Grow Mediums Guidelines for pH Electrode Maintenance and Use

[IndicaIVoz]

Hi there guys ,I've recently noticed my Ph meter is on the fritz another issue (essentials ph pen not blue lab atm ) so i went hunting for info for better Ph pen storage info because I'm tired of going through them when some people have cheap ones that last 2-3 years + Haha. I've seen other cool info around that may be added to this thread but here's one to start , Anyway it may help others Though this info could be in the sticky section anyway ... Enjoy ....those crystals are normal?..

Guidelines for pH Electrode Maintenance and Use
(This info taken from Hanna instruments site)

The life of a pH electrode is not infinite. A number of factors can affect the life span of a pH electrode. The higher the temperature that the electrode is used at, the more extreme the pH, how often the bulb dries out and needs to be re-hydrated, how roughly it is used; all these factors and more will shorten the life span of a pH electrode. An electrode that is well maintained and cared for can last many years, one that is not well maintained will last anywhere from just a couple of months to 1-2 years.



Following the guidelines outlines below will help to get the most from a pH electrode.



1. Hydration of the glass bulb

A very thin layer of water forms on the pH glass sensor. This layer is known as the hydrated layer. A pH electrode is an electrochemical sensor that generates a voltage that is read by a voltmeter.



A probe that has a hydrated layer will generate a different voltage in a pH buffer than one that doesn’t. So calibrating a dry electrode will cause inaccurate readings when taking measurements as the hydration layer is formed. A dry probe needs to be hydrated before calibration. The hydrated layer takes 3-4 hours to form when a probe is placed into storage solution.



2. Hydration of the junction

Every combination pH electrode has a junction. A junction is a barrier between the internal reference wire and the sample that is measured. The reference cell has a salt solution that leaks through the junction as part of the electrical circuit. If a probe is dry the salt will precipitate in the junction causing to be clogged. The pH readings will be erratic. A dry probe needs to have the junction hydrated to work properly.



3. Fill Solution Level for Refillable pH Electrodes

pH electrodes that are refillable need to have their electrolyte (salt) level checked. The probe should be filled when the level falls below ½” from the fill hole opening. Having enough fill solution ensures that, for a single junction electrode, the reference wire is in solution. A proper level also allows for adequate head pressure to force electrolyte through the junction.



4. Remove/Loosen Reference Fill Cap When in Use

In order to create head pressure the fill cap must be loosened or removed from the top of the electrode. Removing/loosening the reference fill cap allows for air to enter into the reference cell. The solution within the probe will want to flow through the junction resulting in increased stability when taking a reading. Note: Single junction and double junction electrodes use different fill solutions. An explanation of the difference can be found here (hyperlink to single junction versus double junction page).



5. Calibration Buffers

Fresh calibration solution should be used when calibrating a pH electrode. All pH measurements are based on the pH calibration solution as a reference point. The pH calibration buffer is a water-based solution that will change over time. This is especially true with pH 10.01 buffer that will actually decrease in pH as atmospheric carbon dioxide enters the solution. Bottles of buffer should be replaced after they have been opened for 6 months. Never pour calibration buffer back into the bottle.



6. Calibration of the pH Electrode

The pH electrode should be rinsed in purified water (RO, DI, or distilled) before placing in any pH calibration buffer. This will reduce the chance of contaminating the buffer. A best practice would be to use two beakers/containers for each calibration buffer. The process would be to rinse the pH electrode with purified water then rinse the probe in one of the beakers with the buffer then place the probe in the second beaker with buffer. This procedure would be repeated for multiple calibration points. For two point calibration the pH buffers used should bracket the expected pH reading. For example I expect a pH 5 reading then the pH electrode should be calibrated in pH 7 and pH 4 buffers.



7. Cleaning a pH Electrode

The pH electrode should be cleaned periodically. A coating will form on the glass bulb that will cause errors in measurements and drifting/erratic readings. A typical cleaning procedure is to place the electrode in a cleaning solution for 15 minutes. After that the probe is rinsed with purified water and then placed in storage solution for at least 2-3 hours before using. It is important to note that there are many different types of cleaning solutions available based on the application. Solutions include ones for proteins, inorganics, food and wine stains to name just a few.



8. Storage of the pH electrode

The pH electrode bulb and junction needs to be kept hydrated. With benchtop meters a small amount of storage solution is placed in a beaker. With the probe lowered into the beaker the junction should be covered. For portable meters a small amount of storage solution is placed in the protective cap and the cap placed on the probe.



