Selecting, using, and caring for pH meters seem like complicated concepts. This article will answer all the questions you were too afraid to ask, did not know whom to ask, or did not know needed to be asked.
There are three styles of pH meters: pen or pocket style, portable handheld, and bench top. The important specifications include precision, calibration, and temperature correction, stated as ATC for automatic temperature correction.
Precision: For brewing, it is good to have a precision of ±0.01 pH units or at the least ±0.02 pH units. At this level you will be able to detect even yeast autolysis. Remember, when you read an article that mentions pH units in tenths (e.g., mash should be between 5.3-5.7), you want one additional digit to better determine how close you are to that level. If you don’t have that precision, your mash could be at pH 5.78 and not know how close you are to 5.70 or 5.79. The pH scale is logarithmic, which means each pH gradation is ten-fold higher, so pH 6.0 is ten times as much as pH 5.0.
Calibration: Calibration is tuning the pH meter to a known pH buffer value. There are two types of calibration available: automatic and manual. In automatic calibration, the pH meter will automatically recognize the value of the pH buffer solution and calibrate itself to that value. In manual
There are two types of calibration available: automatic and manual. In automatic calibration, the pH meter will automatically recognize the value of the pH buffer solution and calibrate itself to that value. In manual calibration it is necessary to tell the pH meter what value the pH electrode is immersed. The pH meter will get close to the value and then, with minor adjustments, the user must manually correct it. Manual calibration offers accuracy while automatic calibration offers simplicity. Generally, automatic calibration is the most common in the price range most homebrewers seek. You may consider purchasing a pH meter with automatic calibration that has a manual adjustment mode. Some of these can be purchased at a moderate price.
Temperature correction: The measurement of pH is temperature dependent; its value will change depending on the temperature of the test sample. It is important that pH measurements are performed at the same temperature as the calibration solution. Calibration buffer solutions are almost always made to be read at room temperature (generally 25°C or 77°F). If you are close to this range, you are fine. What this means is that deviations of the test sample, either hotter or colder, from the calibration will be imprecise. Test samples must be stabilized as close to room temperature as possible. This is where temperature correction fits. If the test sample is a little warmer or cooler than the pH buffer solutions, the actual pH measurement can be compensated by either manual temperature or automatic temperature compensation. In manual compensation, the user must enter the temperature of the sample so that the pH meter can correct the value of the pH. In automatic compensation, the pH meter will read the temperature of the sample and do it by itself. There are two important points to note here:
1) The actual change in solution pH varies due to the chemicals in it (i.e., sugar, starch, protein, salts/ions, etc.). It is difficult to know how much the wort pH shifts with each degree rise or fall in temperature from the calibration temperature.
2) It is not a good idea to read extreme temperatures (too hot or too cold), such as of a mash or beer lagering near freezing. Doing so will hasten the end-life of the pH probe.
One feature you may want to consider is to get a pH meter that has a replaceable probe. While it may be more expensive, it is less expensive than purchasing a replacement pH meter. There are other specifications that you may see as you shop for pH meters:
• Probe connection (usually for benchtop models; BNC is the most common connector),
• mV readout (milliVolt; determines the slope between pH calibration points),
• Total dissolved solids (TDS),
• Oxidation-reduction potential (ORP),
• Refillable pH electrodes ,
• pH probe with a single or double junction.
Most conventional pen or pocket pH meters are non-refillable, single junction (lower maintenance and cost). The other specifications listed here will not be discussed as they are features that are outside the scope of this article. While they add functionality, they also add complexity and raise the price.
Before using a pH meter, it must be calibrated at least once a week, if used routinely. If it is used infrequently, it must be calibrated before the pH measurement session begins. Regardless of the type of calibration available in the pH meter (manual or automatic), three types of calibrations may be performed: single, two point or three point. Three point calibrations are less common and are available in higher end models used for analytical work. Single point calibration is suitable if the solution being measured is near neutral (between pH 5.5-8.5) For brewing, a two-point calibration is highly recommended. Calibration buffers are available at different pH. The pH buffers you will commonly see are: 4.01, 6.86, 7.01, and 10.01. Choose the two calibration buffers that most closely bracket the solution being measured. It is best if the pH buffers are one to three pH units apart. For brewing, it would be 4.01 and either 6.86 or 7.01.
