Professional Plus (Pro Plus) Multiparameter Instrument

Multiparameter Instrument for DO, Conductivity, Salinity, pH, ORP, Ammonium, Nitrate, Chloride, Temperature and more. Meter Only

The Pro Plus multiparameter meter provides extreme flexibility for the measurement of a variety of combinations for dissolved oxygen, conductivity, specific conductance, salinity, resistivity, total dissolved solids (TDS), pH, ORP, pH/ORP combination, ammonium (ammonia), nitrate, chloride and temperature. Also a very powerful lab instrument for BODs, pH and ORP.

EPA approved for drinking water and wastewater compliance reporting.


The Quatro cable attached to the Pro Plus allows you to utilize 4-ports to measure temperature/conductivity, DO, and any two ISEs among pH, ORP, ammonium, chloride, or nitrate creating an extremely powerful handheld multiparameter instrument.

The Pro Plus instrument meets the demands of true field work. The instrument is rated to IP-67 standards even without the battery cover on. Other tough features include a 3-year warranty, Mil-spec connectors, rubber overmolded case, and a 2-year cable warranty. In-house testing procedures also include 1-meter drop tests from all angles to ensure expected field-durability.

Tough, Field Durability Features Include:

  • Easy-to-install cable weights; can be daisy-chained for additional weight*
  • Rubber, over-molded IP-67 waterproof case (even without the battery cover)*
  • 3-year instrument warranty
  • 2-year cable warranty*
  • Rugged cables, sensors, and military-spec connectors*
  • Drop-tested 1 meter at all angles*
  • Scratch-resistant lens; viewable with polarized glasses
  • Instrument floats
  • Weighted, user-replaceable multi-sensor design

The instrument provides numerous benefits from the following features; 5,000 data-set memory, password protection, backlit display and keypad, graphic display with detailed Help functionality, re-cal prompts, user defined fields, detailed GLP, auto stable, Hold All Readings function, Data Manager software for the desktop, USB connection, auto-buffer recognition, and flexible folders and site lists for logging data.

Smart Features Include:

  • 5,000 data set memory
  • Detailed on-screen Help function*
  • Free, Data Manager desktop software and ProComm II saddle*
  • Interval or single-event logging
  • 100 folder & site list data structure*
  • Password protection
  • Detailed GLP data
  • USB connection also powers the instrument
  • 6-point cal with auto-buffer recognition*
  • User-adjustable auto-stable with prompts*
  • User-upgradeable software via waterproof USB port
  • Recalibration prompts
  • Search function filters user-defined data information*
  • Backlit display AND keypad*
  • Cable management kit included with all cables from 4- to 30-meters*

Most Versatile
Connect any Professional Series cable (excludes ODO cables) and probe option to the instrument and use the convenient cable management kit to keep everything simple and organized. Cable options range from 1-, 4-, 10-, 20-, and 30-meter choices (up to 100-meters on DO only cables). Use lab or field probes and switch between the two quickly. The Pro Plus makes an ideal lab BOD instrument with the proven self-stirring BOD probe (EPA Approved). A convenient handstrap can be used on either side of the instrument. A complete family of accessories also increases the versatility of the Pro Plus. Choose among accessories including carrying cases, flow cells, cable weight, belt clip, tripod, and c-clamp.

YSI now offers an Extended Warranty for the Pro Plus (new instruments only).

Please visit the Professional Plus Kits page for fully assembled systems.

Added Versatility Features Include:

  • Adjustable right- or left-handed hand strap*
  • Multiple user-replaceable sensor options and a choice of DO sensors*
  • Multiple parameter options and cable lengths
  • Lab-grade ISE sensors and BOD probe available to make a true lab/field instrument
  • Languages – English, Spanish, German, French, Italian, Norwegian, Portuguese, Japanese, Chinese (Simplified and Traditional)
  • Wide array of accessories are available from flow cells, to shoulder straps, to carrying cases

Free – Data Manager – Watch the Data Manager Demo Video
Data management can become a daunting task over time but with the Data Manager software this task is much simpler and efficient. Download data, configure instruments, and conduct real-time studies easily with Data Manager software. View data graphically or in tabular form and export data as needed to other programs. Data Manager software is a very powerful tool. So powerful in fact, that we give it to you at no charge when purchasing a Pro Plus. After all, it’s all about the data!

