 The professional would properly calibrate it every day before we go out to the field. And pH is important, the basic cleaning steps, we want to wash the probe with distilled water and the container cup. I'm going to take out the sponge, since we don't need it anymore. That's just to keep the probe from being damaged, keep the environment moist and rinse out the cup. And we have two standards that we're going to be testing. One is pH 7, which is yellow, and the second one is going to be pH 10, which is blue. And so it's important to know what water you're testing. Because most of the range of the water we were testing on the field was between 68, actually. So we're going to take a little bit of pH 7, put it in the container cup, rinse it with a probe, and ideally you want to do this three times, trying to make sure that the bubbles are all out of the container, otherwise it will affect your readings. Now we want to fill the cup just enough so it covers the bulb of the pH meter, the bulb and the holes right over there. Our meter is going to show the run screen, and we want to calibrate instead. We're going to go down and select IC2 pH, that's where our port is at. And now we want to record what we see. Our calibration value is reading at 7.01, which is good. Accept that calibration, we'll press enter, and it will say press cal to finish or press escape to board. We don't want to do that now, what we want to do is record, again, the actual readings, post calibration, which shows ready for point two. Accept calibration, again it will ask us for press cal to finish, press escape to abort, or ready for point three, which we're not. Now we want to validate our meter. So now we have pH buffer of 7, and again you want to pour enough solution so that you can cover the bulb as well as the hole. So we're showing you the pH of 7, and if this is an actual sample, we can actually just start recording. So we'll press enter and start logging, and it will keep logging until I actually press stop. Let's take our probe out, again, rinsing our probes to keep it clean, now that I no longer need the probe, I'm going to replace the sponge in the container. We'll secure the cup to the container, and now we can power down our device. The reason why we want to calibrate to pH for the meter is it's part of the SOP, you'll need to check it at least a minimum of twice a day. One, the beginning of your shift, and ideally at the end of the shift, and once you're out in the field, having a proper calibrated pH meter on this machine is important, so it will provide you much more accurate results. Some of the water, as I said before, we're going to be testing pH between a range of 68, and pH is important for aquatic and biotic organisms, or fresh water. I want to test for ion concentration as well, so there are more metals inside the water body. It would show up on the meter as being a high acid range, which would be toxic to some form of life.