Monitoring gas quality and concentration across a large, spread-out site is a persistent challenge for landfill operators, waste management facilities, and any organisation with hazardous or process gases to track. A single point sensor simply cannot tell you what’s happening at dozens of wellheads or throughout a sprawling building complex. This is precisely the problem that Distributed Monitoring Systems (DMS) are designed to solve.
What Is a Distributed Monitoring System?
A Distributed Monitoring System – such as the MultiLink Distributed Monitoring System (ML-DMS) – is a suite, or network of suites, of gas analysis equipment that feeds continuous readings into a computer-controlled management platform. Rather than relying on isolated, standalone sensors, the system draws samples from multiple locations across a site, analyses them centrally, and logs the results at pre-specified intervals.
Beyond simple monitoring, the ML-DMS can also close the loop on control: it can output adjustment signals to field devices such as motorised valves and heaters to maintain desired conditions automatically. For example, if a landfill operator needs to maintain a constant methane level or suction pressure at a specific wellhead, the system can instruct a motorised valve controller to open or close as needed – without manual intervention.
A single ML-DMS installation can manage up to 64 sample points, using two 760mm x 760mm enclosures, where sample points are within 150 metres of the panel and only three sweeps per day are required.
How the System Works
Gas samples are collected through 6 mm nylon tubing from distances of up to 500 metres from the analysis suite (larger bore tubing can extend this range further). Because samples are drawn sequentially, adequate time must be allowed for a representative reading to be pulled from each location, analysed, and logged – this “sweep time” is one of the key factors limiting how many sample points a single system can practically serve.
Once drawn in, each gas sample passes through a mechanical switching mechanism (to prevent cross-contamination between sample points) and a filtration stage to remove particulates. In-line analysers then determine the concentration of the target gases, typically including:
- Methane (CH₄) – infrared analysis
- Carbon Dioxide (CO₂) – infrared analysis
- Oxygen (O₂) – electrochemical cell
- Hydrogen Sulphide (H₂S) – electrochemical cell (optional)
Additional gases such as carbon monoxide, NOx, SO₂, and unburned hydrocarbons can also be incorporated depending on the application.
Readings are converted from analogue to digital signals and forwarded to a Central Control Station, typically a dedicated PC running a Graphical User Interface (GUI). The GUI presents live gas concentrations as a percentage by volume, and can be configured with 2D or 3D graphing, alarm logging, and system reporting – all tailored to the specific project.
Key Features
- PLC-controlled data acquisition for reliable, automated data handling
- Integrated moisture control at several levels within the sampling network to prevent condensation-related errors
- Wide gas compatibility – methane, carbon dioxide, oxygen, carbon monoxide, NOx, hydrogen sulphide, unburned hydrocarbons, and more
- Datalogging with remote data retrieval and remote control
- Internet compatibility as an optional extra
- Field-proven technology, refined by Organics since the early 1990s
Communication between field enclosures and the central control station runs over a 485 data-highway – a system specifically designed to eliminate the impact of electrical noise over long cable runs, which is essential when panels may be located hundreds of metres apart across an industrial or landfill site.
Typical Applications
Distributed Monitoring Systems are suited to any situation where multipoint gas readings are needed over an extended area, including:
- Wide area gas monitoring
- Wellhead control systems on gas collection networks
- Exhaust gas analysis
- Hazardous gas monitoring networks
- Refrigerated storage areas
- Greenhouses
- Building monitoring systems
Technical Specifications
Core Sensor Performance
| Parameter | Methane (CH₄) / CO₂ (Infrared) | Oxygen (O₂, Galvanic Cell) |
|---|---|---|
| Accuracy | ±2% FSD | ±1% |
| Repeatability | ±1% FSD | – |
| Response time (T90) | 5 seconds (excl. aspiration) | ~12 seconds |
| Operating temperature | 0-45°C | +5 to +40°C |
| Storage temperature | – | -20 to +60°C |
| Stability | Better than ±2% FSD/month | – |
| Power consumption | 6 W | – |
| Humidity tolerance | 0-100% non-condensing | – |
| Life expectancy | – | ~900,000 %hours (~5 years at 20°C) |
| Output | 4-20 mA (0.1 mA resolution), optional 0-20 mA or voltage | – |
The oxygen sensor exhibits virtually no cross-sensitivity to CO₂, CO, H₂S, NOx, SO₂, or H₂ – and requires no warm-up time, making it robust for continuous field deployment.
System-Level Capacity
| Feature | Specification |
|---|---|
| Max sample tubing run (standard) | Up to 500 m (larger bore for greater distances) |
| Tubing diameter | 6 mm nylon |
| Enclosure rating | IP68 (outdoor-suitable) |
| Enclosure size (standard) | 760mm x 760mm |
| Max sample points per DMS | Up to 64 (two enclosures, ≤150 m from panel, 3 sweeps/day) |
| Data communications | RS-485 data-highway (noise-resistant) |
Optional Extras
Depending on site conditions and operational requirements, the ML-DMS can be specified with:
- Panel air-conditioning – recommended for locations subject to temperature extremes
- Enclosure rain hood and operator shelter – fits to the enclosure frame, overhangs by approximately 1 metre, with triangular sides to reduce the impact of driven rain
- Automatic calibration equipment – includes a mounting facility for a sample gas cylinder, automated switching to run calibration gas through sensors at pre-programmed intervals, and auto-calibration software to reset zero and span settings
Why It Matters
Manually checking gas conditions at dozens of wellheads or sample points across a site is time-consuming, inconsistent, and prone to human error. A Distributed Monitoring System replaces that manual effort with continuous, automated, centrally logged data – supporting both regulatory compliance and operational optimisation. Where gas quality directly affects downstream processes (such as landfill gas utilisation for power generation), tighter control over wellhead conditions can translate directly into better plant performance and reduced risk.
Key Takeaways
- Distributed Monitoring Systems provide centralised, automated gas analysis across wide or dispersed sites, drawing samples from as far as 500 metres away.
- Standard configurations measure methane, CO₂, and oxygen, with optional sensors for H₂S, CO, NOx, SO₂, and more.
- Beyond monitoring, the system can drive control loops – automatically adjusting valves or heaters to maintain target gas conditions.
- Data is managed via a noise-resistant RS-485 highway and presented through a customisable GUI, with remote access and optional internet connectivity.
- Optional hardware such as automatic calibration, rain hoods, and panel air-conditioning make the system adaptable to harsh field environments.
If you’re evaluating a wide-area gas monitoring or wellhead control solution for your site, our team can help assess feasibility, provide indicative costs, and support you from specification through to installation and ongoing servicing. Get in touch with our Business Development Department to discuss your specific application.