Meteorological Cooperative of the Republic

Weather, climate, seismicity, landslide and flood · mandate held under the organic law on observation and warning

Meteorological Cooperative › Developers › Sensor and station hardware

Sensor and station hardware

Every station the cooperative operates is documented well enough to be built again. The repository holds circuit boards, firmware, enclosure drawings, mounting details and a bill of materials for each class, together with the calibration procedure. The designs use parts obtainable inside the Republic and tolerate substitution where a part becomes unavailable.

Repositorysrc.meteo.rof/rep-station: KiCad boards, C firmware, mechanical drawings, calibration procedures
Design ruleParts obtainable inside the Republic, with a stated substitute for each
Service lifeTwenty years for the enclosure, ten for the electronics
PowerMains where present, otherwise solar with four days of battery reserve
TimeSatellite time with a disciplined oscillator; 2 ms holdover for 24 hours
RepairThrough-hole where a technician may need to work in the field

Station classes

Documented station designs
Class Sensor Sampling Power Enclosure
Strong motion Three-axis MEMS accelerometer, ±4 g 200 Hz 1.8 W Cast box bolted to a floor slab or a pier
Broadband seismic Three-component velocity sensor in a sealed vault 100 Hz 4.5 W Buried vault, thermally isolated, on bedrock where available
Rainfall Tipping bucket, 0.2 mm, with a heated funnel Per tip 0.4 W, 26 W heated Post-mounted, aerodynamic rim
River stage Radar level sensor above the channel 1 min 0.9 W Bridge or gantry mount clear of debris
Tide gauge Pressure transducer in a stilling well, with a radar check 1 s 1.2 W Well set into the quay, with an access hatch
Soil moisture Capacitance probes at three depths 5 min 0.3 W Buried, with a surface junction box
Slope probe Wire extensometer, tilt sensor, vibrating-wire piezometer 1 min to hourly 0.7 W Anchored to rock or to a driven pile
Surface synoptic Temperature, humidity, pressure, wind, radiation, visibility 1 s to 1 min 6 W Screen and mast to the standard dimensions
Receiver board Broadcast and data receiver with the wire decoder Event driven 0.2 W Module for embedding in other equipment

The seismic station in detail

Detection time governs everything REP-KJS achieves, so a fork will spend most of its hardware effort here. Three parts determine the performance: the sensor, the timing and the link.

The strong motion station uses a three-axis MEMS accelerometer sampled at 200 Hz through a 24-bit converter. Noise floor is about 30 micro-g per root hertz, which is adequate for intensity and inadequate for locating small events. The broadband station handles the second task, and the two are deployed together at 21 sites on the margin.

Timing comes from satellite time with a temperature-compensated oscillator disciplined to it. Arrival times are the basis of every location, so a station clock 400 ms out corrupts the estimate for every event it contributes to. The firmware reports its own time uncertainty in each packet, and the issuing node discounts any station reporting above 20 ms.

Triggering happens at the station. Sending continuous data from 296 seismic stations would exceed the links available in the upland, so each station computes its own trigger and sends a short packet on firing, followed by the first seconds of the record. Continuous data flows from the 21 margin sites only, where the links support it.

Cost of the seismic network in material

A strong motion station is roughly 340 items on the bill of materials, of which the accelerometer, the converter and the timing receiver dominate. The remainder is enclosure, mounting and power.

The design was constrained to parts with at least two sources and a stated substitute for each, because the whole network was built during a period when the external catalogue was narrowing. Four substitutions have been made since 2021, and each is recorded in the repository with the calibration difference it introduced.

Siting

The drawings state where a station may stand, and the constraint differs by class. A strong motion station must sit on ground representative of the settlement it reports for, since an instrument bolted to rock beside a town built on sediment will understate what the town experiences. A rainfall gauge must stand clear of obstacles by at least twice their height. A river gauge must be clear of the debris line and above the highest recorded stage.

Departures from the siting rule are recorded in the station metadata and published, so a user can judge a series against the conditions it was measured in. Eleven stations in the network sit in positions the rules would exclude, mostly for want of any alternative in the sub-region.

Calibration

Calibration intervals
Class Interval Method Record
Strong motion Yearly Shake table against a reference instrument Response curve published per station
Broadband seismic Yearly Step response through the calibration coil Published with the poles and zeros
Rainfall Six months Volumetric, at three rates Correction factor per gauge
River stage Six months Staff gauge comparison, plus discharge gauging twice a year Stage-discharge relation republished
Tide gauge Yearly Levelling to the benchmark; datum check Datum history published with the series
Slope probe Two years Known displacement applied to the wire Zero and scale recorded

Building one

The repository holds enough to build a station without asking anybody. Clone src.meteo.rof/rep-station. Board files open in KiCad, the firmware compiles with an ordinary toolchain, the mechanical drawings are dimensioned, and the bill of materials names each part with its substitutes. The calibration procedures state the equipment required and the tolerance to be met.

What the repository cannot supply is the local information. A fork must establish its own ground-motion model, its own soil map, its own station spacing and its own thresholds. Those are the subject of the porting guide.

See also