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LCTR 903

Lowcost gas transmitter
LCTR 903

Application

The gas transmitter ADOS LCTR 903 is suitable for the detection of combustible gases, for example hydrogen, methane (natural gas) or propane / butane (LPG) in air in the LEL region. Two transmitter versions with different output signals are available:
- 3-wire 4–20 mA
- 4-wire LON® (LCTR 404)

Three measuring principles are available:
- VQ
- TGS
- IR

Fields of Application

  • Gas fired boiler systems
  • Gas distribution station
  • Gas transfer station
  • Battery-charging station

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.

1 = Circuit voltage
2 = Heating voltage
3 = Load resistor

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 conduc tivity of the test gas.

1 = Catalyzer pellistor
2 = Electric connections
3 = Inert pellistor
4 = Diffusion filter

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.

1 = Infrared-radiation source
2 = Test gas
3 = Diffusion filter
4 = nfrared-detector
5 = Measurement chamber

Technical data – for the 3 sensors

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: +4 °F to +113 °F +4 °F to +113 °F +4 °F to +113 °F
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 15 V - 30 V 15 V - 30 V 15 V - 30 V
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 IP 54 IP 54 IP 54
Dimensions
(height x diameter)		 3.15 x 3.15 inch 3.15 x 3.15 inch 3.15 x 3.15 inch
Weight 1.1 lbs 1.1 lbs 1.1 lbs