About the Recording Telemetry Unit (RTU)

As described above, an RTU is installed at a monitoring site for the purposes of collecting and recording measurements as detected by various types of sensors connected to the RTU. An RTU is capable of recording different types of data:

  • Analog trend data measured over time, flow, depth
  • Individual events, for example pump start/stop, rain gauge tipping
  • High frequency impulse data - most commonly for pressure transient events in pressurized water mains.

Not all RTUs can manage these different types of data, and many RTUs are designed with a specific application in mind. For example, hydrant pressure recorders, flow meters, level, etc.

RTUs have channels which are connected to specific sensors. Some specialist RTUs have just a single channel, others are complex RTUs that have multiple channels, to capture and record sensor measurements from multiple sensors that typically may be used at a larger site such as a pumping station or a treatment works.

RTUs are typically located in rugged enclosures, which, depending on the environment they will be installed in, will be protected from water and dust ingress.

For most RTUs the battery, and battery life is one of the key considerations for the RTU and its configuration. Usually a balance has to be struck between frequency of call in, sample rate and recording interval. Obviously, the higher the battery drain, the more frequently field crews will need to be scheduled to replace the battery, however typically a battery will last for a number of years. Some RTUs have power supplied via solar panels, in which case the onboard battery becomes more of a backup power source.

Another external component of those RTUs that will communicate via cellular or LoRaWAN networks is the antenna. The requirements for the antenna will be partly determined by the strength of the cellular signal, but also the installation location of an RTU, for example down a manhole. In some cases the antenna can be built into the existing infrastructure such as a manhole cover.