Gas Sensor R-134a

The ME1250 gas sensor is a remote measuring unit for monitoring the concentration of refrigerant in surrounding air. Refrigerants are generally non-toxic, but can endanger people due to their oxygen-displacing properties. The sensor is used as a leak detector for personal protection and for alarms in refrigeration systems in order not to interrupt the cold chain.

The microprocessor-controlled electronics of the sensor, adapted to the specific properties of the measuring cell, enable fast and reliable signal processing. The measured gas con-centration is transmitted to a Gas Control Panel, which can manage a large number of distributed gas sensors.

Thanks to bus communication, only one cable is required, which can be continued from sensor to sensor. The ME 1250 Gas Sensor is also available with an analogue output signal of 4…20 mA. The measured gas concentration can thereby be processed by other PLC (Programmable Logic Controllers).

The optional relay module expands the ME 1250 Gas Sensor internally with 3 relays for direct switching of signal transmitters without the use of a control panel.

Advantages

• Automatic zero point calibration
• Active noise reduction on the measurement signal
• Linear measurement signal depending on the gas concentration
• High response sensitivity with short response time
• Selective and reliable measurement with a stable measurement signal and zero point
• Temperature-compensated measurement signal
• Long service life

Technical Specifications

Measurement method	Semiconductor / Chemosorption
Measuring range	0…1,000 ppm	other measuring ranges on request
Alarm thresholds	Alarm 1: 600 ppm Alarm 2: 800 ppm	recommendation
Lifespan in air	up to 3 years	according to cell manufacturer
Break-in period	24 h	according to cell manufacturer
Response time t90	30 sec
Operating voltage	10…28 VDC	nominal 24 VDC
Ambient temperature	-10…+40 °C
Humidity	20…90% rF	non-condensing
Mounting height	30 cm above floor	heavier than air
Casing	Default: Powder-coated aluminum Orange RAL 2004 80 x 125 x 59 mm 500 g	Optional: ABS plastic Light gray RAL 7035 81 x 121 x 56 mm 250 g
Cable entry	M20
EU conformity	CE mark including EMC test

Versions

Article code	12BUS-R134A-13	1250-R134A-13
Description	Gas Sensor ME 1250 Refrigerant R-134a Bus communication	Gas Sensor ME 1250 Refrigerant R-134a Analogue
Output signal	Bus communication with gas control panel	Analogue 4…20 mA Load max. 800 Ω at 24V input
Connection	4-core cable U72M 1x4x0.6 mm Shielded	3-core cable U72M 1x4x0.6 mm or CY 0.5 mm2 Shielded
Topology	Bus, tree or star topology	Star topology
Power	< 1.9 W	< 2.5 W

Signal Processing

Accessories

Article Code	Description
1250-REL	Relay module for single sensor ME 1250
1250-AIR-BOX	Ventilation duct add-on box for gas sensor ME 1250
1250-AIR-FLOW	Fitting hose connection for gas sensor ME 1250
1250-SUP	Mounting plate round pillars for gas sensor ME 1250
1250-SCHUTZ	Sun and weather protection for gas sensor ME 1250

Consumables

Article code	Description	Lifespan
CELL-HAL-832	Measuring cell for refrigerant/chloroform	up to 3 years

Gas concentration

• The measuring cell can react to larger fluctuations in humidity
• Exposure above 800 ppm requires recalibration
• High exposure can destroy the measuring cell

Cross sensitivity

Due to the measuring method, all hydrocarbon compounds are detected. If different gases are to be expected, calibration should be made to the substance for which the sensor has the lowest sensitivity.