2-point And 3-point Calibration Comparison For Ph Measurements
To guarantee that your pH sensor is operating properly and giving reliable readings, a number of crucial elements must be in place. Understanding the calibration procedure and how it affects your pH measurement range is the first step in achieving accurate measurements. You anticipate a process to function in accordance with the accepted calibration procedures when calibrating sensors by setting two points on the pH scale. The industry standard for calibrating pH sensors is the 2-point calibration technique. Although single-point and three-point calibrations are less common, each technique has a place in pH measurement. The following will be looked at in this article:
1) Calibration’s contribution to measurement accuracy
2) 2-point and 3-point calibration characteristics
3) When to use each calibration technique
Calibration Basics
For precise measurements, calibrating your sensor is essential. Calibrations can be carried out in a variety of methods by you, your operators, and your professionals. Some ways may be more effective than others depending on the configuration and the process involved.
Understanding a pH sensor’s slope and zero-point is crucial before beginning the calibration process. Each sensor’s values are particular to that sensor. The sensor’s slope is the linear relationship between the pH value and raw voltage (mV) readout. This indicates that in a perfect world, the mV value at pH 7 is zero. Then, as the value changes from pH 7, it should rise or fall by 59.16 mV/per unit of pH.
Unfortunately, there is no perfect world because every sensor is different. Each sensor is calibrated to the slope and zero-point in relation to the theoretical values so that it can account for variations brought on by ageing and process exposure.
Using 2-Point Calibration
The most common and advised calibration technique is 2-point calibration. Many people believe that the more calibration buffers used in a pH measurement application, the more accurate the result will be. This is only occasionally true. Users have discovered that regulated 2-point calibrations may deliver extremely accurate and dependable readings in the majority of applications as industry technology has advanced. The sensor can precisely read the pH of a solution by adjusting your electrode with two particular buffers on the pH scale. We frequently advise performing two-point calibrations using pH buffers 4 and 7, then performing a third-point validation.
Adding a third point to your 2-point calibration allows people used to 3- or multi-point calibration to have further confidence in the sensor’s accuracy. When doing routine maintenance or addressing a particular performance issue, a technician can use a Portavo portable metre that has undergone 3-point calibration in the field. They now have a third source of data to compare to the process reading and lab measurement after obtaining a sample of the process and measuring and data logging with the Portavo. The process measurement may now be quickly and accurately validated without the permanent addition of a third, possibly superfluous variable.
Using 3-Point Calibration
When attempting to cover an even greater pH range, we can use 3-point calibration. As was previously stated, going beyond the two buffer points does not guarantee that a reading would be more accurate. Once more, the majority of 2-point calibrations use the pH 4 and pH 7 suggested buffers.
Users frequently need to set buffers higher on the pH scale for 3-point calibration. Historically, deterioration has been more likely to occur with higher buffers in alkaline ranges. This is especially true when the sensors are subjected to the challenging conditions they work in. This exposure can eventually result in faulty readings and a misalignment of data over time. Such pH data interruption could have a negative impact on costs, time, and output in many of these contexts, including the food and beverage, pharmaceutical, and CIP (clean-in-place) industries, as well as the fertiliser manufacturing process. A 3-point calibration may be required in some applications, particularly those involving processes where values are commonly found to exceed pH 10, in order to cover that wider range.
2-point and 3-point Calibration Summary
Keep in mind that every sensor calibration is specific to the process you are studying. Both the 2-point and 3-point calibration procedures have advantages. But the key to ensuring accuracy is knowing which is preferable for your application. Which method best fits your analysis depends on whether your buffers are applicable to this procedure. For additional details on calibrations and buffers, see our informative films and practical instructions.
