YEX-S2-NHN-A Ammonium Nitrogen Sensor | RS485 & 4-20mA

YEX-S2-NHN-A is a flagship-series online ammonium nitrogen sensor with a dual-interface design (RS-485 Modbus RTU + 4–20 mA), built for wastewater treatment plants, aquaculture farms and irrigation projects that need ammonium data in both digital SCADA networks and legacy analog control loops. It uses ion-selective electrode (ISE) measurement with automatic temperature compensation and continuous online reporting — no reagents, no sampling lag.

S2 Series Positioning: The Flagship Tier of the YexSensor Line

The YexSensor online water quality family is organized in three tiers: the S1 standard series (cost-effective plastic-housing probes for high-volume monitoring points), the S1 PRO stainless-steel series (316L housings for corrosive duty), and the S2 flagship series — the top tier, designed around dual-interface connectivity, extended configuration freedom and OEM-level support.

Ammonium control is the most operator-intensive measurement in biological treatment: aeration setpoints, return-sludge rates and discharge permits all depend on it. The S2-NHN-A is engineered to put that measurement directly into both the control layer (4–20 mA loops, PID dosing) and the data layer (Modbus RTU to SCADA, historians and cloud platforms) from a single ISE probe.

Core Technical Highlights

• Dual-interface connectivity: RS-485 (Modbus RTU protocol) for PLC, RTU, data logger and IoT gateway integration, with 4–20 mA output support for conventional analog loops — one probe covers both architectures.

• Reagent-free ISE measurement: ion-selective electrode technology eliminates chemical consumption and sampling lag, keeping operating cost low and data continuous.

• Selectable ranges: 0–10.00 mg/L and 0–100.00 mg/L ranges to match low-ammonium discharge points and high-load inlet monitoring alike.

• Automatic temperature compensation: built-in temperature channel stabilizes ISE readings across seasonal temperature swings.

• Submersible IP68 construction: continuous immersion in aeration basins, ponds and channels, with NPT 3/4 thread installation for pipes and flow cells.

Application Scenarios

1. WWTP aeration control: track ammonium valleys and peaks to drive blower setpoints and dosing pumps, cutting aeration energy while protecting the discharge permit.

2. Discharge compliance: continuous nitrogen records at the outfall for regulatory reporting and early warning before limit excursions.

3. Aquaculture and RAS: toxic un-ionized ammonia surveillance in ponds and recirculating systems, alongside DO and pH sensors on the same bus.

4. Irrigation and livestock wastewater: nutrient-load monitoring for fertigation balance and lagoon management.

Technical Specifications

Contact our engineering team for the full datasheet, register map and application-specific configuration options before ordering.

Engineering Selection and Integration Notes

Measurement meaning and selection boundary

Ammonium (NH4+) and un-ionized ammonia (NH3) are different quantities — the fraction of un-ionized ammonia, which is toxic to fish, depends strongly on pH and temperature. Confirm which quantity your permit or biology decision actually needs, and whether potassium interference compensation is relevant for your matrix, before setting acceptance limits. ISE sensors report ammonium activity as a surrogate correlated to your local reference method; establish a site baseline against laboratory analysis at commissioning.

Installation and maintenance

Install at a representative, continuously wetted and well-mixed point, fully immersed to at least one third of the probe length. ISE membranes require periodic inspection and cleaning — keep the sensing area free of biofilm and debris, and verify against the agreed laboratory method after cleaning or process changes. The sensor is calibrated before delivery; perform zero or slope calibration per the register-map procedure when drift data requires it.

Frequently Asked Questions

What makes the S2-NHN-A different from the YEX-S1-NHN?

Both use reagent-free ISE measurement with RS-485 Modbus RTU output. The S2-NHN-A belongs to the flagship tier and adds 4–20 mA output support in the same probe — designed for plants that run mixed digital/analog architectures, retrofit projects with existing PID dosing loops, and OEM panels that need one SKU for both worlds — with extended configuration freedom and OEM-level engineering support.

How often does an ISE ammonium sensor need calibration?

Typical practice is monthly slope verification with standard solutions, adjusted from your drift data; high-fouling wastewater may need more frequent checks. Compare against laboratory results at commissioning and after major process changes to anchor the correlation.

Can one probe feed both my SCADA system and the existing dosing controller?

The S2 series is designed as a dual-interface product for exactly this situation. Wiring availability depends on the ordered configuration, so confirm your cabinet architecture with our engineers when requesting a quotation — we will provide the exact wiring diagram and Modbus register map for your order.

Which range should I order — 0–10 or 0–100 mg/L?

Match the range to the water and the season: discharge points and aquaculture typically use the 0–10 mg/L range for resolution, while raw inlets and lagoons need the 0–100 mg/L range to avoid saturation. If your load varies across both, discuss dual-range strategy with our engineers before ordering.

What quality assurance is provided?

Every unit passes a standardized inspection process and a 72-hour high-temperature aging test before shipment, and is backed by a one-year warranty from the date of sale. Standard delivery includes the sensor, a 5 m shielded cable, an instruction manual and a certificate of conformity.

Planning an ammonium monitoring project? Send us your requirements — our engineers will return a configuration proposal, wiring diagram and quotation within one business day.