You could list off thousands of different circumstances where it’s necessary to measure pH, and almost as many tools designed to help with the task. But like with most measurement devices, finding the right tool for your job specifically is as important as ever. When it comes to measuring equipment, you tend to get what you pay for, except for when you don’t understand what you’re buying. Without careful selection, it’s easy to end up paying for features that aren’t going to help you out, or to miss out on features that could’ve’ made your job far easier.
A pH scale measures the acidity or alkalinity of a substance, ranging from 1 to 14. As you might imagine, there’s a huge range of pH meters, from meters designed for one specific task to more versatile designs. Some take direct measurements with the use of a probe, and others make use of a chemical analysis called titration.
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A pH scale may be portable and versatile, or heavy and specialized. For example, digital pH meters are used widely in the food industry. Creating safe canned foods involves maintaining a careful pH balance, which is particularly important for acidic foods that are close to the canned food pH limit of 4.6. Wineries make use of pH monitors for routine analysis of their stock. It all depends on what you’re looking for.
Advanced pH meters support multi-function purposes with adaptable sensors that can measure things like dissolved oxygen, resistivity, conductivity, redox potential, specific ions, and salinity. While you might need some of those features for specialized roles in water treatment, you don’t want those features bundled with the pH meter if you’re not going to end up using them. And most people don’t need their pH meter to double as a meter for salinity.
Choosing a Digital pH Meter
There are dozens of ways to measure pH, but the most ubiquitous solution for general purpose testing is a digital pH meter. Test and strip indicators are reasonably accurate for testing pools and aquariums at regular intervals, but they’re not ideal for repeated application because tests can cost a few dollars each. For regular analysis, a pH meter is a worthy investment over dealing with inefficient and costly disposable testing. Dedicated pH meters are a great solution for simple base titrations and similar pH measurements.
Required Accuracy
You’ll want to think about the precision you’ll need from your pH meter. For reporting pH to the federal government, most agencies require readings which are listed to one tenth of a unit. However, meeting the 0.1 pH standard is somewhat more difficult if the substances you’re measuring are close to the limit of what’s an acceptable pH level. That’s because for most digital pH meters, the accuracy of pH will be plus or minus 0.2 pH, which can actually be problematic.
For example, beets have a pH that’s very near the limit of 4.6 pH limit for canned goods. If you were measuring beets and got a reading that was on the fence but safe, that measurement can be dangerous if your instrument is actually off by 0.2 pH in either direction.
Such problems should be a serious consideration for anyone operating with substances that approach pH tolerance limits. Those people will want a pH meter with an accuracy of +/- 0.01 pH for confident results. An accuracy of plus or minus 0.2 pH is suitable for applications where you only need a confident ballpark of where the pH is, like with most types of soil testing.
Calibration
Calibration is another thing to consider. Any measuring instrument will eventually need calibration to check it against a standard. Ensuring accuracy is necessary because using even a finely calibrated instrument will inevitably wear down its accuracy with time. Digital pH meters are no exception, and need to be calibrated with colored liquids that have known pH values.
Reading Temperatures
Temperature is another consideration. All pH readings will be affected by temperature. For accuracy, your pH meters need to be carefully calibrated to be the same temperature as the sample you’re testing. Undergoing manual calibration is unnecessarily time consuming and can be inaccurate, so temperature compensation features are a potent convenience that usually adds little cost to a digital pH meter. But the range of temperature support between devices will range drastically, as some provide far better ranges than others.
Other Considerations
Can you connect the pH meter to other devices How’s the response time of the testing? Even if a digital pH meter is highly accurate, it might not be acceptable for you to have to wait 45 seconds to get each and every result. How quick a measurement can be taken is largely dependent on the electrode you use and the meter. And you can find wild differences in response times between brands.
Digital pH meters use an electrode that’s immersed inside the solution you’re testing to measure pH. You may want to think about the cost of replacing that electrode. Some pH meters use special electrodes with a non-clog tip that’s useful for measuring things that aren’t easily mixed and blended, but all electrodes will eventually succumb to wear-and-tear and need replacement.
The glass bulb electrodes used by most digital pH meters are either refillable or sealed. Sealed require little maintenance and are easy to use. Refillable last longer because they can be cleaned when their performance starts to dip, but are less likely to be waterproof.
Dr. Meter PH838
If your primary objective is to avoid having to go through stacks of expensive testing strips, then you’re looking for something accurate enough to be reliable, but nothing so strong that you’d find it in a state of the art lab. What you’re looking for is the Dr. Meter PH838, which is ideal for swimming pools, monitoring water treatment, hydroponics, and pH education.
Testing and Accuracy
The PH838 supports a full 0-14 pH testing range, with a 0.01 resolution for your results. It also makes use of automatic temperature compensation to help accommodate fluctuating temperatures, ensuring you only get accurate readings. Compensation provides a working temperature range of 32 to 122°F, which should be enough for most everyday applications. And properly calibrated, this meter is accurate to 0.02 pH, which also should match or exceed the requirements of any common testing.
