Product Overview
The Dynasonics RS-900w is a compact inline, low-flow irrigation flow meter that uses ultrasonic transit-time sensing instead of a paddle wheel or turbine — so there is nothing in the stream to clog or wear in dirty irrigation water, and it holds ±2% of reading on forward flow across a wider range than a mechanical meter, with an extended low-flow band below the normal minimum besides. It plumbs inline in 1, 1-1/2 and 2 in. with female tapered NPT or BSP threads, needs no straight run, and feeds high-pulse-rate irrigation controllers — including the Badger Meter FC-5000 flow display — over a 2-wire pulse / power loop, with on-board LEDs for power, forward and reverse flow. The all-polymer, glass-filled-nylon body is rated to 200 psi at 32–140°F (0–60°C) and built to IP68 / NEMA 4X for outdoor and briefly-submerged service.
Other Dynasonics options for different needs
E-Series G2 — inline lead-free-bronze water meter
TFX-500w — clamp-on water meter
Key Features & Benefits
- Built for high-pulse-rate irrigation controllers — the pulse / power output drops straight onto modern high-pulse-rate irrigation controllers — including the Badger Meter FC-5000 flow display — and three on-board LEDs read out power, forward flow and reverse flow right at the meter
- More accurate over a wider range than a mechanical meter — ultrasonic sensing holds ±2% of reading across a broad flow range and an extended low-flow band, where a turbine or paddle-wheel meter loses accuracy at the low end
- Nothing in the stream to clog or wear — with no rotor or bearing in dirty irrigation water, there is no moving part to foul, stall or replace — low maintenance over a long service life
- Drops into tight irrigation manifolds — no straight-run pipe to find — the single-piece threaded body fits the valve-and-fitting layouts typical of irrigation skids
- All-polymer, weatherproof and submersible — the glass-filled-nylon flow path resists corrosion, and the IP68 / NEMA 4X build takes outdoor and even briefly-submerged installations in stride
Specifications
- Measurement principle
- Ultrasonic transit-time — the sensor transmits an ultrasonic signal through the flowing water; the difference in transit time between the upstream and downstream paths is proportional to flow velocity.
- Accuracy
- ±2% of reading on forward flow across the normal flow range. Below the normal minimum each size also reads an extended low-flow band, specified to an absolute tolerance — ±0.05 gal/min (1 in.), ±0.13 gal/min (1-1/2 in.), ±0.20 gal/min (2 in.)
- Flow range / velocity
- Size-dependent normal range: 1 in. 1.30–50.0 gal/min (4.92–189 L/min), 1-1/2 in. 3.09–125 gal/min (11.7–473 L/min), 2 in. 5.13–200 gal/min (19.4–757 L/min). Each size adds an extended low-flow band below that minimum — down to 0.26 gal/min (1 in.), 0.62 gal/min (1-1/2 in.) and 1.03 gal/min (2 in.)
- Pipe sizes
- 1, 1-1/2 and 2 in. female tapered thread
- Installation
- Single-piece threaded body that plumbs inline with female tapered NPT or BSP connections; may be mounted horizontally or in vertical pipe and can be installed submerged (under 3 ft of water for up to 24 hours)
- Straight-run requirement
- No straight-run requirement — unlike a turbine or paddle-wheel irrigation meter, the RS-900w needs no fixed run of upstream / downstream pipe, so it fits tight valve-and-fitting irrigation manifolds where straight pipe is scarce
- Compatible fluids
- Irrigation and similar clean water; rated for a 200 psi working pressure at a fluid temperature of 32–140°F (0–60°C)
- Wetted materials
- Glass-filled nylon body with a polyphenylene-oxide upper — an all-polymer flow path with no metal wetted parts to corrode in irrigation water
- Ingress / environmental rating
- IP68 / NEMA 4X, suitable for outdoor service and for submerged installation (under 3 ft of water, 24 hours); altitude under 2000 m (6560 ft), humidity 0–90% non-condensing
- Outputs
- 2-wire pulse / power output (the same two conductors carry power and the flow pulse), 0.5–200 Hz output frequency, 5 msec pulse width; the shielded PTLC cable connects to a display, monitor or controller
- Power
- 8 V DC minimum, 28 V DC maximum on the 2-wire loop, ~600 µA quiescent current
Common Applications
- Agricultural irrigation — field and crop water delivery
- Golf-course irrigation
- Commercial turf, landscape and municipal irrigation
- Irrigation pump stations
- Water-district metering of irrigation deliveries
The RS-900w is purpose-built for clean irrigation water in 1–2 in. line. For a larger water main, a clamp-on TFX-500w reads from outside the pipe; for a permanent metered point that needs the tightest low-flow accuracy and NSF potable listing, the inline lead-free-bronze E-Series G2 is the go-forward water meter. Use the input form to send your line size and flow range and we’ll confirm the meter.
