Custom Multi-Channel IoT Dataloggers

Versatile in house dataloggers for research and industrial monitoring. A single unit reads analog inputs (4-20mA and 0-10V), digital sensor buses (SDI-12 and RS-485 Modbus) and pulse or counter inputs, stores data on board and sends it on over LoRaWAN or Sigfox. Industrial grade components and configurable sampling make them suited to demanding, unattended field sites.

How it works

Sensors connect to the logger through the input type that suits them: a two-wire 4-20mA transmitter, a voltage output, a pulse output, or a digital bus such as SDI-12 or RS-485. The logger samples each channel on its own schedule, applies calibration, time-stamps and stores the readings, then transmits them to your server or dashboard. Power is managed for solar or battery operation so the unit runs unattended for long periods.

Inputs and connectivity

[ Analog ]	4-20mA current loops and 0-10V voltage inputs for transmitters and analog sensors.
[ Digital ]	SDI-12 sensor bus and RS-485 Modbus for intelligent digital sensors.
[ Pulse ]	Pulse and counter inputs for tipping buckets, flow meters and anemometers.
[ Telemetry ]	LoRaWAN and Sigfox, with local storage so data survives a dropped link.
[ Build ]	Industrial grade components, configurable sampling rates and solar or battery power.

The logger sends data over the LoRaWAN and Sigfox low power wide area networks.

Hardware specification

The logger is built around a proven microcontroller with local storage, accurate timekeeping and an onboard modem, and it brings every field connection out to screw terminals for quick, reliable wiring.

Processor	Low power microcontroller with an on-board programming header for firmware loading and field updates.
Real time clock	Battery-backed real time clock for accurate time-stamping of every reading, even after a power loss.
Local storage	Removable memory card for on-board logging, so data is retained if the telemetry link drops.
Communications	Onboard modem for LoRaWAN and Sigfox communications.
SDI-12	Dedicated SDI-12 sensor bus for intelligent digital environmental sensors.
Analog and digital I/O	Analog inputs and digital input and output pins for a wide range of sensors and control lines.
Pulse input	Pulse or counter input for tipping-bucket rain gauges, flow meters and anemometers.
Power input	5 to 12 VDC supply input, suited to solar and battery installations.
Regulated outputs	Switched 3.3 V, 5 V and 12 V outputs on screw terminals to power connected sensors.
Field wiring	Screw terminals throughout for sensor connections, power in and regulated power out.
LED indicators	Status LEDs for power, programming activity and data transmission through the modem.

SDI-12 sensor support

Our loggers speak SDI-12, the serial protocol that has become the standard way to connect intelligent environmental sensors to a logger. SDI-12 (Serial Data Interface at 1200 baud) was created in the late 1980s by a group that included the United States Geological Survey to make it simple and reliable to read digital sensors in the field. It uses a client and server model: the logger is the recorder, and each sensor on the bus has its own address and answers when it is called.

How SDI-12 works

Three-wire bus	One wire for data, one for ground and one for power, so the same cable powers the sensor and carries its data.
Addressed sensors	Every sensor has a unique address, so many sensors share one bus and the logger talks to each in turn (half duplex).
Standard commands	A defined command set requests measurements, runs sensor tests and sets parameters, with sensors replying in readable ASCII.
Low speed by design	The fixed 1200 baud rate keeps wiring simple and robust over long cable runs, which suits slow-changing environmental readings.

Why we use SDI-12

[ Interchangeable ]	Sensors can be swapped without reprogramming the logger, so a site is easy to expand or repair.
[ Low power ]	Designed for battery and solar sites with very low current draw between readings.
[ Noise resistant ]	Digital signalling shrugs off the electrical noise that corrupts analog readings, improving data quality.
[ Interoperable ]	Sensors from different manufacturers work together on one bus, so you are not locked to one brand.
[ Self-describing ]	Intelligent sensors can self-calibrate and report their own identity and metadata, cutting setup and maintenance.

Standardised digital sensing is why the environmental market has moved steadily from older analog wiring to SDI-12: it is simpler to install, easier to maintain and more reliable over the long life of a monitoring station. Where a site already runs a PLC or an established logging system, we can bridge SDI-12 sensors into it or fall back to RS-485 Modbus or analog inputs as needed.

Standards: SDI-12 Support Group · Modbus over RS-485

Applications

Environmental	Weather stations, water quality (pH, dissolved oxygen, conductivity), soil moisture arrays and hydrological monitoring.
Industrial	Process monitoring, tank and level measurement and multi-sensor plant data acquisition.
Research	Custom sensor combinations and sampling schemes that off-the-shelf loggers cannot cover.

Deploy a datalogger system

We design, build and support loggers around your sensors and site. Contact us for more information and to discuss deploying a custom datalogger →

Related: More technologies we build →

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