ATEX-Certified Analog I/O Controller for Gas Flow Telemetry
Challenge
The client needed a field-deployable controller that could sit directly on gas metering equipment in hazardous, explosive-atmosphere locations - reading pressure, temperature, and mechanical encoder inputs used for gas volume correction, exchanging data with an Electronic Volume Corrector (EVC) and a GSM/GPRS/LTE modem it powers and supervises, and giving a technician a way to read and configure the unit on site via a local display and keypad, all while meeting the IP66 and ATEX certification requirements of the environment it would be installed in.
Solution
We designed a multi-interface analog and digital I/O board built around an STM32 microcontroller in STM32CubeIDE, with dedicated screw-terminal channels for temperature and pressure sensing, two encoder inputs supporting Namur, SCR, and pulse output types for mechanical gas meter reading, four digital inputs and four digital outputs, and optional 4-20mA analog input and output channels. Communication runs over an isolated RS232/RS485 interface, an onboard GSM/GPRS/LTE modem, and an optical UART interface read through an external optical head - a standard on-site meter-reading method in the gas industry - alongside dedicated supply connectors for the EVC and modem the board powers and supervises. A 2.4-inch 240x120 display with keypad input gives a field technician direct, on-site access to readings and configuration without needing a laptop or external tool. The board and its enclosure were engineered in Altium Designer and SolidWorks to meet IP66 ingress protection and ATEX certification for installation in hazardous, explosive-atmosphere locations.
Results
The finished controller gives the client a single field-installable unit that bridges mechanical gas-metering equipment - pressure, temperature, and encoder-based volume readings - with both local (RS232/RS485/optical) and remote (cellular) communication paths, while meeting the IP66 and ATEX requirements needed to install it directly at a hazardous metering site. The onboard display and keypad let field technicians commission and check the unit without extra tools, and the isolated RS485/RS232 interfaces alongside the GSM/GPRS/LTE modem keep it compatible with both existing wired infrastructure and sites with no wired connectivity at all.
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