pH sensors may be designed for accuracy, but there are numerous influences on accuracy that go beyond design. Materials of construction, junction types, and measurement ranges are all integral to maintaining accuracy. However, process variables like temperature, chemical reactions, and seemingly innocuous factors like sensor orientation all contribute to the reliability of a process’s accuracy.
While these examples are common, even glaring points on maintaining accuracy, there’s also an abundance of other factors that affect accuracy that may not be so obvious. Let’s start the new year feeling mindful by taking a look at some lesser known variables to consider when prioritizing accuracy for industrial measurements.
Ground Loops/Electrical Interference
This issue is especially severe in plants with high-power electrical systems or welding equipment. Proper grounding, shielding, and signal isolation are critical to maintaining accurate measurements in such environments. pH sensors generate millivolt signals that are sensitive to electrical interference. Without accounting for signal isolation, these stray interferences can cause interruptions to accurate measurements.
Storage
Sensor and buffer storage may seem like an innocuous factor on accuracy. However, proper storage of these materials goes a long way in their longevity. Storing a pH sensor dry causes the hydration layer to collapse, leading to sluggish response and offset errors. Freezing conditions can crack the glass or displace electrolyte. Storing in deionized water leaches ions and weakens the reference system. Ensuring sensors are stored properly with a wetting cap, and that buffers are tightly sealed to avoid contamination, are simple but necessary steps to take towards reliability.
Micro-fractures
Though glass pH sensors are essentially standard and intrinsically robust, they are still vulnerable to micro-fractures. These fractures are not immediately visible to the naked eye. Rapid increases in pressure and extreme temperatures beyond a sensor’s specifications can cause these fractures, harming the measurement’s integrity. Glass impedance diagnostic capabilities like those of the Stratos Multi can help catch such abrasions early to avoid downtime.
Improper Cleaning Materials
Aggressive cleaning chemicals can attack the glass membrane or dissolve sealing materials. Certain chemicals may etch the sensor’s glass, causing direct harm to it’s functionality. Repeated use of incompatible cleaning solutions shortens electrode lifespan and introduces calibration drift. Following manufacturer-recommended cleaning agents and concentrations preserves sensor accuracy.
Polarization
Electrode polarization occurs when electrical currents pass continuously through the pH electrode. Over time, this creates charge buildup at the electrode interface, altering its potential. This effect mimics an aging electrode, which may lead to unnecessary expenses in replacements. Routine calibrations and signal shielding are reliable methods to ensure polarization is avoided.
Keeping pH Sensor Accuracy on Track
There’s an almost overwhelming number of factors that can impact industrial measurements. Knick’s Memosens sensors are designed with these factors in mind. Staying mindful of calibrations, storage, and cleaning are the foremost methods of maintaining accuracy. Want to know more about maintaining maximum accurate uptime? Schedule a training with M4 Knick to get the most out of your solutions.