Build & Design
The PH838 uses a portable handheld design powered, by four 1.5 volt LR44 button cell batteries. Nobody likes dealing with button cell batteries, but LR44s are very inexpensive and relatively common, so replacement isn’t a particularly arduous experience.
You may appreciate that the PH838 can be toggled to audibly speak the temperature so you don’t have to read the screen yourself. If you stick to reading the LCD, you’ll find it’s both readable and well backlit.
This meter includes a 30-day money back, 12-month exchange warranty. It also includes the four button cell batteries, a user manual, six calibration packets, and a light carrying case.
Apera Instruments AI209 PH20
For some brands, a pH meter is just one of hundreds of products they create. Apera Instruments specializes pH sensors and meters, and their expertise shows in every one of their products. The AI209 PH20 uses some of the same sensor technology you’ll find in top-shelf Apera products, but without the price to match. As a result, it offers fast response times that you can’t typically find on devices in this price range.
Testing and Accuracy
This pH meter is optimal for pools, spas, water treatment, winemaking, and similar common applications. As you would hope, Apera’s PH20 includes a full pH 0 to 14 testing range. It also uses an automatic temperature compensation feature to help ensure the accuracy of your results, as long as you’re within the supported 32 to 122°F testing range. From within that range, your results will be accurate to a precise +/- 0.1 pH, and temperature measurements remain accurate to within half a degree Celsius.
The PH20 has auto calibration, and supports a self-diagnosis feature to alert you if out-of-range measurements are taken, or if calibrations are likely to be incorrect. Auto recognition circuits help remember stable values for consistent measurement, which result in more reliable calibration no matter how long you end up using the device.
Build & Design
Apera’s PH20 uses a relatively large LCD to display discovered pH values, as well as temperature results. The sensor is made from a sealed glass bulb that’s ideal for water testing, and paired with an IP67 waterproof rating that’s equipped for temporary submersion in water.
The included four AAA batteries offer as much as 2,000 hours of constant operation before they need to be changed. Apera’s kit also includes a sturdy carrying case, 1oz pre-mixed bottles of calibration solutions which will be good for 10 or 15 calibrations. Finally, there’s a two-year warranty, though understandably the warranty is limited to six months for the probe.
Milwaukee MW102 PH and Temperature Meter
Milwaukee Instruments is an internationally trusted brand for pH measuring equipment, with a variety of thermometers, pocket meters, and other pH test kits. Their digital pH meters are one step in a long line of expertly designed generalized and specialized instruments.
The MW102 PH is their standard pH meter, built to provide quick and reliable measurements without any unnecessary features tagged on to run up the price. But at a glance you’ll be able to tell that Milwaukee’s idea of standard is very different from other pH meters.
Testing and Accuracy
The MW102 uses a microprocessor to have an extended -2 to 16 pH testing range, and has a pH resolution of 0.01 pH for precise results you won’t find on cheaper products. It also sports a highly precise +/- 0.02 pH accuracy for all your measurements.
The automatic temperature compensation is far more than you’ll find in most standard units, supporting a vast 23-158°F temperature range, with automatic compensation to match. The accuracy of temperatures isn’t as precise as this device is with its pH measurements, but remains within an acceptable margin of error of one half degree Celsius.
Build & Design
This pH meter is powered by one included nine-volt battery, which will prepare the device for 300 hours of continuous use. The auto-off feature is convenient because it only kicks in after 8 minutes of not being used, which shouldn’t interrupt your measurements. And the stainless steel temperature probe is both made to last and fully replaceable, ensuring the unit can last for years to come.
Choosing Between 3 Quality Digital pH Meters
If you’re looking for something inexpensive and simple, the Dr. Meter PH838 is up to most tasks. It uses a small compact design that’s suited to occasional use, and would be comfortable inside most any toolbox. It’s only substantial downside is that testing times for products in this price range are relatively slow. There’s also no detachable probe, so the range of your testing is slightly more limited than with other meters, but the slim profile of the design ensures that won’t often be a problem.
Apera Instruments’ AI209 PH20 is a step up from the PH838. If you’re doing more than a couple of tests at a time, then you’re not going to like the slower response times from units like the PH838. The AI209 uses Apera’s powerful sensor technology for fairly rapid response times. And as a minor bonus, the AI209 uses AAA batteries that are far more convenient than dealing with button cells.
Finally, the Milwaukee MW102 PH is your choice if a detachable testing probe is non-negotiable, or if you need remarkable 0.02 pH accuracy from your results. It’s a laboratory quality instrument a considerable testing range, both physically and functionally. And because the MW102 is only a pH meter, it has an insane price to performance ratio for an instrument of this caliber.
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