- Today I'm going to talk about the Vernier Turbidity Sensor and using it with
our LabQuest 2. The Vernier Turbidity Sensor is often used with water quality
measurements to be able to measure the amount of turbidity that is in a water
sample. Turbidity is looking at how cloudy that water sample is, and how many
particulates are actually suspended, giving us an idea of how clean or what the
quality of that water sample is. The turbidity units its measured in are NTUs,
or nephelometric turbidity units, which is a national standard. So, first what we
have to do with our turbidity sensor, is to connect it to our LabQuest 2. Now, once
the turbidity sensor is connected to the LabQuest 2, if you have a very, very clear
sample of water that you're measuring, you're going to want to let it warm up for
about five minutes. If your sample of water is more turbid or a lot cloudier,
you will not need to let it warm up for that long. So first what I need to do is
actually calibrate my sensor. So to calibrate your turbidity sensor, the
sensor comes with a 100 NTU calibration standard. So this is going to be our first
calibration point. Then you're going to need to use the cuvette that comes with
the sample and fill that with distilled water for your second calibration point.
In order to do the calibration, first we're going to tap on our meter screen and
enter the calibration screen, and then tap calibrate now. The first one we're going
to measure is our 100 NTU sample. What I want to do is actually gently invert
this about four times to make sure that the standard is evenly distributed.
Now, I don't want to shake it because then I could introduce bubbles into the sample.
That could affect its reading. So I might have touched the outside of my vial and
want to remove any fingerprints with a lint free cloth. So I wipe the vial with
the cloth. Then I'm going to place the vial into the turbidity sensor. I want
to make sure that the arrow on my sample vial lines up with the arrow inside my
turbidity sensor. So I'm going to line those two arrows up as I insert my sample,
close my lid, wait for my voltage to stabilize, and then enter 100 as my known
value. Now, my second known value is going to be a zero, which is with my distilled
water. So I've taken our empty vial that comes with the sensor, filled it up just
above that line so the meniscus is touching the top of the white line on the
bottle. Again, we want to wipe off our vial to remove any lingering fingerprints.
Then, place the vial, again, into the turbidity sensor, lining up the arrow on
the vial to the arrow inside the turbidity sensor. Close the lid, and wait for my
voltage to stabilize. Once my voltage has stabilized, I'm going to select zero as my
known value, and then keep. Now often, this measurement is actually going to be
done within a field environment. So it's recommended that if you're going to do
calibration, to calibrate in the classroom or lab before you enter the field.
Then, what you can do is actually store your calibration to the sensor itself
so that the calibration is remembered when you go out into the field.
So to do that, on our same calibration screen, we're going to select storage,
save calibration to sensor, select OK, and then select OK again. Now, that
calibration is going to be remembered with that sensor so that you don't have to do
it again in the field. In order to do a sample measurement, the thing to remember
is one, if you're in the field you want to make sure that your turbidity sensor is on
a flat stable surface, that way it ensures an accurate measurement. Again, with our
sample, just like we did with our blank standard, we want to be able to fill the
water line sample up to above the line where the meniscus is touching just the
top of it. This sample, I took from one of our many aquariums that we have here,
and it's been sitting for a little while. So again, I'm going to invert it a few
times to distribute the particulates. I'm also going to use a lint-free cloth to
actually wipe off my fingerprints that are on the bottle. And again, remember, do
not shake because you'll get bubbles within the sample. So I'm going to line up
again the arrow here with the arrow inside of the turbidity sensor. Then I'm going to
take a reading almost immediately, because once the sample sits,
all the particulates are going to start settling to the bottom, affecting my
reading, and giving me an inaccurate value. If you have any other questions
about the turbidity sensor or any of our other sensors, please visit our website.