In this video, we will calibrate the EXO NitraLED sensor for nitrate in mg/L. You can also use the EXO Handheld or Kor Mobile App.
Before we begin, I want to make sure that we have our personal protective equipment since this sensor emits UV light. I have my UV-rated safety gloves and my glasses, so I’m ready to go.
Before calibrating, it is important to make sure your sensors, sensor guard, and cal cup are all clean. If you have a wiper installed, make sure that the wiper brush and brush guard are also clean. You should use the NitraLED-specific brush and alignment ring, as well. For best practices, we suggest using a dedicated cup, guard, and wiper brush just for calibration to limit contamination.
Also, make sure you have a calibrated turbidity sensor and Conductivity and temperature sensor installed and functioning in your sonde.
We’ll be performing a 2-point calibration for nitrate. We’re going to use Type 1 water, or DI water, for our first point at 0. If you are using an EXO cal cup, make sure to fill to the first line from the bottom to make sure the sensor tip is fully submerged.
Now let’s immerse the sensor in the DI water. Once immersed, it is extremely important to make sure the sensor lens is free of any air bubbles that could skew the reading. You can do a visual inspection and then tap the sonde to help clear bubbles.
Or, if you have a clean wiper installed, you can activate the wiping mechanism to clear the optical lenses. Just make sure that your wiper is in NitraLED mode. You can set this in the wiper calibration menu. Here, you can see how the wiper operates outside of the solution. The NitraLED brush has an extra brush arm to wipe the optical lenses.
In Kor software, select NitraLED and Calibrate. Now you should see your readings somewhere around zero. Kor will indicate when your readings are stable.
Once they are stable, we’ll go ahead and apply the first calibration point. You will then see the calibration summary, which you can use to double-check the values. So we should see a value of 0 for this calibration result. From here, you have the opportunity to redo the calibration point, complete it, or proceed to the next point.
Now, we’ll dry our sensor and move on to our second point. You need to use YSI’s NitraLED nitrate standard for cal point 2. This standard is filtered specifically for NitraLED calibration. You can select either 5 or 10 mg/L, depending on your preferred range. We’re going to use 5 mg/L today.
Again, we’ll immerse the sensors in the solution and make sure there are no air bubbles on the sensor lens. After stabilization, we’ll apply the cal point. Here again, we can see the calibration summary, and this time we’ll complete the calibration.
The software will ask if you want to proceed to the Site Specific Correction. If you expect high levels of interference due to turbidity and Natural Organic Matter at your site, performing this correction can help improve your data. For more information, please watch our video on performing the Site Specific Correction.
Be sure to check out our other EXO University videos as well, and thank you for watching!