SX751 portable pH/Dissolved Oxygen (DO)/ORP/Conductivity (EC)/TDS/Salinity/Resistivity Meter


Plus 19% MwSt. DE

The SX751 from Apera Instruments is designed for laboratory-quality measurement of pH, dissolved oxygen (DO), redox potential (ORP), conductivity (EC), TDS, salinity and resistivity and is suitable for all general water solutions. The SX751’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 400 data sets to be stored and retrieved. 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 oxygen measurements the polarographic DO500 electrode is supplied, which is polarized and ready for measurement after only 5 minutes. Due to its mode of operation, automatic temperature and salinity compensation as well as manual air pressure compensation, the electrode allows fast and precise DO measurements. For accurate and reliable ORP determination, the 301Pt-S ORP electrode is included, which is equipped with a high quality platinum sensor. It does not require calibration and is easy to clean.

  • Equipped with the 201T-S pH electrode, the 301Pt-S ORP electrode, the 2301T-S conductivity/temp. electrode and the DO500 polarographic electrode.
  • Precise, fast and reliable measurement of H-value, dissolved oxygen (DO), 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
  • Replaceable DO membrane cap (3 replacement membrane caps and a matching refill solution are included in the kit).
  • Electrode polarization takes only 5 minutes. The oxygen measurement reaches a response of 90% within 30 seconds
  • A special digital filter technology additionally improves response time and measurement accuracy
  • The integrated memory function allows the storage and retrieval of 400 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 SX751 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
Dissolved Oxygen (DO) Measuring range (0 to 19.99) mg/L (ppm); (0 to 200.0) %.
Resolution 0.1/0.01 mg/L (ppm); 1/0.1 %
Accuracy ±0.30 mg/L (ppm), incl. Electrode error
Response time ≤ 30s (90% response at 25°C)
Temp. compensation (0 to 45) °C (automatic)
Salinity compensation (0 to 45) ppt (automatic)
Air pressure compensation (66 to 200) kPa (manual)
Automatic calibration Air saturated with water; water saturated with air
Electrode type Polarographic
More Data storage 400 data sets
Memory values 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/1760 g

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

scope of delivery

A complete set contains:

  • SX751 pH/oxygen (DO)/ORP/conductivity (EC)/TDS/salinity/resistivity meter
  • 201T-S pH/temp. electrode
  • 301Pt-S ORP electrode
  • 2301T-S conductivity/temp. electrode
  • DO500 polarographic DO 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
  • DO502 electrolyte solution for refilling
  • 3x DO503 membrane cap
  • Polishing paper for cleaning the electrode
  • manual
  • 2x AA battery
  • Screwdriver
  • Carrying case


German SX751 DE
English SX751 EN