NEVER STORE THE pH ELECTRODE IN PURIFIED WATER

Storing the pH electrode in purified water (RO, DI, or distilled) will shorten the life of your pH electrode.



The reference cell has a high salt solution. Placing the probe in purified water will cause the salt to diffuse out and the water to go in. Storage solution is not only formulated to maintain the reference salt concentration but also has chemicals to keep bacteria and fungus from growing. If storage solution is not available then use pH 4 buffer.





9. Tips

• Salt crystals around the fill cap of a refillable pH electrode or by the protective cap placed over the bulb are normal to see. Just rinse with water to remove the salt build up.
• Any air bubbles in the pH bulb or by the junction need to be removed. Gently shake the pH electrode like a spirit filled thermometer to displace the air bubble.
• Never wipe the pH electrode with a cloth or any other type of material. Any static formed will harm the electrode.
• Do not expose to high temperatures (>150 oF/65 oC) unless the probe is designed for it.
• Always rinse the probe with purified water to clean of contaminants before, during and after use.
• Calibrate frequently. Some guidelines to follow:

1. Periodic user (1-2 times per month) – calibrate the day of use
2. Weekly user (1-2 times per week) – calibrate the day of use
3. Daily user (1-2 times per day) – calibrate the day of use
4. Daily user (>2 times per day) – calibrate every 4-6 hours

 

[IndicaIVoz]

Another one i like..

How to Take Care of your pH Meter

(Just for growers site)Keeping track of the pH of your hydroponic nutrient solution is key to making sure that the right spectrum of nutritional elements are available to your plants as they grow and bloom. But, while you might be measuring your nutrient solution's pH every day, are you taking care of the pH meter itself? Without regular maintenance, pH meters can give increasingly inaccurate readings making your regular monitoring less effective. So take our advice and take care of your pH meter! We will show you how!
Whether in soil, water or a hydroponic solution, measuring pH levels is a critical aspect of successful gardening.

Healthy plant growth depends on properly synthesizing the perfect environment for your fruits, veggies and decorative plants. And just as correcting the pH level in soil or water can help a plant thrive, an incorrect pH level can lead to disease or potential death.

What is pH?
pH is the abbreviation for 'potential of hydrogen' which indicates a substance's acid or alkaline (base) properties. The standard pH scale (occasionally referred to as the acidity or alkalinity scale) goes from 0 to 14, although it is possible to exceed these levels. The higher the pH, the more base or alkaline a substance is. The lower the pH, the more acidic it is. And a pH level of 7.0 is of neutral acidity and alkalinity.

A note to all you beginning gardeners: "Acid" often has a dangerous connotation, but a substance that is too alkaline can be just as dangerous for people and plants. Did you know that bleach has a pH level of 12.0 to 12.6?

How can you measure pH?
Although it is impossible to visually determine the pH level of a liquid, the pH of soil will often affect its color. A greener shade of soil is typically more alkaline, while a yellow or orange tinted soil tends to be more acidic. Soil pH can be measured with a pH test kit or a meter that is specifically designed for soil testing.

The pH level of a liquid can be measured using reagents incorporated into paper strips or liquid drops or with a digital pH meter. Reagent testing strips and drops incorporate color-matching techniques. While they are initially inexpensive, they will ultimately cost more than a pH meter. More importantly, strips and drops have a shelf life, do not provide pinpoint accuracy, and the color matching is open to interpretation. For example, most strips will show an increase of pH levels by increments of 0.5. Therefore, when using a pH strip, the difference between pH 7.0 and pH 8.0 will only be two different shades of pink. And what about the roughly 7% of males in the United States that are color blind? A digital pH meter, on the other hand, provides a pH level display screen, so there is no interpretation required: a user simply inserts the meter into a solution and views the digital reading.

It is important to note that soil and liquid pH meters have very different probes and should always be used accordingly. Make sure you have the right one for your needs.

How do pH meters work?
Even though there are a variety of pH probe types, ranging from inexpensive handhelds to laboratory models that cost tens of thousands of dollars, the most common pH meters incorporate a glass sensor and a reference tube. The pH probe measures the activity of hydrogen ions by generating a small amount of voltage across the sensor and the reference tube. The meter then converts that voltage to a pH value and displays it on a digital screen.

