SX731 portable pH/ORP/Conductivity (EC)/TDS/Salinity/Resistivity Meter


Plus 19% MwSt. DE

The SX731 from Apera Instruments is designed to measure pH, ORP, conductivity (EC), TDS, salinity and resistivity in laboratory quality and is suitable for all general water solutions. The SX731’s handy design as well as its dust and water resistance (IP57) and the rugged carrying case included in the scope of delivery make it ideal for field use, even in harsh environments. The integrated memory function allows 300 data sets to be stored and recalled. Possible applications include water treatment, environmental monitoring, beverage production, aquaculture, groundwater, surface water and aquarium monitoring, etc.

The 201T-S pH/Temp. electrode included in the set enables fast and precise pH measurements due to its lithium glass membrane and ceramic diaphragm. The 2301T-S conductivity/temp. electrode is based on our unique BPB (Brush-resistant Platinum Black) electrode technology and is characterized by its precision and wide measuring range (0-200 mS/cm). Both electrodes can additionally measure temperature through an integrated thermistor and perform automatic temperature compensation when measuring pH or conductivity. For accurate and reliable ORP determination, the 301Pt-S ORP electrode is supplied, which is equipped with a high quality platinum sensor. It does not need to be calibrated and is easy to clean.

  • Equipped with the 201T-S pH electrode, the 301Pt-S ORP electrode and the 2301T-S conductivity/temp. electrode
  • Precise, fast and reliable measurement of pH, redox potential (ORP), conductivity (EC), TDS, salinity, resistivity and temperature
  • Easy change between conductivity, TDS, salinity and resistivity
  • Quick & easy 1 to 3 point pH calibration and 1 point EC calibration
  • A special digital filter technology additionally improves response time and measurement accuracy
  • The integrated memory function allows the storage and retrieval of 300 data sets
  • Dust and water protected according to IP57, ideal for use in harsh environments
  • Supplied as a complete test kit in a robust carrying case

The Apera Instruments SX731 has a 3-year manufacturer’s warranty (6 months for electrodes).

Technical Specifications

pH value Measuring range (-2.00 to 19.99) pH
Resolution 0.1/0.01 pH
Accuracy Instrument: ±0.01 pH; Total: ±0.02 pH
Input current ≤2×10-12 A
Input impedance ≥1×1012Ω
Stability ±0.01 pH/3h
Temp. compensation (0 to 100) °C (automatic)
Redox potential (ORP) Measuring range (mV/ORP/EH) -1999mV to 0 to 1999mV
Resolution 1 mV
Accuracy Device: ±0.1% FS, Total: ±15 mV
Conductivity (EC) Measuring range Conductivity:

(0.00 to 19.99) μS/cm, (20.0 to 199.9) μS/cm

(200 to 1999) μS/cm, (2.00 to 19.99) mS/cm

(20.0 to 199.9) mS/cm

TDS: (0 to 100) g/L;

Salinity: (0 to 100) ppt

Resistivity: (0 to 100) MΩ·cm

Resolution 0.01/0.1/1 μS/cm; 0.01/0.1 mS/cm
Accuracy Device: ±1.0 F.S, Total: ±1.5% F.S
Temp. compensation (0 to 50) °C (automatic)
Electrode constant 0.1 / 1 / 10 cm-1
Reference temperature 25°C, 20°C, and 18°C
More Data storage 300 data sets
Data content Serial number, measured value, measuring unit and temperature
Power supply 2 AA batteries (1.5V x2)
Dimensions and weight Meter: (65×120×31) mm/180 g

Complete set: (255×210×50) mm/1490 g

Quality and safety certification CE, ISO 9001:2015
IP rating IP57

scope of delivery

A complete set contains:

  • SX731 pH/ORP/conductivity meter
  • 201T-S pH/temp. electrode
  • 301Pt-S ORP electrode
  • 2301T-S conductivity/temp. electrode
  • pH 4.00 Calibration solution, 50 ml
  • pH 7.00 Calibration solution, 50 ml
  • pH 10.01 Calibration solution, 50 ml
  • 1413 μS Conductivity calibration solution
  • manual
  • 2x AA battery
  • Screwdriver
  • Carrying case


German SX731 DE
English SX731 EN