SX725 portable pH/Dissolved Oxygen (DO) Meter


Plus 19% MwSt. DE

The SX725 from Apera Instruments is designed for laboratory quality pH and dissolved oxygen (DO) measurement and is suitable for all general water solutions. The SX725’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. Due to the integrated thermistor, temperature is additionally measured and an automatic temperature compensation is performed during pH measurement. 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, the automatic temperature and salinity compensation as well as the manual air pressure compensation, the electrode enables fast and precise DO measurements.

  • Equipped with the 201T-S pH/temp. electrode and the DO500 polarographic electrode
  • Precise, fast and reliable measurement of pH, Dissolved Oxygen (DO) and temperature
  • 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 90% response within 30 seconds.
  • Quick and easy 1 to 3 point pH 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 SX725 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)
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 300 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/1380 g

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

scope of delivery

A complete set contains:

  • SX725 pH/dissolved oxygen (DO) meter
  • 201T-S pH/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
  • DO502 electrolyte solution for refilling
  • 3x DO503 membrane cap
  • Polishing paper for cleaning the electrode
  • manual
  • 2x AA battery
  • Screwdriver
  • Carrying case


German SX725 DE
English SX725 EN