While direct measurement of ammonia is one of the most popular ion selective electrode (ISE) measurements performed today, it is also one of the most challenging. This technical bulletin will discuss many of the most common problems and offer suggestions to overcome these difficulties.

The average person thinks of viscosity as how thick a liquid is, such as when waiting for ketchup to come out of the bottle. Of course, temperature affects the flow of ketchup. At room temperature, ketchup flows much easier than when it is right out of the refrigerator.

However, the more correct definition is this: viscosity is a measure of a fluid’s resistance to flow, or more precisely, it is the ratio of the force required to overcome internal friction between layers of fluid (shearing stress) to the change in speed between layers of fluid (velocity gradient).

Industrial and municipal wastewater needs to be treated before it re-enters our lakes, canals and rivers. Extreme pH levels, particulates, toxic contaminants, and high levels of alkalinity are common problems in wastewater. Wastewater treatment is a serious environmental concern. The use of pH in the treatment of wastewater requires a quick, accurate and robust measurement.

Commercial and recreational gardeners are showing a growing interest in taking accurate pH measurement of soil samples. The pH of soil indicates more than its alkalinity or acidity strength; it affects the relative availability of nutrients, the soil life, and the type of plants that will thrive.

The common range of soil pH varies from 4.0 to 8.0; the range of soil pH for optimal availability of plant nutrients is 6.0 to 7.0. The ability of soil to provide adequate nutrition to the plant depends upon the following factors:

Some consider moisture determination a dry subject. Yet, for food and pharmaceutical manufacturers, cosmetics producers, and others seeking to ensure consistent uniformity through each stage of production, moisture determination is a necessary step in product quality. The moisture content can reveal properties of the material relative to purity, concentration, stability, shelf life, and nutritional value.

Frontline mechanical maintenance teams need:

• A quick screening tool to fit into existing rounds.

• Reliable and repeatable measurements of rotating equipment to make imperative go/no-go maintenance decisions.

• Ability to trend readings over time and notify a consultant or reliability engineer when something abnormal arises.

• Quick understanding of overall machine and bearing condition, to decide on repairs and repair equipment.

“What could possibly be so difficult about reading the pH of pure water? It should be neutral pH 7.0, and there are no interferences,” common sense says. In practice, it can be quite difficult and often frustrating to obtain reproducible pH values in samples with low-ionic strength. Water that has very few ionic species is said to be low in alkalinity, ionic strength, or have low conductivity/high resistivity such as distilled or deionized (DI) water. It is common to attain different pH values with new, sealed electrodes that calibrate perfectly in pH buffers when attempting to measure DI water. This is due to the varying junction potentials that develop across the reference junction. Some techniques and product recommendations for overcoming such limitations will be discussed here.

Yogurt is a popular dairy product made from concentrated milk fermentation. The quality of the product depends on production control of lactic acid formed by fermentation. Lactic acid provides the tart flavor and the destabilization of milk protein forms the gel structure. pH measurement monitors lactic acid production and aids in the quality control of yogurt’s ingredients.

Chemical Inc., a chemical manufacturer, is losing raw materials to what they thought were erroneous pH readings. They have a pH control system in place that activates a solenoid valve in the bottom of the tank once a specific pH is reached. Shortly after the tank started emptying, they saw the pH spike and manually shut off the valve and scrapped the batch. After this occurred a couple of times, they began rechecking the pH of the raw material and found it was exactly where it was supposed to be. They even double checked it with a separate tester. So, they asked for a warranty replacement on the pH probe. Upon troubleshooting, it was determined the solenoid valve was starting to go bad. As the valve wore out, stray electrical signals entered the mixing tank and the pH probe interpreted the stray signal as a change in pH.

What should the team use to avoid erroneous readings from stray voltages in the future?

A. An air-actuated ball valve (such as 01347-74) to avoid stray electrical signals

B. A solution-grounded pH probe (such as 27018-00) to combat electrical interference

C. A high-accuracy fast-response pH probe (such as 27040-02) to read quickly before any electrical noise can interfere

D. A new solenoid valve overall (such as 98604-50) since the issue was the old solenoid valve

Answers:

A. An air-actuated ball valve (such as 01347-74) to avoid stray electrical signals 
Incorrect. This would require that the pH controller is set up to activate an air compressor. More engineering would need to go into putting an air supply line in place along with the compressor.

B. A solution-grounded pH probe (such as 27018-00) to combat electrical interference
Correct! Addition of a ground wire would allow any stray electrical signals in the solution to go to the grounding wire rather than the pH probe itself, eliminating any unstable or inaccurate readings.

C. A high-accuracy fast-response pH probe (such as 27040-02) to read quickly before any electrical noise can interfere
Incorrect. The fast response time of this probe would make electrical noise and provide jumpier readings.

D. A new solenoid valve overall (such as 98604-50) since the issue was the old solenoid valve
Incorrect. Although Chemical Inc. may want to replace the solenoid also, there is a better solution. Additionally, we are unsure of chemical compatibility and this is only a PVC and EPDM valve.