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For a radar vs ultrasonic level sensor decision, start with two distances: from the proposed sensing face to the highest water and to the lowest water. Shortlist ultrasonic for a clear, sheltered path where the air column stays reasonably uniform. Give radar priority where temperature gradients or changing vapor make sound travel time unreliable. If a railing or inlet blocks the view of the water, move the mounting point before choosing either instrument.
Which surface will the instrument actually follow?
A buyer usually specifies water depth. An overhead instrument observes the gap to a reflecting surface. A crossbeam, floating cover or patch of foam can give a plausible reading while the water below it moves. Decide what the operator needs to know: the water elevation at a bridge, the liquid level below foam in a basin, or whether water has reached one fixed point. A continuous transmitter makes sense when a trend or changing alarm level matters. A single trip duty needs its own switching and fault-response specification.
Draw the section through the proposed instrument, including everything between its face and the water at the lowest operating level. Show the maximum level separately. Low water usually gives the longest path and widest beam footprint. High water gives the shortest clearance. A unit can pass one test and fail the other, even on a site where the entire water-level swing fits comfortably inside its published range.
What the YEX-HY-RWLS-01 ratings mean at the mounting point
The YEX-HY-RWLS-01 radar water level sensor is a fixed, over-water candidate for continuous monitoring. The model values below were checked against its official product page on 5 November 2026. Apply them to the radar side of the bid comparison. Evaluate an ultrasonic offer against its own transducer, controller and mounting instructions.
| Parameter | Published radar value | Buying decision |
|---|---|---|
| Measuring range | 0.1 to 65 m | Check both face-to-water distances. Allow room for waves and the mounting assembly at high water. |
| Distance resolution | 1 mm | Retain the required precision through the logger conversion. Define a separate error tolerance for the installed station. |
| Typical accuracy | Up to +/-1 mm, subject to installation and target conditions | Compare with an independent water-level reference under the actual surface and bracket conditions. |
| DC supply | 10 to 30 V DC | Calculate voltage drop at the proposed cable length and check the voltage at the head under load. |
| Data connection | RS485 Modbus RTU | Match the RTU port, register definition and scaling. Include a separate telemetry path where remote viewing is required. |
| Mounting | Fixed above water or at tank top | Survey the sensing-face elevation and provide a repeatable position after servicing. |
For example, with the radar face at elevation 104.20 m and a measured vertical gap of 3.10 m, the indicated water elevation is 101.10 m on the same datum. If a replacement bracket raises the face by 0.15 m while the controller keeps the original reference, the displayed elevation reads 0.15 m low. A finer display increment cannot correct that offset. Put the face elevation and the reference used by the staff gauge on the same drawing.
Radar vs ultrasonic level sensor selection at an existing water station
Ultrasonic estimates distance from sound travel time; radar uses an electromagnetic return. Endress+Hauser's technical comparison explains this distinction. In a sunlit tank, the ultrasonic head temperature may differ from the air nearer the water, so local compensation may not represent the whole path. Foam can weaken both acoustic and microwave returns, as VEGA's temperature and foam discussion explains. Performance in foam and condensation depends on the offered model and actual surface conditions.
| Site condition | Ultrasonic consideration | Radar consideration | Purchase or acceptance action |
|---|---|---|---|
| Air path and temperature | Temperature or gas changes can alter acoustic travel time. | Microwaves remove this acoustic sound-speed dependency. | Compare gauge residuals as the air column warms or ventilation changes. |
| Foam and condensation | Foam can weaken returns; wetting or deposits can damp the transducer. | Foam can also weaken the return; the reported surface needs a test. | Define foam-top or liquid-level duty and reproduce normal wet-face conditions. |
| Obstacles and beam | Stray returns can come from a brace within the acoustic field. | Competing echoes still matter; obtain the offered antenna's beam data. | Plot the footprint at low water and relocate the bracket if necessary. |
| High-water clearance | Keep peak level outside the transducer's documented near zone. | Apply the radar model's own minimum usable gap and mounting restrictions. | Check highest water plus waves; measure clearance from the sensing face. |
| Site acceptance | Compare readings through filling, drawdown and temperature changes. | Check the same levels, datum and reporting interval. | Record residuals and test lost echo separately from communication failure. |
| Existing ultrasonic station | Keep a station that meets the revised duty and documented checks. | Change technology when it resolves a demonstrated site limitation. | Price cleaning, relocation and downtime against the complete replacement station. |
Where neither device sees the intended surface, relocate the mounting point first. For a quoted full beam angle, the nominal footprint diameter on a flat perpendicular surface is twice the gap times the tangent of half the angle. Use it to screen obstacles at low water. Objects near the nominal edge can still return echoes.
If overhead access is impractical, compare a submersible liquid level transmitter within the Level Sensors & Meters range. Water contact, sediment and cleaning access then become separate selection conditions.
A sheltered tank and an exposed channel present different tests
Service-water tank with a filling jet
Consider a vented tank with a clear roof opening, stable air temperature and intermittent filling. Start with an ultrasonic candidate mounted away from the inlet. Check a quiet drawdown and a complete refill. A trace that becomes erratic only while the valve is open points first to surface disturbance or splash near the head. Move the test point away from the jet and repeat the same fill sequence before changing technology. At maximum fill, include waves above the nominal operating level when checking the nearest usable distance.
Bridge channel with a crossmember and seasonal low water
At high water a probe may have a clean view below the deck. At low water its footprint can reach a sloping bank or steel brace. Compare the channel gauge and instrument while water recedes. If the indicated distance stops at a value consistent with the brace while the gauge continues to fall, survey the brace position and trial an offset bracket. A radar trial is worthwhile where the air path also changes substantially during the day. Require the new position to pass the low-water geometry check before accepting it.
