How pH Affects Conductivity and the Role of pH and Conductivity Meters

When you measure the quality of a body or sample of water, two of the most important metrics to test for include pH and conductivity. Both measurements can help you determine how contaminated the water is and if it needs to be treated. The water’s pH can be either acidic or alkaline.

When the water is acidic, you may need to take steps to treat it and remove any contaminants. Alkaline water can also cause scale buildup in machinery, boilers, and pipes, which is why many industrial processes must maintain specific pH levels.

Conductivity is another useful metric that informs you of how well the water can pass an electrical current. If the water has high conductivity levels, there are likely too many pollutants in the solution. Low conductivity indicates that the water is clean and healthy to drink.

From soil testing to water treatment, many industries measure pH and conductivity to ensure their processes are completed without issue. It’s possible to measure these two water quality parameters with a pH and conductivity meter. The purpose of this article is to answer the question “How does pH affect conductivity?”.

What Is pH?

Among the most common water quality parameters is pH, which is used to determine if the water is acidic or alkaline. If the substance is balanced, it’s considered neutral. The pH scale measures the alkalinity or acidity of a substance. This scale can range from 0-14.

If you measure water quality and receive a reading of 7.0, this means that the water is neutral and pure. When the pH drops below 7.0, the substance becomes more acidic. A reading above 7.0 indicates that the substance is more alkaline.

Placing different chemicals in the water can cause pH levels to increase or decrease. For example, lemon juice and vinegar are two liquids that can make water more acidic. In comparison, laundry detergents are alkaline. When water is more acidic, it likely contains high levels of contaminants like metal and organic matter. Alkaline water often consists of high concentrations of calcium and magnesium.

Common Applications of pH Measurement

There are many applications where it can be useful to perform pH measurements. For example, municipalities are required to test the drinking water supply to ensure it doesn’t contain many impurities. This testing equipment can also be used to monitor changes to environmental water.

In the food industry, pH sensors allow manufacturers to maintain the quality and specific ratio of different ingredients. Milk needs to reach a certain acidity range to accommodate the production of cheese and yogurt.

As for the agriculture industry, it uses pH testing to check the composition and quality of soil. The pH levels of soil determine which fertilizers should be used and how plants can grow. Crops can only absorb nutrients in highly acidic soil. When looking at the healthcare industry, pH sensors are used to test blood samples for different conditions.

What Is Conductivity?

Conductivity is a measurement that allows you to identify the ability of water to properly pass an electrical current. Everything from inorganic chemicals to dissolved salts is capable of conducting electrical current, which means that conductivity readings will increase as the salinity rises.

Keep in mind that some contaminants don’t conduct electrical current well. For example, oil and similar organic compounds come with low conductivity. Temperatures can impact conductivity readings as well. Warm water causes conductivity to increase.

Conductivity readings can tell you a lot about the quality of water. Most bodies of water have a constant conductivity range that you can use as a baseline for other measurements. If there are any sizable changes to your conductivity readings, this indicates that a notable pollutant has entered the sample.

Importance of Conductivity in Different Contexts

Conductivity measurements can also be obtained for different applications. In natural water or environmental applications, conductivity readings will help you identify the concentration of dissolved salts in the sample. These readings can be used to determine how various processes impact the water’s conductivity. For example, conductivity often increases in river waters during the summer because of the evaporation and transpiration processes. When a heavy storm rolls through or snowmelt accumulates, the conductivity of river waters can drop.

Conductivity measurements in drinking water will tell you if the solution has too much salt to be drinkable. If you’re monitoring water that often becomes polluted, you can obtain regular measurements to determine if conductivity changes might have been caused by a leak or spill.

In industrial applications, the readings you get from a conductivity meter will tell you if the water needs to be treated. For example, it’s common for corrosion and scale to occur in industrial applications. These issues are often caused by high alkalinity in the water. You can perform conductivity measurements to determine if your demineralization treatments have been effective. It’s also possible for conductivity sensors to monitor the potency of the desalinization process.

Conductivity readings play a major role in hydroponics and agricultural applications as well. If the salinity of irrigation is too high, it’s possible for salt to build up in the soil when the water evaporates. In this situation, the soil quality can quickly degrade, which will limit plant growth. If your water has a conductivity of 700 uS/cm or less, you can use it with irrigation applications. If the meter gives you a reading of 3,000 uS/cm or higher, it’s highly recommended that you restrict the use of water for irrigation.

How pH Affects Conductivity

While several factors can impact a conductivity measurement, among the most important is the solution’s pH level. When a solution has lower pH levels, it usually has fewer free ions, which means that the conductivity can be low. Solutions with elevated pH levels typically contain more free ions, which can lead to a high conductivity.

