Manufacturer: YSI
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Rugged, reliable and waterproof, the YSI 556 MPS (Multiprobe System) combines the versatility of an easy-to-use, easy-to-read handheld unit with all the functionality of a multiparameter system.

Featuring a waterproof IP-67, impact-resistant case, the YSI 556MPS simultaneously measures dissolved oxygen, pH, conductivity, temperature, and ORP. Or, simply purchase the cable to measure DO, conductivity, and temperature if needed. The YSI 556 MPS conforms to GLP standards.

Key Features

  • Powered by alkaline batteries or an optional rechargeable battery pack with fast charge feature
  • Internal barometer can be user-calibrated and displayed along with other data, used in dissolved oxygen calibrations, and logged to memory for tracking changes in barometric pressure
  • Comes standard with a soft-sided carrying case with enough space for the YSI 556 MPS, a 20-meter cable, and calibrating supplies
  • Field-replaceable DO, pH, and pH/ORP probes
  • RS-232 and compatible with EcowatchTM for WindowsTM data analysis software
  • Easy-to-use, screw-on cap DO membranes
  • User-upgradable software from YSI website
Pair the 556 up with the 5083 flow cell and hard side carrying case and you have a complete groundwater package. The 5083 flow cell is extremely simple to connect to the 556 and cleans up even easier.

In order to ensure data quality be sure to use the 5580 Confidence Solution with the 556 . Quickly check pH, ORP, and conductivity values to guarantee probe accuracy during important field studies.

The 556 also features menu-driven operation with multiple languages including Spanish, French, Italian, German, Norwegian, and English.

Data management is simple with EcoWatch™ desktop software for tabular and graphical data representations.


  • Optional


  • 4, 10, or 20 meters (13.1, 32.8, or 65.6 ft.)


  • RS-232 Serial


  • MS (military spec) waterproof with bayonet lock

Data Management

  • EcoWatch desktop software compatible

Data Memory

  • 49,000 data sets (data, date, time, user-defined info); interval or manual logging


  • 11.9 cm width x 22.9 cm length (4.7" x 9")


  • 49,000 data sets, date and time stamp, manual or logging, with user-selectable intervals


  • 4 alkaline C-cells
  • Optional rechargeable pack

Weight with Batteries

  • 916 grams (2.1 lbs)
Sensor Type
Range Accuracy Resolution
Dissolved Oxygen (%) Polarographic 0 to 500% air saturation 0 to 200% air saturation, ± 2% of the reading or ± 2% air saturation, whichever is greater; 200 to 500% air saturation, ± 6% of the reading 0.1% air saturation
Dissolved Oxygen (mg/L) Polarographic 0 to 50 mg/L 0 to 20 mg/L, ± 0.2 mg/L or ± 2% of reading, whichever is greater; 20 to 50 mg/L, ± 6% of the reading 0.01 mg/L
Temperature Thermistor -5 to 45°C ±0.15°C 0.1°C
Conductivity Four electrode cell 0 to 200 mS/cm ±0.5% of reading or 0.001 mS/cm, whichever is greater (4-m cable) ±1% of reading or 0.001 mS/cm, whichever is greater (20-m cable) 0.001 mS/cm to 0.1 mS/cm (range dependent)
(auto range)
Salinity Calculated from conductivity and temperature 0 to 70 ppt ±1.0% of reading or 0.1 ppt, whichever is greater 0.01 ppt
pH (optional) Glass Combination Electrode 0 to 14 units ±0.2 units 0.01 units
ORP (optional) Platinum button -1999 to +1999 mV ±20 mV 0.1 mV
Total Dissolved Solids (TDS) Calculated from conductivity and temperature 0 too 100 g/L   4 digits
Barometer (optional)   500 to 800 mmHg ±3 mmHg within ±10°C temperature range from calibration point 0.1 mmHg