Thermo Orion Star A221 Portable pH Meter

The Thermo Orion Star A221 portable pH meter allows accurate pH data to be recorded in any setting.


  • Displays pH, mV, RmV and temperature readings using Orion waterproof BNC electrodes
  • AUTO-READ function alerts user and locks stable readings on backlit LCD screen
  • USB and RS-232 ports allow easy data transfer of up to 1000 time-stamped data points
List Price $743.00
Starting At $705.85
Stock Drop Ships From Manufacturer  
Thermo Orion Star A221 Portable pH Meter

The waterproof, battery-operated Thermo Orion Star A221 portable pH meter stands up to the most demanding field applications and delivers over 800 hours of continuous operation. The meter displays pH, mV and temperature readings on a large, backlit LCD screen and automatically locks in stable readings.

The Thermo Orion Star A221 portable meter provides a large storage capacity for time-stamped data points, which can be conveniently uploaded to a PC through the meter's USB and RS-232 ports. Automatic or 1 to 5 point manual calibration makes instrument setup simple, while icons provide quick updates on battery life, electrode status and calibration information. The simple button layout and on-screen messages also assist with calibration and explain setup menu choices.


  • AUTO-READ function alerts user and locks on-screen readings when stable
  • Up to 5 point pH calibration
  • Automatic recognition of USA/NIST and DIN buffers
  • Easy to recall calibration slope data for procedure checks
  • Non-volatile memory holds up to 1000 data points
  • USB and RS-232 ports to upload data and update included data analysis software
  • Universal power supply or battery power option
  • Includes (4) AA batteries to provide over 800 hours of operation
  • Universal power adapter (sold separately) runs meter on AC power
  • Multilanguage interface supports English, Spanish, French, Italian, German and Chinese
  • IP67-rated waterproof housing (can be immersed up to one hour with no water incursion) 3 year meter warranty
  • pH
  • Range: -2.00 to 20.00
  • Resolution: 0.1, 0.01, 0.001
  • Relative Accuracy: +/-0.002
  • Calibration Points: Up to 5
  • mV/RmV
  • Range: +/-2000.0 mV
  • Resolution: 0.1 mV
  • Relative Accuracy: +/-0.2mV or 0.05%, whichever is greater
  • EH ORP Mode: Yes
  • Temperature
  • Range: -5 to 105 C
  • Resolution: 0.1
  • Relative Accuracy: +/-0.1 C
  • Offset Calibration: 1 point
  • Datalogging
  • Number of Points: 1000 with time and date stamp
  • Log Function: Manual, Automatic with AUTO-READ
  • Log Edit: Delete last reading or all
  • General
  • Display: Backlit LCD
  • Inputs: pH Electrode - BNC, ATC Probe - 8-pin mini-DIN
  • Outputs: RS-232, USB
  • Power Adapter: Universal AC, 100-240 VAC
  • Battery Power: 4 AAs, 800 hrs life
  • Environmental Requirements: 5 to 45 C and 5 to 85% relative humidity, non-condensing
  • Regulatory and Safety: CE, TUV 3-1, FCC Class A
  • IP Rating: IP67, waterproof
  • Warranty: 36 months (from date of purchase)
Questions & Answers
Does my meter have an alert when it needs to be recalibrated?
Yes, the Star A221 Portable Meter features a calibration due alarm. The alarm will be triggered if a 12 hr period passes without a calibration.
Did you find what you were looking for?

Select Options

  Products 0 Item Selected
Part #
Thermo Orion Star A221 Portable pH Meter
Orion Star A221 pH Portable Meter
Drop Ships From Manufacturer  
Thermo Orion Star A221 Portable pH Meter
Orion Star A221 pH Portable Meter Standard Kit
Drop Ships From Manufacturer  
Thermo Orion Star A221 Portable pH Meter
Orion Star A221 pH Portable Meter General Purpose Kit
Drop Ships From Manufacturer  
Thermo Orion Star A221 Portable pH Meter
Orion Star A221 pH Portable Meter ORP Kit
Drop Ships From Manufacturer  
Thermo Orion Star A221 Portable pH Meter
Orion Star A221 pH Portable Meter Food Sample Kit
Drop Ships From Manufacturer  
  Accessories 0 Item Selected
Notice: At least 1 product is not available to purchase online
Multiple Products

have been added to your cart

There are items in your cart.

Cart Subtotal: $xxx.xx

Go to Checkout

In The News

Penobscot Indian Nation Safeguards Tribal Waterways

Tribal members of the Penobscot Indian Nation have long believed that the Penobscot River was the lifeblood of their people, providing food and transportation needed to support survival. Clearly, keeping water quality good in the river is of concern to natural resource managers with the tribe. But the Penobscot River is not the only waterway that flows through tribal lands. There is Dolby Pond, a prominent water body in the state of Maine monitored in recent years by a sensor-equipped floating platform, and many other streams and creeks that trickle through the nation’s territories. For these, natural resource managers make routine trips to monitor their health, relying on significant parameters like temperature, conductivity, dissolved oxygen and pH.

Read More

Choosing The Right Thermo Portable For Your Project

With so many options in Thermo Scientific’s Orion Star A line, it can be difficult to narrow down which meter will best fulfill a project’s needs. One easy way to rule out some meters is by considering application type. For projects that rely largely on collecting samples in the field, a portable meter is clearly the way to go. But there’s still a handful of meters to choose from. To simplify making the right choice, we spoke with Ricki Hartwell, the global product manager for Thermo Scientific’s Orion Laboratory and Field Instruments. She recently shared her tips on choosing the right Thermo benchtop. Let’s take a look at her recommendations for selecting the right portable meter.

Read More

Thin Ice: Year-Long Monitoring in Missouri Reservoirs

The value of multi-lake studies is well understood by international organizations like the Global Lake Ecological Observatory Network (GLEON) and the scientists who work tirelessly to provide data to the larger network. Rebecca North, an associate professor at the University of Missouri-Columbia , is one of many researchers involved in multi-lake research initiatives and conducting research locally in her home state. Having been born and raised on the shore of Lake Ontario, North grew up in a community that revolved around water. She also saw firsthand one of the worst water quality bodies of the world, the Bay of Quinte, decline throughout her lifetime.

Read More