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Select a backwash water turbidity sensor that covers required peaks and resolves lower comparison values. YEX-S1-TS offers 0–20, 0–200 and 0–1000 NTU options. Use representative wash-cycle evidence to shortlist the range, then verify performance, installation conditions and overrange handling before ordering.
Backwash water carries retained material out of the filter during cleaning. Specify both the NTU span and the wash stages to record.
This guide addresses discharged washwater and equipment selection. For decisions about the filtered water returned to service, use the separate filter-to-waste endpoint guide. A useful washwater trend does not by itself demonstrate acceptable service-water quality.
Buyer risk: selecting from the clean end of the cycle
Selecting from a clean late-wash sample can exclude the early discharge peak. A wider range, however, does not prove adequate low-level accuracy. Specify both ends of the required measurement.
A repeated ceiling may come from the sensor or PLC; a stalled update can also look flat. Check raw values, range settings and timestamps before treating a plateau as a measured peak.
State whether the channel compares wash cycles or investigates abnormal discharge. Neither water savings nor solids removal can be established from turbidity alone.
Verified S1-TS parameters and their purchasing implications
The official YEX-S1-TS product page supports the following parameters, checked 23 October 2026. Request the matching datasheet and register map before ordering.
| Parameter | Official S1-TS information | Decision for this duty |
|---|---|---|
| Range options | 0–20 / 0–200 / 0–1000 NTU | Compare the required lower interval and observed peaks with the proposed option. Request another documented configuration if necessary. |
| Optical principle | 90° infrared scattered light | Validate the response in the actual washwater; do not treat NTU as a universal solids-mass conversion. |
| Output | RS485 Modbus RTU | Obtain data type, scaling and status behavior. An analog interface is not established by this specification. |
| Supply | 12–24 V DC | Confirm the installed supply and the ordered version’s consumption before panel sizing. |
| Mounting and protection | Immersion; NPT 3/4; IP68 | Check wetting, access and mechanical support. Obtain pressure limits before specifying a flow cell. |
| Standard cable | 5 m four-core shielded cable | Compare with the actual route and obtain approved extension details. |
| Accuracy, resolution and response | Not quantified in the cited specification table | Request the matching model documentation and evidence at the intended observation levels. |
| Materials, pressure and temperature | Obtain exact configuration limits | Check wash chemicals and maximum exposure; do not substitute another model’s limits. |
How to select a backwash water turbidity sensor
| Approach | When it helps | What the quotation must establish |
|---|---|---|
| One channel covering the required cycle | Both important peaks and lower observations can be measured adequately by one documented configuration. | Performance across the required interval and clear handling of any excursion beyond it. |
| A deliberately bounded observation interval | The project only needs a stated part of the wash cycle, such as a repeatable late-wash comparison. | Which stages are excluded and how the record prevents an excluded stage from being treated as valid evidence. |
| Separate measurement duties | The project needs both a dirty-washwater record and a sensitive filtered-water observation. | A separate specification, location and acceptance method for each channel. One range label cannot establish both duties. |
| Further survey before selection | Existing samples do not capture representative peaks or the particle conditions vary substantially. | A survey scope and a selection hold point before hardware is committed. |
Retain S1-TS when its range, RS485 interface and verified exposure limits meet the duty. Compare another documented configuration only for an unmet requirement. Do not infer wider range from S1PRO or S2, and do not recommend the stainless-steel S1PRO configuration for seawater.
Worked range-selection example
Illustrative values only: a survey records 8–650 NTU during the required wash stages. The 0–20 and 0–200 NTU options cannot cover that span. The 0–1000 NTU option is a candidate, subject to verified performance at 8 NTU, peak response and chemical compatibility.
Request evidence at the lower comparison level and upper operating region, plus documented overrange behavior. If a required stage reaches 1500 NTU, none of the listed S1-TS ranges covers it. Specify another verified solution or explicitly narrow the objective; an off-scale ceiling is not the actual peak.
Set headroom from credible variation and the consequences of missing an excursion.
Build a useful wash-cycle survey
Survey representative loading conditions, including early discharge. Retain filter identity, wash stage, timestamp and flow; flag air scour, an empty channel and maintenance. Sampling only after the water clears cannot establish peak coverage.
Take reference samples at the same hydraulic point and align their time with online observations. Agree the reference method, handling and instrument range. A delayed grab sample cannot establish an earlier short peak; retain excluded comparisons with reasons.
Separate measured stages from off-scale stages. A bounded record can support a bounded comparison, but cannot quantify an unmeasured peak.
Field scenarios that change the purchase specification
Industrial reuse polishing: production changes can alter particles entering the filter. Compare wash cycles under identified production states to avoid attributing a different influent to a change in cleaning performance.
Multi-vessel skid: a common drain may combine discharges. For vessel-level comparisons, specify individual measurement or demonstrate a sampling schedule that captures each required interval without carryover.
Intermittent trough: a convenient location may empty between cycles. Define when the probe stays wetted; include bypass start-up, flushing and draining in the scope. These scenarios are illustrative engineering arrangements.
Installation and integration must preserve the event
Choose a representative wetted location with retrieval access and mechanical protection. Check deposition, air and debris before adding averaging. A bypass adds transport delay and possible settling; conditioning must preserve the particles being observed.
USGS turbidity guidance explains how particle characteristics and bubbles affect optical readings. This measurement background does not certify a particular installation.