When purchasing the Pro Plus you will receive the instrument, manual, batteries, communications saddle, USB cable, and Data Manager software. Cables and probes are ordered separately.

Autostable User-defined auto-stable function holds stable readings on display when criteria is met
Certifications RoHS, CE, WEEE, C-Tick, VCCI, FCC, IP-67 (waterproof), 1-meter drop test, Assembled in USA
Connectivity / Communications USB 2.0 for data transfer and user-upgradeable instrument firmware. Communications saddle, USB cable and Data Manager software included
Connector Metal MS (military spec) waterproof with bayonet lock
Data Management 5000 data set memory in Pro Plus with 100 user-defined sites and site names. Data Manager desktop software included
Desktop Software Compatible Data Manager desktop software included. Minimum PC requirements – Windows 2000 with SP4 (minimum) or XP with SP2 (minimum), Vista 7 or Windows 8 | 300 MHz or higher Pentium-compatible CPU | 128 MB of RAM or higher | 80 MB or more of free hard-disk space
Digital / Digital Sensors No, the Pro Plus is an analog instrument
GLP Compliance Yes, detailed GLP information is stored and is available to view, download or print
Graphic Display Graphic display can be seen in any lighting condition and with polarized glasses | Backlit display AND keypad | Includes detailed on-board Help
Languages English, Chinese (Simplified and Traditional), Italian, Japanese, French, German, Portuguese, Spanish, Norwegian
Logging Capabilities Single or Continuous
Memory 100 GLP files, 5,000 data sets (data, date, time, user-defined info)
Multiparameter Yes
Operating Temperature -10 to 60°C
Parameters Measured Temperature, Dissolved Oxygen, pH, ORP/Redox, Conductivity, TDS, Ammonia, Ammonium, Nitrate, Chloride,Built-in barometer
Power ProComm II saddle provides USB power or optional wall power, cigarette lighter, and universal cell phone charger options, 2 alkaline C-cells provide 80 continuous hours at ambient temperature without backlight
Sampling Yes
Storage Temperature -20 to 70°C
Unit of Measure Conductivity-mS/cm, Barameter-mmHg, pH-units, Chloride-mg/L, Salinity-ppt, ORP-mV, Temperature- °C, mg/L, air saturation, Nitrate-mg/L-N, Dissolved Oxygen-%, Total Dissolved Solids(TDS)-g/L, Ammonium-mg/L-N, °F
User Calibratable Yes
User Replaceable Yes, cables and most sensors are user-replaceable
Warranty 3-year instrument; 2-year field cables
Waterproof IP-67 (even with the battery cover off and cable disconnected), floats

Professional Plus Instrument General Specifications

Barometer Built-in barometer
Buffer Recognition Auto buffer recognition for US and NIST buffers
Cables: Field Standard lengths of 1, 4, 10, 20, or 30 meters – up to 100 meters on DO only cables;  4- through 30-meter cables include a cable management kit
Cables: Lab BOD sensor includes 2-meter cable; 1 or 4 meters on lab pH, ORP and pH/ORP cables
Dimensions 8.3 cm width x 21.6 cm length x 5.6 cm depth (3.25 in x 8.5 in x 2.21 in)
DO Membrane Response Times (T95; 100%-0) and Required Flow Rate 1.25 mil PE = 8 seconds and 6 in/sec flow
2.0 mil PE = 17 seconds and 3 in/sec flow
1 mil Teflon® = 18 seconds and 12 in/sec flow
DO Sensors Polarographic or galvanic field sensors; self-stirring polarographic BOD sensor for the lab
Flow Cell Single, dual and multiparameter Quatro cable all flow cell compatible
User ID Optional user ID for data security
Weight 475 grams (1.05 lbs)


