GF-201-CH4 Combustible Gas Sensor

Overview

The GF-201-CH4 is a fixed-point combustible gas detector for continuous methane monitoring in biogas, livestock, and industrial environments. It reads in %LEL, percent of the lower explosive limit: 100 %LEL is the concentration at which methane becomes ignitable. A sensing cell with automatic temperature compensation holds readings stable over long deployments, while a flameproof aluminium alloy enclosure (Ex d IIC T6) suits hazardous areas where gas may be present.

The sensor shows live concentration and alarm status on its LCD and drives three independent output paths at once: a 4-20 mA analog loop, an RS485 Modbus-RTU bus, and two normally-open alarm relays. That lets a single unit report to an Omni Genesis controller while its relays directly trigger a fan, solenoid, or local horn.

Why Monitor Combustible Gas

Manure digesters and biogas plants on dairy farms produce methane by design, so any leak around digester covers, valves, and gas piping must alarm early. Slurry pits and enclosed waste handling areas accumulate methane even without a digester on site. Continuous fixed-point detection with a two-stage alarm lets the relays drive ventilation or a gas shutoff before concentrations approach ignitable levels.

Key Features

• Combustible gas range: 0-100 %LEL with 0.1 %LEL resolution; 0-10 %VOL and 0-50 %VOL ranges available on request
• Fast response: ≤25 s (T90), with automatic temperature compensation
• Two-stage alarm: independent low and high relays, freely configurable set points
• Three outputs in parallel: 4-20 mA, RS485 Modbus-RTU, and two dry-contact relays
• Hazardous-area rated: flameproof Ex d IIC T6 aluminium enclosure, IP65
• Wide supply: 12-30 VDC, ≤2 W
• Field serviceable: LCD menu for calibration, alarm set points, and bus address

How It Works

The sensing cell with automatic temperature compensation produces a signal proportional to the combustible gas concentration at the sensor inlet. On-board electronics linearise that signal, display it in %LEL, and publish it on the analog and digital outputs. When concentration crosses a configured set point, the matching relay changes state to drive an alarm or interlock.

Installation

Because methane is lighter than air, mount the sensor high, roughly 0.3-0.6 m below the ceiling, above likely release points such as digester covers, valves, and gas piping. Keep the sensor inlet clear of splashing water, oil, and dust, and leave service access around the housing. Calibrate with certified gas at commissioning and at least every six months thereafter.

One Detector, Replaceable Sensing Cell

The GF-201 family shares one platform: the same flameproof housing, display, relays, and outputs, with a replaceable sensing cell that sets the target gas. The family: H2S, NH3, CO2, O2, and CH4.

Additional sensing cells are available for the same platform by quote:

Gas	Formula	Selectable ranges
Carbon monoxide	CO	0-500 to 0-10000 ppm
Ozone	O3	0-10 to 0-1000 ppm
Chlorine dioxide	ClO2	0-20 to 0-1000 ppm
Chlorine	Cl2	0-10 to 0-200 ppm
Sulfur dioxide	SO2	0-100 to 0-1000 ppm
Nitrogen dioxide	NO2	0-100 to 0-1000 ppm
Formaldehyde	CH2O	0-5 to 0-200 ppm
Ethylene	C2H4	0-50 to 0-1000 ppm

Contact us with your target gas and range for a tailored quote.

Connectivity and Integration

The RS485 Modbus-RTU output (9600 bps, 8-N-1) connects directly to the Omni Genesis and Genesis Lite controllers and to any PLC or DCS that speaks Modbus. The parallel 4-20 mA loop covers legacy analog inputs, and the two relay contacts provide a wiring-free local trip for a ventilation fan or gas shutoff interlock. This is the same modular approach as the rest of the Agrinovo range: one controller, any mix of sensors.