Verify the RS485 register map, units, scaling and update behavior against the delivered device. Compare device and host values. Obtain the actual overrange behavior instead of assuming that a maximum number or an undocumented status code identifies it.
Log wash stage, filter identity, maintenance state and communication age with the value. Define host or operator checks for missing diagnostics. Demonstrate that logging and averaging preserve the required event and distinguish unavailable data from valid low readings.
RFQ checklist and acceptance evidence
| RFQ item | Information to provide | Evidence to request |
|---|---|---|
| Water and cycle | Source, filter arrangement, wash stages, relevant chemicals and representative observations. | Written compatibility and a range recommendation tied to the stated duty. |
| Measurement objective | Required peaks, lower observations and any intentionally excluded interval. | Matching accuracy, resolution and response documentation plus a field verification plan. |
| Installation | Drawing, wetting conditions, access, cable route and maximum exposure. | Mount or cell scope, operating limits, flow supervision and service requirements. |
| Controls | Supply, host interface, historian needs and maintenance handling. | Register map and demonstrated treatment of overrange, stale data and communication loss. |
| Commercial scope | Quantity, destination, spares, delivery needs and commissioning responsibilities. | Itemized inclusions, exclusions, support terms and the agreed acceptance record. |
Agree reference comparisons, representative cycles and fault tests before purchase. Preserve as-found results before cleaning or adjustment, then repeat the relevant check. Bench communication alone does not establish field performance.
Acceptance record: retain filter, stage, sample time and location, reference result, online result and quality status. Calculate online minus reference in NTU. Compare against an agreed criterion reflecting method, uncertainty and purpose. Align rapidly changing samples before interpreting the difference; there is no universal acceptance percentage.
Sources and evidence boundaries
YEX-S1-TS specifications support the model table; USGS turbidity guidance supports the interference discussion. Examples are illustrative. Confirm unlisted accuracy, response and operating limits in the matching model documentation.
Review the measurement package
Send the washwater source, filter count, cycle sequence, NTU records, installation drawing, maximum exposure, interface, cable route, quantity and destination. Identify the required comparison and commissioning responsibilities.
Review the YEX-S1-TS range and integration specifications and Send Your Project Requirements.
Frequently Asked Questions
Q1. Why can a backwash turbidity trace flatten at its upper limit?
A flat upper trace may indicate an instrument or host limit, but it can also reflect a steady process value or a stalled update. Compare the raw measurement, timestamps and configured range before deciding. Ask the supplier to demonstrate its actual overrange behavior and require the historian to distinguish invalid or limited data from a valid measurement.
Q2. Can NTU be converted directly to backwash solids mass?
No universal conversion applies. Turbidity depends on optical response, while solids mass requires an appropriate reference determination and the relevant water volume. If a mass estimate is required, define a separate sampling and validation scope. Do not buy an NTU channel on the assumption that a single multiplier will remain valid across different particles and wash conditions.
Q3. Does adding more averaging solve air-scour interference?
Averaging may smooth the display while obscuring a short event. It does not establish whether the original signal came from particles or bubbles. Review the flooded condition, installation and process timing first. Ask for raw and processed data during commissioning, and approve any averaging only after its effect on the intended comparison is understood.
Q4. Does every backwash water turbidity sensor need a 0–1000 NTU range?
No. It is one published S1-TS option, not a guarantee that every dirty-water peak fits. Determine both the peak you need to observe and the lower interval you need to compare. Obtain the matching performance specification; choose another documented configuration if the required measurement cannot be demonstrated within the offered span.
Q5. When should I evaluate the 0–20 or 0–200 NTU options?
Evaluate them when representative evidence places the required observation interval within the proposed span and the specified performance suits the decision. A clean late-wash value alone cannot justify a range intended to record the whole cycle. State any intentionally excluded early interval in the purchase specification so reviewers understand what the channel can establish.
Q6. Should the probe use direct immersion or a bypass?
Use a suitable immersed location when it remains wetted and accessible through the measured interval. Consider a bypass when maintenance access justifies the additional piping, delay and flow supervision. Request a drawing and a field demonstration for the proposed arrangement. Do not assume an immersion rating makes an arbitrary pressurized cell acceptable.
Q7. What should distributors include in an RFQ?
Provide the washwater source, cycle stages, available peak data, required lower-end observation, installation drawing and host interface. Add maximum exposure conditions, cable route, quantity, destination and service expectations. Request separate prices for the probe, sample arrangement, documentation and commissioning, with written confirmation of every model-specific limit used in the selection.
Q8. What should an EPC require before accepting the package?
Require representative cycle records, same-point reference comparisons and a demonstrated mapping of measurement, overrange, maintenance and communication-loss states. Agree the criteria and responsibilities before testing. Include an operator-led inspection or verification task in the handover, so acceptance covers a maintainable measurement channel under actual operating conditions as well as successful bench communication.
Q9. Can this washwater sensor authorize return to service?
Its dirty-water record alone does not establish the quality of the filtered water supplied downstream. Specify the separate outlet measurement and approved release logic for that decision. Buyers who need both functions should price and document each duty explicitly, rather than treating washwater range selection as proof that the service outlet meets its criterion.
Summary
Select the backwash water turbidity sensor against required peaks and lower comparison values. Retain S1-TS where its verified range, interface and exposure limits fit. Confirm representative wetting, sample delay, cable routing and host fault handling. Supply cycle evidence, installation conditions and acceptance responsibilities in the RFQ. Keep filtered-water release under its separate specification.
