The Gill AF120 is a standalone air/fuel ratio controller designed to maintain precise Lambda control on stationary gaseous-fuel engines burning natural gas, biogas, landfill gas, or propane. Unlike open-loop mixer-based systems that drift with fuel composition and ambient conditions, the AF120 continuously reads exhaust oxygen content via a heated wideband UEGO sensor and adjusts the fuel valve in real time using a Proportional + Integral control algorithm.

How does AF120 control fuel flow?

The controller outputs to either a stepper motor-based bypass fuel valve (200+ discrete steps for fine resolution) or a 4–20 mA signal driving a pneumatic control valve — giving flexibility for different gas train configurations. A programmable load map correlates throttle position or manifold absolute pressure (MAP) sensor input to target Lambda, allowing rich-burn stoichiometric operation with a three-way catalyst or lean-burn strategies for efficiency-optimized engines. Adjustable parameters — valve start position, sensor warm-up time, and control offset — enable commissioning without a laptop, though a free Windows GUI over RS232 provides full configuration access.

What environmental conditions does AF120 tolerate?

With an operating range of -40°C to +90°C and IP67 dust-tight/water-immersion sealing, the AF120 mounts directly in the engine bay or on the gas train skid — no climate-controlled enclosure needed. CSA Class 1 Division 2 certification (Groups C and D, when installed in the companion EH12 shielded enclosure) permits deployment at wellhead gas compression sites, wastewater treatment biogas plants, and landfill gas-to-energy stations where flammable atmospheres may be present under abnormal conditions.