Prove the water elevation and the lost-echo response separately
Use a rigid mount that can be accessed from a safe service position. Record the face reference, bracket orientation and nearest obstruction before energizing the instrument. Locate the independent reference where it represents the same body of water. Across a gate or close to a pump inlet, a real surface slope can look like instrument error. Pair readings in time and document both locations. USGS Stage Measurement at Gaging Stations, pages 2–4, explains the reference gauge, permanent datum and errors from movement of the supporting structure.
Walk one observation from raw distance through the station calculation to the operator display. As water rises, raw distance decreases and the displayed water elevation should increase. Check units, timestamps and the station identifier on both the local display and the receiving system. For the radar model, the wired interface is RS485 Modbus RTU. Specify the register definition, scaling and serial settings for the delivered unit. Budget the logger, communications link and remote alarm handling separately.
Agree on a usable level tolerance and maximum permissible reporting delay before the trial. At several accessible levels, record gauge reading, sensor distance, computed elevation, weather and operating state. Compare rising and falling observations for lag. Then test loss of communication and loss of a usable echo separately using the supplier's approved procedure. Check whether the operator sees a stale value, an invalid measurement or a fresh alarm. Leave untested seasonal extremes on the acceptance record with a date or condition for retesting. The radar mounting and datum guide covers the installation steps in more detail.
RFQ inputs for a comparable installed price
Include a dimensioned section, photographs looking down and across the beam, the highest and lowest water elevations, and the required reporting interval. Identify foam, condensation, direct sunlight and inlet disturbances by when they occur. For each bid, list the face-to-water operating envelope, beam angle convention, mounting hardware, accessible cleaning position, power at the head and data interface. The acceptance schedule should name the reference gauge, responsible operator, tolerance and response to a missing reading. These details let the buyer compare complete stations on the same duty.
If the required output is discharge, record how level will be converted to flow and over what range the relationship applies. A separate radar flow meter is a different procurement scope for a station that also needs velocity. Name the measured and calculated channels individually when comparing bids.
Project details for radar selection
For a YEX-HY-RWLS-01 station, include the mounting sketch, extreme water levels, headspace conditions, power supply, receiving controller and reference gauge.
Send Your Project RequirementsFrequently asked questions
Q1. Does 1 mm resolution mean 1 mm accuracy at the site?
A1. No. Compare allowable error at the site operating points. Display resolution tells the operator how small a change the instrument can represent. A reading can move in millimetre steps and still carry a larger offset from an incorrect mounting reference. Include the reference gauge uncertainty and the difference allowed at the control threshold in the acceptance sheet.
Q2. Why might an ultrasonic reading change as the tank roof warms?
A2. Sound travel time depends on conditions along the air column. A temperature sensor at the head can experience roof heating while the air nearer the water stays cooler. Record readings against an independent level reference during the transition. If the offset repeats with temperature at constant water level, evaluate shading, a different position or a radar trial.
Q3. Does foam make radar the automatic choice?
A3. Treat foam as a surface condition to reproduce during selection. Its thickness and coverage can change during aeration or filling, and the reported surface may differ from the liquid elevation required for control. Define the reference level beneath or above the foam as appropriate. Compare the candidate during both foam formation and collapse before agreeing to an alarm margin.
Q4. Radar vs ultrasonic level sensor: should a working ultrasonic station be replaced?
A4. Retain it if its range and near-range clearance cover the revised duty and its history agrees with an independent gauge during the difficult parts of the cycle. Review echo losses, cleaning visits and data gaps alongside readings. If trouble occurs only during filling, try a location away from the jet before budgeting a technology change.
Q5. Which candidate belongs on a bridge with limited mounting clearance?
A5. Start with an elevation sketch showing the highest credible water and the nearest fixed steelwork. Compare each offered instrument's minimum usable gap and beam footprint at low water. A narrow footprint may help clear a brace, but model-specific beam data and a trial at the proposed position are needed to judge whether relocation is required.
Q6. Can one station measure tank volume and channel discharge as well as level?
A6. An overhead level station supplies a distance or a level referenced to a datum. Tank volume requires the vessel geometry or a calibrated capacity table. Channel discharge needs an applicable hydraulic relationship or additional measurements. Specify who supplies the conversion, its valid operating range and a means of checking the calculated quantity before adding either output to the equipment schedule.
Q7. What should a purchaser request when the supplier offers a longer cable run?
A7. Specify the cable route, supply at the cabinet, load at the head and receiving equipment. Compare voltage at the device under load with the documented supply limits. For the serial bus, review topology, shielding and termination with the integrator. Demonstrate fresh readings and fault reporting over the installed route before accepting the communication link.
Q8. What can be signed off if peak flood level is unavailable during commissioning?
A8. Record the gauge comparisons and fault tests actually witnessed, together with the water levels covered. Use the survey to document geometric clearance to the design flood elevation and identify the remaining field observation separately. Assign an owner and trigger for that observation so a successful dry-season visit does not become the only evidence for flood operation.
Summary
Choose ultrasonic where the air path and surface give repeatable readings through a complete operating cycle. Shortlist the YEX-HY-RWLS-01 where sound-speed variation is a concern and its mounting and range suit the surveyed site. Resolve obstructions and foam at the actual measuring point. Put the reference elevation, extreme gaps, host interface, reporting delay and witnessed gauge checks in the RFQ so the installed station can be accepted against the decision it supports.