General calibration instructions are provided, but it is best to read the pH meter instruction manual. The buffer or sample level must be above the pH electrode reference junction when the electrode is immersed in the solution. This means the pH probe should be immersed in 1-2 inches of sample.
Allow the calibration buffers to settle at room temperature. Enter the calibration mode of the pH meter. Rinse the pH electrode with deionized or distilled water (tap water may be fine). Do not allow the rinse to contaminate any of the buffers. Immerse the pH electrode in the first calibration buffer. The pH meter will either prompt you or you may have to tell it in which buffer it is immersed. Gently stir the pH electrode until it reads the proper pH. When the reading stabilizes, either prompt the pH meter to recognize and save that value (manual calibration) or allow it to callibrate by itself (automatic calibration).
Rinse the pH probe with deionized or distilled water (tap water may be fine). Either gently shake the water off the pH probe or blot dry with a clean tissue or paper towel. Do not touch the actual electrode or wipe the pH electrode. You only need to get most of the adhering water off of it.
Calibrate the pH meter to the next buffer solution. Immerse the pH probe into the second calibration buffer, stir gently, and when the reading stabilizes, either prompt the pH meter to recognize and save that value, or it may calibrate automatically. Then, exit the calibration mode. If the meter auto calibrates, it may do this automatically. Rinse the pH probe with deionized or distilled water (tap water may be fine), gently shake off excess water or blot (never wipe), and place it either into the pH electrode storage solution or into the sample to be measured. After measuring the sample, rinse well, and place the electrode into the storage solution.
As an optional check, to test the calibration, you could enter pH reading mode (not calibration mode), and place the pH probe in each of the pH buffers used for calibration. Make sure to rinse the pH probe between buffers.
Because pH measurements are temperature dependent, make sure the solution being measured is as close to room temperature as possible. Remember, slight deviations from room temperature are fine, but extremes should be avoided. After calibration, enter pH reading mode. Rinse the pH electrode with deionized or distilled water (tap water may be fine), shake or blot excess water, immerse the pH probe into the sample, and stir gently. Wait for the reading to stabilize, and record the pH. Remove the pH probe from the sample, rinse it with deionized or distilled water (tap water may be fine), shake or blot excess water, and place the pH probe into the pH storage solution. As stated previously, it is not necessary to recalibrate the pH meter between samples read on the same day or week unless issues are noted and is covered in the next section.
These are universal and general guidelines, so check the instruction manual for specifics:
• Never store the pH meter in distilled or deionized water; Always store the pH meter in pH storage solution.
• Never allow the pH probe to be stored dry.
• It is preferred to not store the pH probe for long term in pH Calibration Buffer – pH Storage Solution is best.
• To clean a pH probe, rinse in distilled or deionized water (tap water may be fine). Shake off any excess water, or blot and return the pH meter to its storage solution.
• Do not wipe the pH probe with any type of cloth or tissue; static charge can develop and give faulty readings, or the probe can become damaged.
• Do not touch the pH probe with your fingers. Oils will contaminate the pH probe, give faulty readings, and can shorten the probe’s life.
• Bring all solutions as close to room temperature as possible. Extreme temperatures will shorten the life of the probe.
• With proper care, pH probes will generally last about two years.
• Clean pH probes with pH probe cleaning solution.
• Pay attention to how long it takes your pH meter to get close to the pH with gentle stirring before it stabilizes (usually about 1 minute). Dirty pH probes, or if probes nearing end of life, will not stabilize as quickly. If the time is longer or if the reading does not stabilize, clean the probe with probe cleaning solution, store the probe overnight in storage solution, and recalibrate. Consult the probe owner’s manual for detailed information.
• Remember, a pH meter is a sensitive scientific instrument and should always be treated with care.
Hopefully, most of your questions on pH meters have been answered. The methods discussed here allow you to better follow your mash and fermentation and determine factors that contribute to the health of your yeast.
