YEX-S2-PH-S Industrial Online pH Sensor | RS485/4-20mA

YEX-S2-PH-S is a flagship-series industrial online pH sensor with a dual-interface design (RS-485 Modbus RTU + 4–20 mA), built for projects that must serve both digital SCADA/PLC networks and legacy analog control loops without maintaining two different probes. It continuously measures pH and temperature with automatic temperature compensation in wastewater treatment, aquaculture, process water and chemical dosing applications.

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.

For engineering contractors and OEM panel builders, the S2 series answers one recurring specification problem: many plants mix modern Modbus RTU data loggers with older 4–20 mA analog cards. The S2-PH-S is engineered to integrate into both worlds from a single probe, which simplifies cabinet design, spares management and future control-system upgrades.

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.

• Industrial pH measurement: 0.00–14.00 pH range with 0.01 pH resolution and automatic temperature compensation for stable readings across seasonal temperature swings.

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

• 12–24 V DC operation: compatible with solar-powered monitoring stations and standard control-cabinet supplies.

Application Scenarios

1. Wastewater treatment: inlet load tracking, aeration basin pH control and discharge compliance monitoring with continuous records for SCADA.

2. Chemical dosing control: closed-loop acid/alkali dosing where the 4–20 mA signal feeds existing PID controllers while Modbus data streams to a plant historian.

3. Aquaculture and RAS: pond and recirculating-system pH monitoring combined with DO and ammonium sensors on the same bus.

4. Process water and cooling loops: corrosion-tendency monitoring with alarm logic and trend records for maintenance planning.

Technical Specifications

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

Engineering Selection and Integration Notes

Installation position

Install the probe at a representative, continuously wetted and well-mixed point. Avoid dead zones, direct chemical-injection impact, sediment accumulation and locations where bubbles collect. Do not install the glass electrode upside-down or horizontally — keep the installation angle at least 15° from horizontal so the electrode bulb stays properly wetted and air bubbles cannot lodge inside it.

Electrical connection

Use the four-core shielded cable per the wiring diagram supplied with the sensor: power positive, power negative, RS-485 A, RS-485 B. Waterproof all junction points; add protective sleeving where the cable is exposed to sunlight or corrosive liquids. When the 4–20 mA interface is used, confirm the mapped full-scale value and loop burden with our engineers during commissioning.

Calibration routine

The sensor is calibrated before shipment, but commissioning verification and periodic two-point buffer calibration (typically pH 4.00/6.86/9.18 depending on your range) are required. Set the interval from drift data and fouling conditions — monthly checks are common in clean process water, while high-load wastewater may need shorter intervals.

Frequently Asked Questions

What makes the S2-PH-S different from the YEX-S1-PH?

Both sensors measure pH and temperature with RS-485 Modbus RTU output. The S2-PH-S belongs to the flagship tier and adds 4–20 mA output support in the same probe — designed for projects that run mixed digital/analog architectures or want upgrade headroom — with extended configuration freedom and OEM-level engineering support. If your project is a straightforward Modbus-only station, the S1-PH is the more cost-effective choice.

Can the RS-485 and 4–20 mA outputs work at the same time?

The S2 series is designed as a dual-interface product. 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 controller or PLC can the sensor connect to?

Any host supporting the standard Modbus RTU protocol (PLCs, RTUs, dataloggers, IoT gateways) can read the sensor over RS-485; the 4–20 mA interface connects to standard analog input cards. We provide the complete register map, default device address and baud rate with every order.

What information should I provide before requesting a quotation?

Provide the water matrix, expected pH range, normal operating temperature, installation method (immersion, flow cell or pipe insertion), cable distance, power supply, control-system interface (Modbus, 4–20 mA or both) and quantity. These inputs determine the configuration, accessories and integration scope.

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