₀):	approx. 20 sec.	approx. 20 sec.	< 30 sec.
Pressure effect:	1 %	1 %	1 %
Mounting position:	optional	optional	optional
Application:	Poisonous, combustible and explosive gases in the LEL region	Poisonous, combustible and explosive gases in the LEL region	Poisonous, combustible and explosive gases in the LEL region
Expected operation time for sensor:	> 2 years	> 2 years	approx. 5 years
Supply voltage:	15V - 30V	15V - 30V	15V - 30V
Interface:	4–20 mA three-wire or LON^® fourwire techniques (LCTR 404), galvanically isolated, data transmission 78 kbps	4–20 mA three-wire or LON^® fourwire techniques (LCTR 404), galvanically isolated, data transmission 78 kbps	4–20 mA three-wire or LON^® fourwire techniques (LCTR 404), galvanically isolated, data transmission 78 kbps
Protection class:	IP54	IP54	IP54
Dimensions (height x diameter):	80 x 80 mm	80 x 80 mm	80 x 80 mm
Weight:	500g	500g	500g