SANXIN SX825 Portable pH / Dissolved Oxygen Water Quality Analyzer

Overview

The SANXIN SX825 Portable pH / Dissolved Oxygen Water Quality Analyzer is an electrochemical field instrument engineered for reliable, on-site monitoring of two critical water quality parameters—pH and dissolved oxygen—in environmental, industrial, and municipal applications. Based on potentiometric measurement for pH and Clark-type polarographic detection for dissolved oxygen, the SX825 delivers laboratory-grade precision in a rugged, handheld form factor. Its dual-sensor architecture supports simultaneous or rapid sequential measurements without cross-interference, making it suitable for routine surveillance of surface water, wastewater effluents, aquaculture systems, cooling towers, and boiler feedwater. The analyzer complies with fundamental metrological requirements outlined in ISO 7888 (pH determination in water) and ASTM D888 (dissolved oxygen in water), and its data structure adheres to Good Laboratory Practice (GLP) principles through mandatory time-stamped metadata logging.

Key Features

• Triple-parameter electrochemical sensing platform: integrated pH, DO, and temperature measurement in a single handheld unit.
• Automatic temperature compensation (ATC) for both pH and DO channels, with built-in NTC thermistors in each electrode.
• Intelligent calibration management: automatic recognition of 12 standard pH buffer solutions (including 4.00, 6.86, and 9.18 at 25 °C); support for 1–3 point pH calibration and custom buffer definition.
• Dedicated operational modes: pure water pH mode and ammonia-added pure water pH mode—optimized for power plant demineralized water monitoring per IAPWS guidelines.
• Polarographic DO electrode (model 1DO500) with replaceable membrane cap assembly; <3–5 min polarization time; includes integrated salinity and temperature sensors for real-time compensation.
• IP57-rated enclosure ensures dust resistance and immersion protection up to 1 m for 30 minutes—validated per IEC 60529—enabling use in rain, high-humidity environments, or near splash zones.
• Ergonomic foldable stand and shock-absorbing carrying case (480 × 360 × 95 mm) with molded compartments for electrodes, buffers, and accessories.

Sample Compatibility & Compliance

The SX825 is validated for aqueous matrices including freshwater, seawater (with salinity compensation), wastewater, and low-conductivity purified water. It accommodates variable sample viscosities and suspended solids within typical environmental sampling constraints. All measurements meet traceability requirements under ISO/IEC 17025 when used with certified reference materials (e.g., NIST-traceable pH standards and Winkler titration-verified DO standards). The instrument’s firmware enforces GLP-compliant data handling—including immutable timestamps, operator ID fields (via optional configuration), and audit-ready storage logs—supporting regulatory readiness for EPA Method 150.1 (pH) and EPA Method 360.1 (DO). While not FDA 21 CFR Part 11-certified out-of-the-box, its USB-exported CSV files are compatible with validated LIMS environments requiring electronic record integrity.

Software & Data Management

Data acquisition and reporting are supported via PC-Link communication software (included on optical disc), enabling bidirectional transfer of all 1000 stored GLP records—including measurement value, unit, temperature, date/time stamp, and electrode status flags. Records are exported in comma-separated values (CSV) format with UTF-8 encoding for compatibility with Excel, LabArchives, and ELN platforms. Two storage modes are available: manual trigger and programmable auto-interval logging (1–999 minute intervals). Internal memory retains full datasets during battery replacement or unexpected power loss, satisfying IEC 62304 Class B software safety requirements for data persistence. No cloud connectivity or remote firmware updates are implemented—ensuring data sovereignty and network isolation in secure facilities.

Applications

• Field-based compliance monitoring for NPDES and Clean Water Act reporting.
• Process control in municipal drinking water treatment plants (coagulation, disinfection, filtration stages).
• Aquaculture health assessment—tracking diurnal DO fluctuations and pH stability in recirculating aquaculture systems (RAS).
• Industrial boiler and steam cycle chemistry programs—monitoring condensate pH and oxygen scavenger efficiency.
• Educational laboratories conducting AP Environmental Science or undergraduate limnology field modules.
• Emergency response teams assessing post-spill or post-flooding water quality in situ.

FAQ

Does the SX825 support calibration verification against secondary standards?
Yes—the instrument stores calibration history (date, buffer IDs, slope/mV offset, and asymmetry potential) for retrospective review. Users may manually compare fresh calibrations against archived reference values to assess electrode drift.
Can the DO electrode be used in high-turbidity or biofouling-prone waters?
The 1DO500 electrode features a Teflon-coated cathode and replaceable polyethylene membrane cap. Routine cleaning with mild detergent and periodic membrane replacement (using included spare caps) maintains accuracy in turbid or organically rich samples.
Is temperature compensation applied automatically during DO measurement?
Yes—temperature compensation is continuous and automatic across 0–45 °C. The built-in thermistor eliminates need for external probes or manual entry.
What happens if barometric pressure changes significantly during field use?
Users must manually input local atmospheric pressure (60.0–199.9 kPa) prior to DO measurement; the instrument applies this value to correct saturation percentage calculations per ISO 5814.
Are electrode diagnostics accessible without connecting to a PC?
Yes—on-device self-diagnostics display electrode impedance, polarization status, and membrane integrity warnings directly on the LCD during startup and calibration.