
   SPECIFICATIONS 
   DOCUMENT #W55
YSI Pro20i Dissolved Oxygen/Temperature
Portable Dissolved Oxygen Meter for the Field
Easy to use, rugged and reliable, the YSI Pro20i provides 
everything you need in a handheld instrument for the 
measurement of dissolved oxygen (DO). A true field instrument 
with IP-67 waterproof, rubber over molded case, military spec 
connectors and 1-meter drop tests ensure durability to provide 
years of sampling even in the harshest field conditions.
With the Pro20i, accuracy is not compromised for ruggedness. 
The Pro20i can easily be calibrated for fast, accurate 
measurements you can trust. 
• Integral (i.e. built-in) cable with 1- 4- 10-m field cable
Parameters:
Dissolved Oxygen 
  (DO%, DO% Local, ppm and mg/L)
Temperature  
   (°C, °F) 
Barometric Pressure 
   (mmHg, inHg, mbar, psi, kPa)
• User-replaceable DO sensors 
• One Touch Cal allows for easy DO calibrations within 3 seconds 
with the press of a button 
• Automatic barometric pressure compensation 
• Quick response times; T-95 response time in 8 seconds with 
standard membrane (fastest response time on the market)
• Stores 50 data sets; no need to write down data
• Large graphic, backlit display and glow in the dark keypad, 
visible in any lighting condition
• Display is visible when wearing polarized sunglasses
• A true field instrument with IP-67, impact-resistant, waterproof 
case. Waterproof with and without the battery cover. 
• Rubber over molded, slip-proof case provides extra durability 
• Multiple languages: English, Spanish, French, and German
• Warranty: 3-year instrument, 2-year integral cable, 1-year 
polarographic sensors, 6-month galvanic sensor 
YSI.com/pro20i

Pro20i System Specifications (Instrument, Probe, and Cable) 
Temperature   Range  23 to 131°F (-5 to 55°C) 0 to 45°C for DO compensation for mg/L
°C, °F Resolution 0.1°F (0.1°C) 
  Accuracy  ±0.6°F (±0.3°C) 
Dissolved Oxygen  Range  0 to 500%
% Saturation  Resolution  0.1% or 1% air saturation (user selectable) 
% Local Accuracy 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
Dissolved Oxygen  Range  0 to 50 mg/L
mg/L  Resolution  0.01 or 0.1 mg/L (user selectable) 
ppm Accuracy 0 to 20 mg/L, ±2% of the reading or ±0.2 mg/L, whichever is greater; 
     20 to 50 mg/L, ±6% of the reading
Barometer   Range  400 to 999.9 mmHg
mmHg, mbar, inHg,  Resolution  0.1 mmHg 
psi, kPa Accuracy ±5 mmHg within ±5°C temperature range from calibration point
Pro20i Additional Specifications
Size 8.3 cm width x 21.6 cm length x 5.6 cm depth (3.25 in. x 8.5 in. x 2.2 in.) 
Weight with Batteries    475 grams (1.05 lbs.) 
Power 2 alkaline C-cells providing ~400 hours of battery life (without backlight); low battery indicator when 1 hour is left 
Cables 1- 4- 10-m lengths (3.28, 13.1, 32.8 ft.) 
Warranty 3-year instrument; 2-year cable; 1-year polarographic sensors; 6-month galvanic sensors 
Salinity Input Range    0-70 ppt; manual (automatically compensates for manual input value) 
Data Memory    50 data sets 
Languages    English, Spanish, German, French 
Certifications    RoHS, CE, WEEE, IP-67 waterproof, 1-meter drop test 
Country of Origin    Instrument Assembled in the USA, cable and probe Made in the USA
Pro20i Ordering Information - Full range of accessories available at YSI.com/pro20i
607130 Pro20i-1 P Kit  Dissolved Oxygen and Temperature handheld instrument with 1-meter integral cable and 2003 polarographic sensor kit 
607131 Pro20i-1 G Kit  Dissolved Oxygen and Temperature handheld instrument with 1-meter integral cable and 2002 galvanic sensor kit 
607125 Pro20i-4 P Kit  Dissolved Oxygen and Temperature handheld instrument with 4-meter integral cable and 2003 polarographic sensor kit 
607129 Pro20i-4 G Kit  Dissolved Oxygen and Temperature handheld instrument with 4-meter integral cable and 2002 galvanic sensor kit 
607132 Pro20i-10 P Kit  Dissolved Oxygen and Temperature handheld instrument with 10-meter integral cable and 2003 polarographic sensor kit 
607133 Pro20i-10 G Kit  Dissolved Oxygen and Temperature handheld instrument with 10-meter integral cable and 2002 galvanic sensor kit 
605202    Galvanic Dissolved Oxygen sensor; 5913 (yellow cap) membrane kit included   
605203    Polarographic Dissolved Oxygen sensor; 5908 (yellow cap) membrane kit included 
YSI
1725 Brannum Lane, Yellow Springs, OH 45387 
Tel +1 937.767.7241  800.897.4151 (US) 
info@ysi.com 
@YSIinc 
YSI.com
YSI is a registered trademark.          
Specifications are subject to change. Please visit YSI.com to verify all specs. 
©2016 YSI, a xylem brand 
   Printed in the USA. W55 November, 2016