Selecting a pH Meter
There are three styles of pH meters: pen or pocket style, portable handheld, and bench top. The important specifications include precision, calibration, and temperature correction, stated as ATC for automatic temperature correction.
Precision: For brewing, it is good to have a precision of ±0.01 pH units or at the least ±0.02 pH units. At this level you will be able to detect even yeast autolysis. Remember, when you read an article that mentions pH units in tenths (e.g., mash should be between 5.3-5.7), you want one additional digit to better determine how close you are to that level. If you don’t have that precision, your mash could be at pH 5.78 and not know how close you are to 5.70 or 5.79. The pH scale is logarithmic, which means each pH gradation is ten-fold higher, so pH 6.0 is ten times as much as pH 5.0.
Calibration: Calibration is tuning the pH meter to a known pH buffer value. There are two types of calibration available: automatic and manual. In automatic calibration, the pH meter will automatically recognize the value of the pH buffer solution and calibrate itself to that value. In manual
There are two types of calibration available: automatic and manual. In automatic calibration, the pH meter will automatically recognize the value of the pH buffer solution and calibrate itself to that value. In manual calibration it is necessary to tell the pH meter what value the pH electrode is immersed. The pH meter will get close to the value and then, with minor adjustments, the user must manually correct it. Manual calibration offers accuracy while automatic calibration offers simplicity. Generally, automatic calibration is the most common in the price range most homebrewers seek. You may consider purchasing a pH meter with automatic calibration that has a manual adjustment mode. Some of these can be purchased at a moderate price.
Temperature correction: The measurement of pH is temperature dependent; its value will change depending on the temperature of the test sample. It is important that pH measurements are performed at the same temperature as the calibration solution. Calibration buffer solutions are almost always made to be read at room temperature (generally 25°C or 77°F). If you are close to this range, you are fine. What this means is that deviations of the test sample, either hotter or colder, from the calibration will be imprecise. Test samples must be stabilized as close to room temperature as possible. This is where temperature correction fits. If the test sample is a little warmer or cooler than the pH buffer solutions, the actual pH measurement can be compensated by either manual temperature or automatic temperature compensation. In manual compensation, the user must enter the temperature of the sample so that the pH meter can correct the value of the pH. In automatic compensation, the pH meter will read the temperature of the sample and do it by itself. There are two important points to note here:
1) The actual change in solution pH varies due to the chemicals in it (i.e., sugar, starch, protein, salts/ions, etc.). It is difficult to know how much the wort pH shifts with each degree rise or fall in temperature from the calibration temperature.
2) It is not a good idea to read extreme temperatures (too hot or too cold), such as of a mash or beer lagering near freezing. Doing so will hasten the end-life of the pH probe.
One feature you may want to consider is to get a pH meter that has a replaceable probe. While it may be more expensive, it is less expensive than purchasing a replacement pH meter. There are other specifications that you may see as you shop for pH meters:
• Probe connection (usually for benchtop models; BNC is the most common connector),
• mV readout (milliVolt; determines the slope between pH calibration points),
• Total dissolved solids (TDS),
• Oxidation-reduction potential (ORP),
• Refillable pH electrodes ,
• pH probe with a single or double junction.
Most conventional pen or pocket pH meters are non-refillable, single junction (lower maintenance and cost). The other specifications listed here will not be discussed as they are features that are outside the scope of this article. While they add functionality, they also add complexity and raise the price.
Using a pH Meter - Calibration
Before using a pH meter, it must be calibrated at least once a week, if used routinely. If it is used infrequently, it must be calibrated before the pH measurement session begins. Regardless of the type of calibration available in the pH meter (manual or automatic), three types of calibrations may be performed: single, two point or three point. Three point calibrations are less common and are available in higher end models used for analytical work. Single point calibration is suitable if the solution being measured is near neutral (between pH 5.5-8.5) For brewing, a two-point calibration is highly recommended. Calibration buffers are available at different pH. The pH buffers you will commonly see are: 4.01, 6.86, 7.01, and 10.01. Choose the two calibration buffers that most closely bracket the solution being measured. It is best if the pH buffers are one to three pH units apart. For brewing, it would be 4.01 and either 6.86 or 7.01.
