In this video, we'll be calibrating the EXO pH sensor using Kor Software. You can also use the EXO Handheld or the Kor Mobile App.
An accurate pH reading relies heavily on temperature, so be sure to have an EXO Conductivity/Temperature sensor installed as well.
Before calibrating, it is important to make sure your sensors, sensor guard, and cal cup are all clean. And if you have a wiper installed, make sure that the wiper brush and brush guard are also clean.
For best practices, we suggest using a dedicated cal cup and guard just for calibration.
I also recommend taking the bottom plate off the guard to minimize the risk of transferring liquid between buffers!
We recommend doing at least a 2-point calibration with pH 7 as the first point and the second point either 4 or 10, depending on your expected field measurements. For the purposes of this video, we’ll be conducting a full 3-point calibration.
When calibrating pH, you always want to use fresh and traceable calibration solutions. We don’t want to introduce unnecessary errors by using contaminated or inaccurate buffers.
If you are using an EXO cal cup, make sure you fill to the first line from the bottom to ensure that the pH sensor tip and temperature sensor are submerged.
Now let’s immerse the sensor in the pH 7 buffer. Once immersed, I like to move the sonde around and give it a few taps to make sure there are no air bubbles trapped around the pH bulb.
Kor software will indicate when your readings are stable, and you can see the actual pH millivolt readings in real time. You want to make sure both pH and temperature readings are stable before proceeding.
While we’re waiting, let’s take a moment to discuss pH millivolt readings, which is the raw signal that can be used to judge the performance and understand when the sensor module needs replaced. For a functional pH module, the pH millivolts should be reading close to zero, + or - 50, in a fresh 7 buffer.
Once the readings are stable, we’ll click apply. You will then see the calibration summary in order to double-check the calibration values. From here, you have the opportunity to redo the calibration point, complete it, or proceed with the next point. Click to add another cal point.
We’ll rinse off our sensor with DI water and move on to the next point.
Here you can choose pH 4 or 10; the order really doesn’t matter. Let’s go with 10 for this video.
Again, we’ll immerse the sensors in the solution and give them a few taps. In 10 buffer, we should see millivolts stabilize close to 165 to 180 less than the millivolt value in buffer 7, so we are looking for a negative slope.
Please be aware that it can take a minute or two for pH readings to stabilize. For our purposes here, we've sped up the video.
After stabilization, we’ll apply the cal point. Click to add another cal point. Now we’ll rinse and move on to the final cal point.
Now we’ll immerse the sensors in the pH 4 buffer. Give it a few taps, and wait for stabilization. We should see a pH millivolt reading of 165 to 180 greater than the millivolt value in buffer 7. Once stable, we’ll click Apply. Now we’ll complete the calibration. We can see the calibration summary. Our millivolt slope is shown for pH 7 to 10 and 7 to 4. In both cases, we should see a change between 165 and 180.
Our pH sensor is now calibrated and ready for use. Be sure to check out our other EXO University videos, and thanks for watching!