How Qube Technologies’ Methane Sensors Achieve Reliable Accuracy in Long-Term Deployments

Author: Ben Montgomery, Brad Roger, Alex MacGregor

Accurate and reliable industrial methane detection is necessary to reduce emissions, control business costs, and ensure regulatory compliance. Qube Technologies has developed an innovative methane continuous monitoring device using metal oxide (MOx) sensing technology. The design of Qube’s industrial internet of things (IIoT) sensors is illustrated in Figure 1.  

Figure 1 – Qube's IIoT continuous monitoring devices.

Qube’s sensors offer high sensitivity, reliable performance, and are cost-effective for large-scale deployment. However, to confirm the sensor’s accuracy following years of use in the field, further studies were needed. In other words, how do these sensors hold up after years of exposure to extreme weather conditions? In the study summarized here – and in further detail in this white paper – Qube Technologies analyzed the long-term accuracy of its sensors following 1-2 years deployed in the field. The team analyzed sensors in both lab and field settings and compared to known standards. The results revealed that Qube Technologies' sensors continue to deliver precise performance, even after long-term exposure to real-world conditions. 

Qube Technologies’ Continuous Monitoring Methane Sensors 

Qube Technologies’ metal oxide sensors detect methane by altering their resistance or voltage when methane molecules react with the sensor's surface. Unique to Qube, each device undergoes multiple calibrations, which involve exposing sensors to known methane concentrations under varying environmental conditions to establish a 'calibration curve'. This allows accurate methane concentration measurements within 1 ppm or 1% of reading, whichever is greater (Figure 2). 

Figure 2 – Lab calibration of a single Qube sensor across a variety of methane concentrations, temperatures, and humidity levels.

Sensor ‘Drift’ Prevented through Qube’s Auto-Baselining Technology 

Metal oxide sensors, while sensitive and reliable, can experience ‘drift’ as they age. This drift occurs when the sensor’s response to methane deviates from its original calibration curve due to environmental impacts on the metal oxide substrate over time. Qube has developed a patent-pending auto-baselining algorithm to address this issue. The algorithm runs continuously in the background, detecting and compensating for drift without any human intervention. 

Validation of Qube’s Methane Sensor Long-term Reliability and Accuracy 

To validate the long-term sensor performance following function in real-world conditions, Qube examined sensors deployed in the field for one to two years. The testing methodology involved a two-part process: 1) laboratory tests and 2) controlled field release tests. 

1. Laboratory Tests 

Laboratory tests were conducted in a temperature, humidity, and pressure-controlled environmental chamber visualized in Figure 3.

Figure 3 – Laboratory setup to test calibration of devices deployed in the field.

A cohort of 26 methane sensors, previously deployed in the Denver – Julesburg (D-J) basin for durations of 1-2 years, were exposed to methane gas concentrations ranging from 0-100 ppm. Testing confirmed that sensors operating in the field responded reliably within their specifications (Table 1). 

Table 1 – Performance summary of re-tested devices in the laboratory.

2. Controlled Release Field Testing 

Field testing was conducted at Qube’s controlled release test facility west of Calgary, Alberta. The sensors were tested to measure known release point, and rates and responses were compared to a Los Gatos Gas Analyzer (LGA; Figure 4). For sources with a release rate of 1.4 kg/hr, the response within the 0-100 ppm range was measured using devices located 10 meters downwind. For a rate of 6 kg/hr, devices placed 5 meters downwind were used to compare the extended range of 100-2,000 ppm. Reinforcing the lab findings, the field studies aligned with the LGA results and validated the sensors' accurate functionality. 

Figure 4 – Comparison of a Qube device deployed in the field against an LGA during a controlled release. Methane concentration measurements from Qube’s sensors align closely with the LGA.

Summary 

The lab and field results confirm that Qube’s sensors achieve exceptional accuracy and reliability over two years of field operation. Importantly, the findings also demonstrate that Qube devices can consistently detect and compensate for baseline drift throughout deployment, eliminating the need for full lab recalibration. This study reinforces a core value proposition of the Qube platform: minimal sensing hardware is required to accurately quantify methane emissions, and the devices remain reliable year after year in the field without manual intervention.