Calibration and Maintenance of Your pH Meter

Whether it’s soil, water, or hydroponic nutrient solution, pH measurement is an important aspect of successful gardening and plant growth. So, in this article, you find the best soil ph tester.

Healthy plant growth depends on the correct synthesis of an ideal environment for your fruits, vegetables, and ornamental plants. While adjusting the pH level in soil or water can help plants thrive, an incorrect pH value can lead to disease or even death.


What is pH?

PH is an abbreviation for the ‘potential of hydrogen’, which is determined by the quantitative ratio of H + and OH- ions in water and reflects the degree of acidity or alkalinity of the medium. The standard pH scale ranges from 0 to 14, although these levels can be exceeded. The higher the pH, the greater the alkalinity of the substance. The lower the pH, the more acidity. PH 7.0 is neutral.

How can you measure pH?

Although it is not possible to visually determine the pH level of a liquid, soil pH often affects its color. Green soil tends to be more alkaline, while yellow or orange soil shades tend to be more acidic. Soil pH can be measured with a pH meter that is specially designed for soil research or with a pH meter for liquid using a special method.

The pH level of a liquid can be measured with reagents placed on paper test strips or liquid drops, or with a digital pH meter. Testing with a reagent strip or drip test involves using a color matching method. While they are initially inexpensive, they end up costing more than a pH meter. More importantly, stripes and blobs have a shelf life, do not provide high accuracy, and color matching is imprecise and controversial in practice. For example, most bars show an increase in pH in 0.5 increments. Therefore, when using a pH strip, the difference between pH 7.0 and pH 8.0 will only be held in two different shades of pink. What about the roughly 7-10% of people who are color-blind? A digital pH meter, on the other hand, provides a display of the pH level on the instrument display,

It is important to note that pH meters for soil and liquid have very different sensors and should always be used appropriately.

How does a pH meter work?

Despite the different types of pH meter electrodes, ranging from inexpensive pocket-size models to laboratory models that cost tens of thousands of dollars, the most common is a glass bulb with an integrated sensor. The PH meter electrode measures the activity of hydrogen ions by applying a small amount of sensor voltage to the bulb. The pH meter then converts the voltage to pH value and displays it on the instrument’s display.

In addition, many digital pH meters have a built-in thermometer that automatically adjusts to any deviation from the 77ºF (25 °C) baseline. This function is called Automatic Temperature Compensation (ATC).

What is calibration and why is it needed?

Calibration is akin to tuning, and just like a musical instrument, which must be tuned from time to time, a scientific instrument must be calibrated to achieve accurate test results.

Although some people may have perfect pitch and can tune a musical instrument without using a tuning fork, the pH meter must be calibrated correctly by comparing it to a laboratory-certified standard reference point, more commonly known as a calibration buffer. Buffers are liquid, but can also be purchased as a powder for mixing with distilled water to create a fresh solution at the right time.

Any scientific instrument should be calibrated as close as possible to the level to be checked (measured). If a pH range test is to be performed, the instrument should be calibrated in the middle of this range. For example, if testing is to be done in acidic solutions, the pH meter must be calibrated to pH 4.0 for more accurate results. Most waters fall in the pH 6.0 to pH 8.0 range. Therefore, to check the pH level of the water, calibrating the instrument with a pH value of 7.0 will be sufficient. The three most common pH levels for calibration are 4.0, 7.0, and 10.0. These points cover a pH range of 0 to 14, although other pH calibration points exist.

PH meters are available with one-, two-, or three-point calibrations for accurate results. Some pH meters can be calibrated at one point, but manufacturers usually recommend at least two points for calibration for optimal testing. Differences depend on the manufacturing technology of the device and the type of sensor used.

If you have a buffer solution (s) for calibrating pH meters, the process is usually straightforward.


The pH meter, whether analog (dial) or digital (displays the pH level on the screen), will be equipped with analog or digital calibration. The analog calibration is done using a small screwdriver to adjust the value on the display until it matches the buffer value. Digital calibration is carried out by pressing the up and down arrows until the value matches the value of the buffer solution. The digital pH meter can have an analog calibration method.

Some pH meters are equipped with automatic calibration, in which case the instrument will automatically recognize the buffer solution values ​​and calibrate itself to this value. This is by far the easiest calibration method, but it is important that these pH meters also have the ability to manually calibrate for fine-tuning and/or troubleshooting.

Many pH meters are factory calibrated and ready to use right out of the box. However, factory calibration should only be considered for initial use; calibration may change during shipping and it is also possible that factory calibration may not be sufficient for your needs. And as mentioned above, all pH meters must be calibrated by the user.

Regardless of which calibration method your pH meter uses, always read your meter’s instructions carefully and calibrate according to the manufacturer’s recommendations.

For the best measurement results, the pH meter should be calibrated:

With regular use, at least once a week
If not used, at least once a month
If you suspect the reading is incorrect
If aggressive liquids (very acidic or very alkaline) are tested )
If liquids are tested over a wide measuring range
After replacing the electrode

How to properly care for a pH meter?

Although there are general methods for caring for pH meters, each brand and model may have its own requirements. Always follow the instructions for your pH meter and you will be using it for a longer time and with fewer questions.

In addition to periodic calibration, proper care of the pH electrode will ensure a long service life and more accurate results. Many pH meter electrodes consist of a glass bulb with an internal sensor that must be kept in a special solution. When using a portable pH meter, the storage solution must be in the protective cap of the instrument. Do not let this solution pour out of the cap … you really need it! For most pH meter electrodes, it is very important that it is stored in the humid environment of an appropriate storage solution.

To clean most pH meter electrodes, it is enough to rinse them in distilled (deionized) water. Shake off excess water and return to storage in a humid storage solution environment. When measuring solutions that may contaminate the electrode surface, use a cleaning solution, or even leave the electrode in it for a long time.  

See tips for cleaning pH electrodes and JDG meters.

Most pH meter electrodes have a lifespan of approximately 1-2 years. If you experience unstable and incorrect measurements and are having difficulty calibrating, it may be time to replace the electrode (or your pH meter if the electrode is not replaceable).

Tips & Tricks

Always read the instructions carefully before use. Of course, the instructions can be boring, but they can answer your questions, and the answers to these questions will protect your money spent on the purchase.
Always make sure your pH meter is calibrated.
If there is a storage solution in the protective cap of your portable pH meter, it is advisable to store it upright for more effective saturation.
Never touch the electrode: sebum will affect the readings and may even damage the pH meter electrode
During measurements and calibration Always stir the electrode lightly in the liquid to get rid of any possible air bubbles
Never store the pH meter in high temperature and humidity conditions
Never store the electrode pH Meter in Distilled Water The
pH meter is a sensitive scientific instrument and should always be treated as such.

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