Can a Doppler radar flowmeter be installed under a bridge or inside a box culvert? What space and clearance limits apply?

Yes, but the two scenarios impose very different constraints and must be handled separately.

Bridge-mounted measurement is the classic non-contact installation. The HZ-KSLF sensor is fixed to the parapet or a cantilever bracket with the beam aimed vertically at the water surface; the clearance from sensor to water must stay within 0.5–15 m. Three things to watch: first, the beam footprint has to land on the straight approach reach upstream of the bridge, clear of pier wakes — the zone 3–5 pier-widths downstream of a pier is turbulently disturbed and unusable as a measuring point. Second, on steel bridges with noticeable deck vibration, the bracket needs damping, otherwise wind-induced shake couples into the velocity signal. Third, power and telemetry: bridges rarely have mains supply, so the standard kit is a solar panel plus battery, with 4G backhaul and an EC32 series RTU doing acquisition and forwarding.

Box culverts and closed conduits turn on radar line-of-sight. Inside there is no GPS, no light and often less than 1 m of headroom. The HZ-KSLF still works at low clearance (minimum mounting height about 0.5 m), provided you confirm: the conduit runs partly full — if it flows full, switch to an LGF-PA66 magnetic flow meter for pressurised metering; there is a mounting platform and access hatch in the crown; and the sensor sits on a straight reach at least two conduit-diameters inside the portal where the velocity profile is settled. 4G signal is weak inside culverts, so run an external antenna to the portal, or choose an EC60 series RTU with NB-IoT for extra link budget.

For both scenarios we recommend one manual gauging at commissioning to calibrate the section coefficient into the COSP model before the site goes live.

For more details, visit our product pages or contact our technical team.