Integration of Gas Detectors with PLC/SCADA Systems
Linking gas detectors to PLC (Programmable Logic Controller) or SCADA (Supervisory Control and Data Acquisition) systems enables real-time monitoring, centralized alarm management, and automated safety responses in industrial environments. This integration ensures that gas concentration data is not only displayed locally but also transmitted to control rooms for immediate action. The GDE series from Shanghai Gowe Electronic Safety Equipment Co., Ltd. supports multiple output modes including 4-20mA, RS485, and relay signals, making it compatible with most PLC/SCADA architectures.
Signal Output and Compatibility
The 4-20mA analog output is widely used in industrial control systems due to its noise immunity and long-distance transmission capability. Gowe’s GDE and GDC series provide programmable current outputs with defined fault states: 0-2mA for power failure, 2-2.5mA for sensor fault, 3mA during calibration, and 4-20mA for concentration readings. This allows PLCs to interpret not only gas levels but also device health. The RS485 bus interface supports daisy-chain topology with a maximum distance of 1.5 km, enabling cost-effective wiring in large plants. Up to 256 detectors can be connected on a single bus with proper addressing.
Alarm Handling and Logic Programming
Each Gowe detector includes dual relay outputs: one for low-level alarm and one for high-level alarm. These relays are rated at 2A @ 120VAC/30VDC and can directly trigger sirens, exhaust fans, or emergency shutdown circuits. In a PLC/SCADA setup, these signals are wired to digital input modules, where ladder logic or function block programming can be used to initiate actions such as valve closure, ventilation activation, or SMS alerts via IoT gateways. The GDC series also supports Modbus RTU over RS485, enabling direct integration with SCADA HMI screens without additional protocol converters.
Proof-Testing Procedures and System Validation
Regular proof-testing is required by safety standards such as ISO 13849 and SIL (Safety Integrity Level) requirements. The proof-testing process involves simulating gas exposure using certified test gas and verifying that alarms, relays, and SCADA notifications activate within specified time limits. Gowe detectors feature a pre-calibrated smart plug-in sensor module, which allows for quick replacement and reduces downtime during testing. The GDE series includes automatic temperature and zero compensation, minimizing false readings during test cycles.
Automated Test Sequences via SCADA
Advanced SCADA systems can be programmed to initiate automated proof-testing sequences. Using a test gas dispenser connected to a solenoid valve, the SCADA system opens the valve for a fixed duration (e.g., 30 seconds) to expose the detector. The system then monitors the 4-20mA signal and relay status to confirm response time and alarm activation. Test results, including pass/fail status and response time (T90), are logged into a database for compliance reporting. Gowe’s GM810/GM820 gas alarm controllers support such automation with their modular design and Modbus communication, acting as a bridge between field devices and central systems.
Sensor Drift and Maintenance Alerts
Over time, gas sensors exhibit zero and sensitivity drift. The GDE and GDA series implement automatic zero calibration and drift compensation algorithms, reducing the need for manual recalibration. When drift exceeds 2% over six months (as per technical specifications), the detector sends a fault signal (2.5mA) to the PLC, prompting maintenance teams to perform a full calibration or sensor replacement. This proactive approach enhances system reliability and reduces unplanned downtime.
Data Logging and Cloud Integration
Gowe’s IoT-enabled gas detectors support 4G and Wi-Fi modules, allowing data to be uploaded to the company’s proprietary cloud platform. This platform provides real-time dashboards, historical trend analysis, and remote alarm notifications via mobile apps. When integrated with SCADA, the cloud acts as a secondary data repository and enables off-site monitoring. The GM820 controller includes built-in data logging, storing up to 10,000 events locally, which can be exported to SCADA via FTP or OPC UA.
Redundancy and Fault Tolerance
For critical applications, dual gas detectors can be installed in the same area and connected to separate PLC input channels. The GDA series supports both explosion-proof and dust-explosion-proof certifications, ensuring safe operation in hazardous zones. If one detector fails, the other continues monitoring, and the SCADA system flags the fault for maintenance. The GM810/GM820 controllers use multiple circuit protection designs, eliminating the need for external surge suppressors and enhancing system uptime.
Effective linkage between gas detectors and PLC/SCADA systems requires careful planning of signal types, communication protocols, alarm logic, and maintenance routines. Gowe’s product portfolio—spanning GDE, GDC, GDA detectors and GM8 series controllers—provides a complete solution with high compatibility, robust diagnostics, and support for modern industrial automation standards.