Remote gas flow monitoring in a biodigester

Aug. 3, 2021
Rugged, compact data logger aids wastewater treatment company

CAS DataLoggers supplied a remote gas flow monitoring data logging solution for a wastewater treatment plant in Sumatra, Indonesia looking to optimize its operation.

The plant used water from a tapiocha starch plant to produce natural gas during its treatment process. However, the plant's staff felt that this gas production could be made more efficient. 

In the natural gas industry, it’s a well-established technique to produce biogas by aerobic or anaerobic "digestion," starting from various biodegradable materials. The gas obtained this way consists of 60-70% methane and can be used to fuel the digester’s boiler and electric generator engines.

The plant’s utilities director decided that the ideal way to increase yields was to monitor and record the biodigester’s gas flow. The biodigester’s gas flow can vary frequently; for example, there was usually a strong momentary increase in gas production immediately after feeding the digester, and seasonal variations in temperature could also inhibit production regularly. Consequently, controlling the feed rate could improve the plant’s efficiency.


The monitoring system that CAS installed consists of an industrial data logger connected to two gas flow meter sensors. CAS’s choice of system was heavily influenced by the installation environment and the properties of the gas measured:

  1. A compact, self-contained weatherproof logger was required to deploy the device outside. The loggers also needed an internal battery for power, since AC power was not readily available at the site, and needed to have cellular communications capability since neither Ethernet nor WiFi were available at the site. For these requirements, CAS chose its dataTaker DT90L, because it offered an IP67 rated enclosure and operated over a temperature range of -40 to +70C. An internal 48W-h lithium battery allowed for extended operation, and it could be connected directly to a 12V solar panel to recharge the battery for continuous operation. An integrated cellular modem allowed data transmission and alarm notification via SMS messaging.
  2. The gases were mainly composed of methane and carbon dioxide, but hydrogen sulfide and wet vapor were also present. Since these latter gases can have corrosive effects, technicians had to use specific flow sensors. In this case, CAS chose two BFM mass flow meters. The flow meters were connected to the DT90’s 4-20 mA analog inputs. One monitored the digester output, and another measured the methane used by the boiler. Each flow meter had two 4-20 mA outputs: one for the gas flow and another for the temperature.

Standalone Operation and Alarm Transmission

This DT90L data logger, housed in a rugged 160 x 100 x 80 mm powder-coated aluminum enclosure, has a powerful 32-bit CPU with 16 MB of non-volatile storage for up to 500,000 measurements that provide for extended autonomous data logging capability.

Additionally, the device’s electronic circuits are designed to reduce the power supply requirements to a minimum so that it can operate for up to 300 days using the internal battery pack. A small 2W solar panel connected to the data logger recharges the battery to provide continuous operation year-round.

The logger has up to eight analog inputs that can accept voltage or 4-20 mA current signals. Via the configuration software the measurements can easily be scaled to the correct engineering units along with high and/or low alarm limits. The measurement rate can be set from once a second to once a day. The logger also provides a switched 5/12V excitation source to power external sensors.

The SAS-based alarm is performed by the DT90L’s internal 4G modem. The data logger can be configured to send SMS alarm messages and FTP measured data. While users mainly rely on the logger’s wireless connection transmit the measurement data, it’s also possible to download data using USB if desired.

Data Access from Smartphone and Tablet

The Datataker Live Cloud Web Portal allows users can remotely monitor the plant online via smartphone or tablet. Users can drag and drop widgets to configure and build custom dashboards that display critical information from any device.


The DT90L data logger had both the necessary durability and small footprint for this deployment. The rugged, weatherproof construction plus the internal battery allowed it to be deployed in a harsh, remote environment, and the Cloud service enabled remote monitoring and mimic generation. These features helped the director fine-tune his process and improve yields.

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