Orion Star™ A121 pH Portable Meter

Advanced Sensors

General Details

Take simple, routine pH, mV and temperature measurements with the Thermo Scientific™ Orion™ Star A121 pH Portable Meter, an easy-to-use and budget-friendly instrument for basic pH analysis in the field. Perform up to a three point pH calibration with easy recall of calibration points and slope. Quickly navigate setup menus and ensure consistent calibrations using the simple keypad layout and on-screen text prompts. This waterproof meter has an IP67-rated housing for rugged protection in outdoor environments.



Orion Star A121 pH portable meter


Orion Star A121 pH/mV/RmV/Temperature Portable Meter

Item Description

Orion Star A121 pH portable meter


Star A121 pH meter, 4 AA batteries, literature CD, printed quick start guide and meter test certificate

Range (pH)

2.00 to 16.00pH

Resolution (pH)

0.1, 0.01pH

Accuracy (pH)


Range (mV)


Range (Relative mV)


Resolution (mV)


Accuracy (mV)

±0.2 mV or ±0.05% of reading whichever is greater


pH, relative mV (RmV) and temperature

Calibration Points (pH)

1 to 3

Calibration Points

1 point relative mV (RmV) mode

Isopotential Point


Range (Temperature)

5.0° to 105.0° C, 22.0° to 221.0° F

Resolution (Temperature)

0.1°C, 0.1°F

Accuracy (Temperature)


Temperature Selection

Manual or automatic with ATC temperature probe

Temperature Probe Calibration

1 point temperature offset calibration



Display Type



Simple with highlighted measure key, scroll and shortcut keys

Measurement Modes

pH, mV or relative mV (RmV) with temperature


Smart Stability and Smart Averaging

Data Management Details

Internal data point memory

Data Points 50
Log Function Type Automatic data logging with Auto­Read measure mode; manual data logging with Continuous measure mode

Non­volatile memory preserves log and settings

Languages English

BNC (pH or ORP electrode), 8 pin MiniDIN (ATC temperature probe)

Outputs None
Probe Type pH electrode, ORP electrode, ATC temperature probe (purchase separately)
Power Supply 4 AA batteries (included) or universal AC adapter (sold separately)
AC Adapter

Universal 50­60 Hz, 100­240 VAC power adapter (sold separately, Cat. No. 1010003)

Battery Life

2000 hours
Battery Type Four AA (included)
IP Rating IP­67
Certifications/Compliance Certifications/Compliance

Temperature (English) Operating

41° to 113°F (ambient)

Temperature (Metric) Operating 5° to 45° C (ambient)
Relative Humidity Range 5 to 85 %, non­condensing
Dimensions (L x W x H) 24cm x 10cm x 6.5cm (9.5 in. x 3.9 in. x 2.6 in.)
Weight (English) 2 lb.
Weight (Metric) 0.5kg
Warranty 3 year meter warranty
Thermo Scientific Orion Star A121 pH portable meters are a simple, economical solution for your routine outdoor sample analysis. Featuring an emphasized measure key, selectable read modes and measurement stability indicator, our basic Orion Star A121 pH meters are designed to deliver measurements you can trust at an affordable price.
  • Measure pH, mV or relative mV with temperature
  • Perform up to a three point pH calibration with automatic buffer recognition or manual buffer entry
  • Simplified, easy-to-read display shows main measurement with temperature, stability indicator and electrode condition icon
  • User-friendly operation with basic calibration text prompts
  • Easily recall calibration data for procedure checks
  • Non-volatile memory preserves 50 point internal data log and meter settings, even with loss of power
  • Flexible power options with AA batteries or optional universal power adapter
  • IP67-rated housing is waterproof for rugged field operation
  • Meter kits include hard-sided field case and protective meter armor with electrode holders, adjustable wrist/belt strap and built-in meter stand
  • Meters offer CE, TUV 3-in-1 and FCC Class A certifications and 3-year replacement warranty