Design & Selection Considerations
- Match the method to the fluid — transit-time vs Doppler — transit-time meters time an ultrasonic pulse sent with and against the flow, so they want a clean to lightly-laden liquid that passes sound (the TFX-5000 clamp-on and E-Series G2 inline). A Doppler meter (the DFX) does the opposite — it needs suspended solids or aeration to reflect the signal, which is what makes it the pick for sewage, slurries and aerated fluids. Use the input form to tell us how clean the fluid is and the right principle follows; the wrong one simply will not read.
- Clamp-on or inline — non-invasive vs best low-flow accuracy — a clamp-on meter straps transducers to the outside of the pipe — no cut-in, no pressure drop, no wetted parts, and it installs on a live line (the TFX-5000 / TFX-500w, and the portable DXN-5P). An inline spool (E-Series G2) is a permanent wetted body that holds the tightest low-flow accuracy and carries potable-water approval. Retrofit and survey work favour clamp-on; a permanent metered point with tight accuracy favours inline.
- Clamp-on needs a sound-friendly pipe — a clamp-on meter sends sound through the wall, so it wants a solid, sonically-conductive pipe of known material and wall thickness — metal and most plastics read well; heavy mortar lining, fibreglass, gas pockets, or badly corroded / scaled wall scatter the signal. Use the input form to give us the pipe material, OD and wall and we confirm suitability and transducer choice. The pipe is part of the meter on a clamp-on install — spec it as carefully as the fluid.
- Give the meter a developed flow profile — ultrasonic meters tolerate less straight run than a turbine, but a swirling or distorted profile off elbows, pumps and valves still biases the reading. Allow the recommended upstream / downstream straight run, or mount on the longest available run. More straight run, steadier reading — design the location, do not just clamp where it is convenient.
- Specify potable / hygienic approval where it is required — for drinking-water service the body must be lead-free and certified — the inline E-Series G2 carries a lead-free bronze body to NSF/ANSI 61 & 372. Say up front that the line is potable and we specify an approved body, not a general-purpose one. Approval is a build choice, not a field add-on.
- For heating / cooling energy, pair flow with a matched RTD pair — thermal energy is flow × the supply-return temperature difference, so an energy meter needs a matched temperature-sensor pair as well as flow. The UHC-120 integrates ultrasonic flow with the RTD pair to EN 1434, and the FC-215 computes energy from an external flow signal and RTD pair. For BTU / tenant billing, the matched sensor pair and the standard matter as much as the flow reading.
- Open channel: non-contact level or submerged area-velocity — in an open channel, flow is derived from level over a known primary device, or from velocity × area. The IS-4000 reads level non-contact over a flume or weir — nothing in the stream to foul; the IS-6000 submerges an area-velocity Doppler sensor where there is no primary device or the channel surcharges. A flume / weir site suits non-contact level; a surcharging or primary-less channel suits area-velocity.
To size & select the right Dynasonics RS-900w:
Use the input form to send your pipe size and material (or line size), the fluid and how clean it is, the flow range and accuracy target, and the fluid temperature — with whether you need clamp-on or inline, energy / BTU, or open-channel — and we’ll spec the right Dynasonics meter, transducers and outputs for your application.
Flow Meter Application Sheet ›Talk to an engineer directly — Scott Prater, Principal · 917-580-0878 · scott@pratertechnical.com
Specifications compiled by Prater Technical Partners from Badger Meter Dynasonics ultrasonic flow product literature.