There are various methods for measuring the presence of methane gas. My favorite is the laser-based absorption spectroscopy method. That’s what my PhD is in. Sometimes though, there are simpler “off-the-shelf” methods for measuring this invisible, naturally odorless, and valuable gas resource.
The table below contains a list of commercially available sensors you can use to measure methane gas concentration. Some of these sensors are extremely affordable. Here I go through some of the selection criteria I use in deciding on a methane sensor module for customer projects.
Methane Sensor Selection Criteria
An amazon search these days will pull up a long list of natural gas detectors for typical household leaks. For process or environmental monitoring applications, however, I typically start with the methane concentration as the guiding factor in deciding on a sensor module. The question is, what are the reasonable maximum and minimum methane concentrations your sensor will experience during your measurement process?
Most sensors have a detection ceiling of 5%, which is methane’s lower-flammability-limit (LFL). Though there are many cases where you’ll need to measure methane levels above the 5% limit. The detection range should bookend the range of methane concentration you expect to encounter in your sensing environment.
Similarly, most sensor modules will operate at typical electronics operating temperatures, -10 – 50 °C. In chemical process or combustion related applications, temperatures can reach well beyond 100 °C.
The response time of the sensor is then my next consideration. Do you need to make measurements every 5 ms or at least once per minute? Most sensors on the market now have a response time of under 1 min. Custom tunable diode laser absorption spectroscopy (TDLAS) systems can deliver measurements on the order of 1 microsecond. My experience with these is in lab/bench level scientific instrumentation.
Instrument accuracy is another major consideration when choosing a sensor module. Sometimes you just need a qualitative measure of the methane, e.g. are the methane levels increasing or decreasing? Most of the time, though, you need to measure methane concentration as a small part of the overall data stream you need to generate to monitor or optimize your gas flow process.
A full assessment of the best sensor module will also include mechanical design, manufacturing, electronics, data acquisition, and network considerations. Table 1 below contains some of the typical methane sensor modules I consider when designing a new system.
Vendor/Brand | Product Link | Sensor Type | Detection Range | Price | Accuracy | Response Time | Data Output |
SparkFun | Metal-oxide | 300 – 10,000 ppm | $6.94 | Not Stated | ~ 10 s | Analog (4.0 V) | |
Vaisala | Not Stated | 0 – 5% vol. | Not Stated | +/- 5% | 90 s | RS-485/4-20 mA | |
eLichens | NDIR | 0 – 5% vol. | $273 | +/- 5% | < 30 s | UART | |
Senovol | TDLAS | 0 – 5% vol. | $368 | +/- 3% | < 25 s | I2C/UART |
Table 1 – Typical options for commercial off-the-shelf methane sensor modules
Book a call here and I’ll help you figure out your methane gas sensing needs. We have space for one additional gas sensing project onboarding this month.