Also, many digital pH meters have a built-in thermometer that automatically adjusts for any discrepancies off the baseline of 77ºF (25oC). This function is called automatic temperature compensation (ATC).

What is calibration and why is it necessary?
Calibration is akin to tuning, and just as a musical instrument must be tuned from time-to-time, a scientific instrument must be properly calibrated to achieve accurate test results.

While some humans may have perfect pitch and can tune a musical instrument without the use of a tuner, the only certain way to determine if a pH meter is calibrated properly is by comparing it to a laboratory-certified standard reference point, more commonly known as a 'buffer solution.' Buffer solutions are liquid, but can also be purchased in powder form and mixed with distilled or deionized water to create a fresh batch each time.

Any scientific instrument should be calibrated as close as possible to the level that will be tested. If testing a range, then the meter should be calibrated in the middle of that range. For example, if testing an acidic solution, a pH meter should be calibrated to pH 4.0 to achieve the most accurate results. Most waters fall into the range of pH 6.0 to pH 8.0. Therefore, to test the pH of water, calibrating your meter to pH 7.0 will suffice. The three most common pH levels for calibration are 4.0, 7.0 and 10.0. These points cover the pH range of 0 to 14, but other values are available.

A pH meter will require single-, two-, or three-point calibration for accurate results. Some meters can be calibrated to a single point, but the manufacturer will recommend at least two points for optimum testing. The differences will depend on the technology of the meter and the type of sensor it uses.

Once you have a pH buffer solution, calibrating a pH meter is typically a simple process.

A pH meter, whether analog (a needle points to the pH level) or dialog (displays the pH level as a number on the screen), will incorporate either analog or digital calibration. Analog calibration is done by using a small screwdriver to adjust the reading until it matches the value of the buffer solution. Digital calibration is done by pressing up and down buttons until the reading matches the value of the buffer solution. A digital pH meter can have analog calibration.

Some meters also offer automatic calibration, in which case the meter will automatically recognize the value of the buffer solution and calibrate itself to that value. This is by far the simplest method of calibration, but it is important that these meters also have manual calibration for fine tuning and/or troubleshooting.

Many brands of pH meters are factory calibrated and ready to use right out of the box. However, the factory calibration should only be considered a convenience for a few uses; the calibration could shift during shipping, and it's also possible that the factory calibration may not be ideal for your needs. And as mentioned above, all pH meters will need to be recalibrated at some point.

Regardless of what method of calibration your meter employs, always carefully read your meter's instructions and perform calibration according to the manufacturer's recommendations.

For best results, a pH meter should be calibrated:

• With regular use-at least once per week
• If not used-at least once per month
• If you think the readings are incorrect
• If testing aggressive liquids (very acid or basic liquids)
• If testing a wide range of liquids (going back and forth between acids and bases)
• Whenever the sensor is replaced

How should a pH meter be properly cared for?
Although there are general maintenance techniques for pH meters, each brand and model will have its own requirements. Always follow the directions for your meter and you will enjoy it for a longer time, with fewer issues.

In addition to frequent calibration, properly maintaining the pH sensor will ensure a longer life and more accurate results. Many pH meters incorporate glass sensors and reference tubes that must be stored in specially formulated solutions. If using a handheld meter, the storage solution will often be in the meter's cap. Don't spill this solution ... you need it! For most pH sensors, it's critical that the sensor be stored wet in the appropriate solution.

To clean most pH sensors, rinse in distilled or deionized water. Shake off any excess water and return the sensor to its storage solution.

The majority of pH sensors have a lifespan of approximately 1-2 years. If you are experiencing erratic readings and having difficulty calibrating, it may be time to replace the sensor (or your meter, if the meter doesn't have a replaceable sensor).

Tips and tricks

• Always read the instruction manual prior to use. Sure, the instructions may be boring, but they'll answer your questions, and those answers will protect your investment
• Always be sure your pH meter is properly calibrated
• If your handheld meter includes a storage solution in the cap, store the meter upright for more effective saturation
• Never touch a sensor electrode or reference cell with your fingers: skin oils will affect readings and can permanently damage a pH sensor
• Always lightly swirl a meter in the water or solution to dislodge any trapped air bubbles
• Never store a pH meter in high heat or humidity
• Never store a pH sensor in distilled water
• A pH meter is a sensitive scientific instrument and should always be treated as such