Ensure accurate and reliable measurements in your laboratory and research locations

Our benchtop pH and ORP (Oxidation-Reduction Potential) meters are designed to address a variety of measurement requirements for dependable performance, accuracy, and reproducibility. Identify the best match based on your required features, performance specifications, and budget.

Which benchtop pH and ORP meter is right for you?





 Orion Versa Star Pro pH
Benchtop Meter

(VSTAR10 series)
Orion Star 
A211 pH
Benchtop Meter

(STARA211 series)
Orion Star 
A111 pH
Benchtop Meter

(STARA111 series)
 Premium pH and ORP benchtop metersAdvanced pH and ORP benchtop metersBasic pH and ORP benchtop meters
 Versatile, high-performance laboratory measurement systemEasy to use, dependable laboratory metersEconomical, simplified
laboratory meters
Ideal for
applications in: 
Pharmaceuticals, biotechnology, food and beverage, industrialWater, 
chemical contract testing
pH range–2.000 to 20.000–2.000 to 20.000 –2.00 to 16.00
pH resolution0.001 / 0.01 / 0.10.001 / 0.01 / 0.10.01 / 0.1 
pH calibration pointsUp to 6Up to 5Up to 3 
pH calibration modesAuto buffer recognition with option to edit valuesAuto buffer recognition with option to edit valuesAuto buffer recognition or manual buffer entry 
Automatic buffer setsUSA/NIST, DIN or customUSA/NIST or DINUSA/NIST or DIN
mV, RmV modesYes YesYes
ORP modeYes Yes
Display typeAdjustable color graphic LCDGraphic LCDFixed segment LCD
Backlit displayYesYes
Onscreen text promptsStep-by-step calibration and guided setup instructionsStep-by-step calibration and guided setup instructionsBasic calibration and setup prompts
KeypadNumeric with menu-specific function keysComprehensive with menu-specific function keysSimple with highlighted measure key
Number of channels4, customizable with modules11
Included modules1 x VSTAR-PH
Stirrer probe inputs21
Measure read modesAuto-read, continuous, timed, single-shotAuto-read, continuous, timedAuto-read, continuous
Methods10 per channel10
Data log2000 with date/time2000 with date/time50
Calibration log30 per mode10
Identification optionsElectrode ID, sample ID, user IDSample ID, user ID
AlarmsSet point, high/low limit, calibration dueHigh/low limit, calibration due
External device outputUSB(2), RS232USB, RS232
CertificationsIP-54, CE, TUV 3-in-1, FCC Class AIP-54, CE, TUV 3-in-1, FCC Class AIP-54, CE, TUV 3-in-1, FCC Class A
Power supplyUniversal, 100–240 VAC, 50-60 Hz Cat. No. STARA-PWR)Universal, 100–240 VAC, 50–60 Hz (Cat. No. 1010003) or 4 AA batteriesUniversal, 100–240 VAC, 50–60 Hz (Cat. No. 1010003) or 4 AA batteries
  Increase your productivity by adding accessories to your benchtop or portable meter. Meter Accessories ›

Confidence in your pH measurements

The accuracy and reliability of your measurements depend on the instrumentation you use. Learn more about the other products offered as part of this portfolio.

pH and ORP Meters

pH and ORP portable meters

Are you taking samples in the field and bringing them back to the lab? Our portable pH meters are designed to offer simple and accurate pH measurements for your on-the-go measurements. Find the ideal portable meter to complement your laboratory application. 


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pH Electrodes
and Probes

pH and ORP electrodes and probes

Our extensive assortment of quality pH electrodes, sensors, and probes are designed to make your complex measurements routine, reliable, and accurate—in the lab or in the field. They are available in a variety of body materials, body styles, and sample requirements. Find the best electrode for your application.


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Buffers and

buffers and solutions

We offer a variety of pH buffer solutions, pH electrode storage solutions, electrode cleaning solutions, lab buffer kits, and electrode filling solutions for every application. All Thermo Scientific Orion pH lab buffers and solutions are traceable to NIST reference materials. Find the buffers and solutions necessary to complete your measurements.

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Featured pH measurement videos

Calibrating a Thermo Scientific Orion Star A series pH benchtop meter

Measuring pH in drinking water using the Thermo Scientific Orion Versa Star Pro benchtop meter


Knowledge Base: Certificates of Analysis and SDS for Orion, ROSS, AQUAfast, AquaMate, and AquaSensors products.

Orion Meters Software and Upgrades
Thermo Scientific Orion benchtop and portable meters are designed to help deliver accurate, consistent results, day after day. Boost productivity by upgrading your software today.

Find your software