This Acrylic Calibration stick is used to confirm that your meter keeps the specification it arrived with and keeps them throughout the usage of the meter. This is a reusable tool, you’ll need to check your meter as you receive it, with this key. Simply put the key into the cell and test; make sure to keep hold of that test result as next time to test it to check if your meter is still well calibrated, you’ll need to compare the results.
Always make sure the that the cell is clean and the meter and batteries are in good working order before you use the calibration key.
If the results are within the desired range then you can be confident that the photometer is calibrated and that you are performing the tests correctly.