Professional Plus System Specifications (Instrument, Cables & Sensors)

Sensor Type Range Accuracy Resolution Calibration
(mg/L-N mV)
ammonia with pH sensor
Ion Selective Electrode 0 to 200 mg/L-N, 0 to 30°C ±10% of reading or 2 mg/L-N, whichever is greater 0.01 mg/L 1, 2, or 3 point
(user selectable)
(mmHg, inHg, mbar, psi, kPa, ATM)
Piezoresistive 375 to 825 mmHg ±1.5 mmHg from 0 to 50°C 0.1 mmHg 1 point
(mg/L-Cl-, mV)
Ion Selective Electrode 0 to 1000 mg/L, 0 to 40°C​ ±15% of reading or 5 mg/L, whichever is greater 0.01 mg/L 1, 2, or 3 point
(user selectable)
(µS, mS)
Four Electrode Cell 0 to 200 mS/cm (auto-range) 1 m, 4 m cables:
±0.5% of reading or 0.001 mS/cm, whichever is greater
20 m cable:
±1% of reading or 0.001 mS/cm, whichever is greater
Range dependent

0 to 0.500 mS/cm: 0.001
0.501 to 50.00 mS/cm: 0.01
50.01 to 200 mS/cm: 0.1


1 point
Dissolved Oxygen
(% saturation)
temp comp range -5 to 50°C
Polarographic or Galvanic 0 to 500% 0 to 200% :
± 2% of reading or 2% air saturation, whichever is greater
200% – 500% :
± 6% of reading
0.1% or 1% air saturation (user selectable) 1 or 2-points with zero
Dissolved Oxygen
(mg/L, ppm)
temp comp range -5 to 50°C
Polarographic or Galvanic 0 to 50 mg/L 0 to 20 mg/L :
± 2% of reading or 0.2 mg/L, whichever is greater
20 – 50 mg/L :
± 6% of reading
0.1 or 0.01 mg/L (user selectable); 0.1% air saturation 1 or 2-points with zero
(mg/L-N mV)
Ion Selective Electrode 0 to 200 mg/L-N, 0 to 30°C ±10% of reading or 2 mg/L-N, whichever is greater 0.01 mg/L 1, 2, or 3 point
(user selectable)
Platinum Button -1999 to +1999 mV ±20 mV in redox standards 0.1 mV 1 point
(mV, pH units)
Glass Combination Electrode 0 to 14 units ±0.2 units 0.01 units 1, 2, 3, 4, 5, or 6 point (user selectable); US, NIST or Custom Buffers
(ppt, PSU)
Calculated from Conductivity and Temperature 0 to 70 ppt ±1.0% of reading or ±0.1 ppt, whichever is greater 0.01 ppt 1 point
Field-rugged cables
(°C, °F, K)
Thermistor -5 to 70°C (23 to 158°F) ±0.2°C;
±0.3°C cables over 45-meters
0.1°C None
Lab-grade cables​
(°C, °F, K)
Thermistor 0 to 40°C (32 to 104°F) ±0.35°C 0.1°C None
Total Dissolved Solids (TDS)
(mg/L, kg/L, g/L)
Calculated from Conductivity and Temperature 0 to 100 g/L; TDS constant range 0.30 to 1.00 (0.65 default) 0.001, 0.01, 0.1g/L

Aquaculture Applications Parameters & Capabilities


Water Monitoring Solutions


Water Monitoring Solutions | E58-07 Municipal Water Catalog


Water Quality Sampling


YSI Professional Series Built Tough Brochure


YSI Professional Plus Water Quality Meter Specifications W14-04


YSI Model 556 Quick-Start Guide


YSI Pro Plus User Manual


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