However, this isn’t always the case. The types of substances in the water can impact pH and conductivity differently. If a sample of water has significant pH variations, this means that the number of ions within the sample changes regularly. The types of chemicals that can influence the relationship between pH and conductivity include the following:

• Chloride
• Nitrate
• Sulfate
• Aluminum
• Phosphate
• Magnesium
• Iron
• Calcium
• Sodium

High concentrations of any of these chemicals will lead to an increase in water hardness, which means that the conductivity and pH levels will be elevated.

pH and Conductivity Meters

Whether you need to obtain a pH or conductivity measurement, the most effective way to get an accurate measurement is with the right meter.

Understanding pH Meters

A pH meter is made with a reference electrode, a high-input impedance meter, and an internal electrode. The two electrodes are kept in a glass probe. This probe also contains a buffer solution that has a pH level of 7.0. You can obtain a pH measurement by comparing the reading of a sample to the pH of a buffer.

There are several types of pH sensors. For example, a combination pH sensor is an electrochemical device that allows you to identify the pH of any solution. It’s common for this technology to be used to create process and laboratory pH sensors.

A differential pH sensor comes with three electrodes, the third of which is a metal ground electrode. This design eliminates the potential of reference fouling, which is why it’s often used in heavy-duty industrial applications.

If you need to perform environmental monitoring or pool water testing, you can use a laboratory pH sensor. These sensors are designed specifically for light-duty applications. Process pH sensors have heavier bodies with built-in NPT threads. These sensors can be used to perform continuous pH monitoring in a tank or pipe.

Understanding Conductivity Meters

Conductivity meters are designed to measure the concentration of ions within a solution. They usually come with two electrodes that you’ll need to place directly into the solution that’s being measured. A current of electricity passes between the electrodes to provide a conductivity reading. The electrodes can be made from gold or platinum.

Your sensor will likely be comprised of a measuring electrode and a reference electrode. When considering the reference electrode, it provides a reference voltage that the measurement can be compared with. The measuring electrode is responsible for detecting the current that’s flowing in the solution.

There are two types of conductivity sensors, which include a contacting meter and a toroidal meter. A contacting conductivity meter is designed to have two surfaces come touch the sample. It’s possible for these surfaces to be made from platinum, graphite, or stainless steel. The reading from a contacting conductivity sensor can be displayed in millisiemens, microsiemens, or total dissolved solids.

Toroidal sensors use an inductive two-coil system that’s housed in a plastic case. The coil produces a magnetic field that generates an electric current. The main advantage of this system is that it mitigates the polarizing effects that can lead to inaccurate measurements when using a contacting sensor. You’ll also be able to avoid fouling issues.

Applications of pH and Conductivity Measurements

Many applications can benefit from pH and conductivity measurements, which include everything from water treatment to soil testing.

Industrial Applications

Nearly every industrial application requires a specific pH and conductivity range to ensure the quality of the finished product. For example, boiler feed water makeup usually requires high-quality water that contains few contaminants. This water is used to prevent scale formation and corrosion. Water quality must also be monitored in circulating water systems and cooling towers.

Water Treatment

In the U.S., the water supplies are mostly safe. The tap water that’s sent to residential homes is subject to the EPA’s safe drinking water standards. You can use pH and conductivity sensors to determine if these standards have been met. In the event that there are too many contaminants in the water, it may need to be treated.

With pH and conductivity sensors, you can obtain readings before and after you treat the water, which allows you to identify if the treatments are effective. Keep in mind that tap water supplies can be contaminated by everything from fertilizers and pesticides to sewage releases and naturally occurring chemicals.

Chemical Processing

During chemical processing, you may be tasked with using pH and conductivity sensors to determine the hardness of a solution or to identify the concentration of chloride ions.

Environmental Monitoring

Measuring water quality in the environment is possible with pH and conductivity meters. You can use these meters to determine if a tested sample is hazardous or meets specific standards that the EPA has set. For example, the waters outside an industrial plant can be tested to determine if the facility adhered to EPA guidelines regarding industrial effluent. Once you obtain these readings, you can compare them to the normal contaminant levels in a body of water.

Soil Testing

Soil testing is crucial to optimize crop production and ensure the surrounding environment is protected from contamination. You can also use pH and conductivity measurements to identify issues with plant growth. If you work with your own media, these measurements can help you ascertain soluble salt levels, which is necessary to maintain consistent crop nutrition.

Water Quality Assessment

You can use pH and conductivity meters in your home to perform a water quality assessment. These sensors will tell you if the water is contaminated. If contaminant levels are higher than you’d like them to be, consider installing an under-sink filter. You can also install a large reverse osmosis (RO) filtration system in your home. These systems are powerful enough to remove nearly all contaminants from your water.