General calibration instructions are provided, but it is best to read the pH meter instruction manual. The buffer or sample level must be above the pH electrode reference junction when the electrode is immersed in the solution. This means the pH probe should be immersed in 1-2 inches of sample.
Allow the calibration buffers to settle at room temperature. Enter the calibration mode of the pH meter. Rinse the pH electrode with deionized or distilled water (tap water may be fine). Do not allow the rinse to contaminate any of the buffers. Immerse the pH electrode in the first calibration buffer. The pH meter will either prompt you or you may have to tell it in which buffer it is immersed. Gently stir the pH electrode until it reads the proper pH. When the reading stabilizes, either prompt the pH meter to recognize and save that value (manual calibration) or allow it to callibrate by itself (automatic calibration).
Rinse the pH probe with deionized or distilled water (tap water may be fine). Either gently shake the water off the pH probe or blot dry with a clean tissue or paper towel. Do not touch the actual electrode or wipe the pH electrode. You only need to get most of the adhering water off of it.
Calibrate the pH meter to the next buffer solution. Immerse the pH probe into the second calibration buffer, stir gently, and when the reading stabilizes, either prompt the pH meter to recognize and save that value, or it may calibrate automatically. Then, exit the calibration mode. If the meter auto calibrates, it may do this automatically. Rinse the pH probe with deionized or distilled water (tap water may be fine), gently shake off excess water or blot (never wipe), and place it either into the pH electrode storage solution or into the sample to be measured. After measuring the sample, rinse well, and place the electrode into the storage solution.
As an optional check, to test the calibration, you could enter pH reading mode (not calibration mode), and place the pH probe in each of the pH buffers used for calibration. Make sure to rinse the pH probe between buffers.
Using a pH Meter – Sample Measurement
Because pH measurements are temperature dependent, make sure the solution being measured is as close to room temperature as possible. Remember, slight deviations from room temperature are fine, but extremes should be avoided. After calibration, enter pH reading mode. Rinse the pH electrode with deionized or distilled water (tap water may be fine), shake or blot excess water, immerse the pH probe into the sample, and stir gently. Wait for the reading to stabilize, and record the pH. Remove the pH probe from the sample, rinse it with deionized or distilled water (tap water may be fine), shake or blot excess water, and place the pH probe into the pH storage solution. As stated previously, it is not necessary to recalibrate the pH meter between samples read on the same day or week unless issues are noted and is covered in the next section.
Caring for pH Meters
These are universal and general guidelines, so check the instruction manual for specifics:
• Never store the pH meter in distilled or deionized water; Always store the pH meter in pH storage solution.
• Never allow the pH probe to be stored dry.
• It is preferred to not store the pH probe for long term in pH Calibration Buffer – pH Storage Solution is best.
• To clean a pH probe, rinse in distilled or deionized water (tap water may be fine). Shake off any excess water, or blot and return the pH meter to its storage solution.
• Do not wipe the pH probe with any type of cloth or tissue; static charge can develop and give faulty readings, or the probe can become damaged.
• Do not touch the pH probe with your fingers. Oils will contaminate the pH probe, give faulty readings, and can shorten the probe’s life.
• Bring all solutions as close to room temperature as possible. Extreme temperatures will shorten the life of the probe.
• With proper care, pH probes will generally last about two years.
• Clean pH probes with pH probe cleaning solution.
• Pay attention to how long it takes your pH meter to get close to the pH with gentle stirring before it stabilizes (usually about 1 minute). Dirty pH probes, or if probes nearing end of life, will not stabilize as quickly. If the time is longer or if the reading does not stabilize, clean the probe with probe cleaning solution, store the probe overnight in storage solution, and recalibrate. Consult the probe owner’s manual for detailed information.
• Remember, a pH meter is a sensitive scientific instrument and should always be treated with care.
Hopefully, most of your questions on pH meters have been answered. The methods discussed here allow you to better follow your mash and fermentation and determine factors that contribute to the health of your yeast.