Food and Beverage Industry

The food and beverage industry relies on precise pH and conductivity readings to maintain specific tastes and flavors. If low-quality water is used while manufacturing a beverage, it will invariably create a bad taste. There’s also a possibility that consumers will experience health issues, which can include everything from headaches to lead poisoning.

If a plant uses a city’s water supply during the beverage manufacturing process, the water will need to be dechlorinated before it’s used. If two or more production facilities are employed while manufacturing food or beverages, the water supply must maintain consistency to ensure that the final product produces the same flavor profiles and quality in every location.

Brewing

Both pH and conductivity can be highly beneficial when brewing beer or making wine. When you’re brewing beer, pH measurements need to be taken while crushing grains and taking part in the “mashing” process. If you don’t carefully monitor the mash pH, the finished product might have a strange flavor.

When beer is brewed in the correct pH range, you’ll benefit from a more well-rounded flavor profile. If pH measurements are outside the ideal range, several aspects of the brewing process will be negatively impacted. Everything from the sugar conversion to the fermentability of the beer can be damaged.

If you’re using tap water, you’ll likely receive a pH reading that’s higher than 7.0. The grains that are used to brew beer are somewhat acidic, which will cause the mixture’s pH to decrease. If you brew a light-colored beer, additives will need to be applied to the substance to reduce the pH. Since darker grains have more acidity, this extra step won’t be necessary. You need to maintain a mash pH range of 5.2-5.5.

Dairy Processing

During the cheese preparation process, conductivity and pH can be measured while monitoring the souring of the milk as well as the cream maturation. Manufacturers can significantly reduce the growth of bacteria and pathogens by keeping the pH within a range of 4.1-5.3.

Choosing the Right Meter for Your Needs

When you’re searching for high-quality pH and conductivity meters, there are many factors to consider. Make sure you know what application the meter will be used for to ensure you choose the right one.

Factors to Consider When Selecting a pH Meter

Before you select a pH meter for water quality testing, make sure you do your research. Does the pH meter offer portability? If you’re tasked with performing measurements in the field, you’ll need a handheld meter that can be taken with you wherever you go.

It’s also important that you select the right calibration system. High-quality meters are equipped with two-point calibration systems. If you measure a wide pH range, you may require a five-point calibration system.

Consider the electrode as well. This component is responsible for measuring the concentration of hydrogen ions in the water. While most pH sensors are outfitted with glass bulb electrodes, you can’t use them in food measurements.

Keep in mind that more advanced pH meters will come with a temperature compensation feature for times when the sample and pH meter don’t have the same temperature. Look for sensors that have an accuracy ranging from ±0.1 pH to ±0.001 pH.

Factors to Consider When Selecting a Conductivity Meter

When choosing a conductivity meter, there are numerous factors to consider, which include the following:

• Ease of installation
• Primary casing material
• Calibration requirements
• Conductivity measurement range
• Electrode technology type, which can involve contacting and toroidal meters
• Availability of automatic sensing
• Flexibility

Automatic sensing is a modern feature that removes some of the manual requirements that most conductivity meters have. For example, manual sensing means that you’ll need to set the specific measurement range before each application. Meters that contain the automatic sensing feature can detect the conductivity range instantly. You never need to set the range regardless of the application you’re using the meter with.

As for flexibility, the best conductivity meters can be placed in a wide range of different liquids and solutions. Make sure the meter allows you to change the temperature coefficient to accommodate the measured properties. The cell constant should also be adjustable in the meter of your choice.

Tips for Accurate Measurement and Maintenance of the Meters

To maintain accuracy when using pH conductivity meters, you need to adhere to the proper calibration techniques. With pH sensors, use new buffer solutions. You’ll need to wait for the pH values to become stable to complete the calibration.

Whenever you use a conductivity meter, rinse off the solution to ensure the electrode is free of contaminants. If you don’t rinse the meter off after using it, a thin film can develop, which will make the meter less accurate. You can perform conductivity meter calibration by measuring the conductivity of a typical solution and adjusting the sensor reading to match the correct value.

Conclusion

Conductivity and pH measurements play a crucial role in water quality testing. These measurements can tell you how many contaminants are in the water, which should give you the information you need to determine if the solution needs to be treated. You can also use these sensors to identify the types of contaminants that may be present in a substance.

If pH levels are well above 7.0, you can be fairly confident that the substance contains elevated levels of magnesium and calcium. By understanding the relationship between pH and conductivity, you can improve various industrial and municipal processes. Your water treatment techniques should also be more effective at getting rid of contaminants. Use the appropriate meters to gather accurate and reliable measurements.