Measure. Analyze. Learn.
Hello, I'm John Melville.
And, I'm here to talk to you today about our new Ethanol Sensor.
Now, this is a little ethanol gas sensor, that basically can
be used to measure ethanol gas in a vapor above water.
It's not designed to be put into water, or any solution.
It's really only designed to be used to
measure ethanol vapor, ethanol gas.
It has a limited range, it only goes from 0 to 3 percent.
And, you actually need to protect the sensor element,
using a little piece of Teflon tape.
And, this will just make it last a lot longer,
so that it won't get wet, since you are going to be
putting it above a solution.
So, just in case it does fall into the solution,
you won't destroy the sensor.
To apply the Teflon tape, all you need to do is:
break off a little piece of Teflon tape;
and this Teflon tape is supplied with the sensor;
you then remove the cap from the sensor;
place the Teflon tape over the sensor;
and then, gently push the cap back on to the sensor.
And, if you wanted to, you could trim the excess Teflon tape.
And now, you're ready to go.
This sensor itself, does take about 5 minutes,
5 or 6 minutes to warm up.
I've already connected it to my LabQuest.
And, you can see it's reading about 0.017 percent ethanol.
It will never read absolutely zero.
That's because of the type of calibration that's used.
We're using a power calibration.
You will never see absolutely zero on the ethanol sensor.
This sensors really designed to be used to monitor
things like fermentation, that's really what it's best for.
And, that's actually what I'm going to show you next,
is how to use this CO2 sensor, and this ethanol sensor
to monitor fermentation.
Now, you can calibrate the Ethanol Sensor if you want to,
but you shouldn't need to for an experiment like this;
fermentation.
If you actually wanted to measure the
absolute concentration of an ethanol solution, you could,
but you would need to do a two point calibration.
You would need to make two solutions of ethanol,
and you would need to actually tell the Ethanol Sensor,
this is 1 percent, or this is 3 percent,
or this is 0.1 percent, or 1 percent.
All of those instructions on how to calibrate it,
can be found in the users manual,
or what we call the sensor booklet.
But, like I said, for most experiments that biology teachers
are going to want to do, you don't need to calibrate the device,
you just need to plug it into the LabQuest,
wait 5 minutes, and then you're ready to go.
Now, the sensor itself also comes with, what we call,
a little fermentation chamber, or a Nalgene bottle.
It comes with a lot of Teflon tape,
so that you can do a lot of experiments.
It comes with a spare cap,
just in case your student lose the original cap.
And, it also comes with this really nice little stopper.
And, the stopper is designed to be put in
the top of this chamber.
And, it's also designed to be put in the
grommet that you find in our large bio chamber.
So, you can place that right in there.
And later, I can take the Ethanol Sensor
and place it down into the chamber here.
So, let me just show you how to set up a
very simple fermentation experiment.
You just need to fill up this large bio chamber with
amount of water; it needs to be a little bit warm;
so that it comes to the very bottom of this red mark, right there.
And then, all that I'm going to do is, I'm going to take the top off.
Now the reason why I have it on a stir station is because,
that is going to disperse the ethanol that's being produced
by the yeast into the air pockets that are there.
And, it will respond a lot faster.
Everything is going to work for you much faster if you
actually use a stir station, and a stir bar,
if you want to look at fermentation rates.
So, I'm going to supply our yeast with a little bit of sugar.
This is just simple table sugar, or sucrose.
I'll put some in there.
Get a little bit more table sugar.
I'm just going to dust that off there.
I can mix it up a little bit.
There we go, that's spinning nicely.
Now, I'm just going to add just a little bit of yeast.
And, you don't need to add a lot of yeast.
You could add a {whole pocket}, a whole packet of yeast
if you wanted to,
but you really just need to dust the top very lightly.
So, I'm just going to just sprinkle some yeast to cover the top.
Let those yeast get going.
Now, I'm going to put this top back on.
Then, I'm going to place the CO2 sensor into the chamber.
Now remember, this is a gas sensor, I don't want to get it wet.
So, I want the top right here, not to touch the water,
but to be just above it.
So, I'm going to place it down into here.
And that's why if you actually just fill the level of water to
this little red line right here, that you see right here,
you should be fine.
The CO2 sensor can't be dunked into the water
if you just fill it to the bottom of that red mark.
Next, I'm going to take the ethanol sensor,
and I'm going to take the ethanol sensor,
and put it inside of this little stopper, like that.
And then, I'm going to place the stopper into the grommet,
and twist it, so it's tight.
And then, I'm going to place this close to the water level.
And really now, the only thing I'm going to do is,
I'm just going to change the units.
I like to have the same units for CO2 and ethanol.
You don't have to do that on the LabQuest,
but I like having them both read in ppm.
So, I'm just going to tap on the meter where it says ethanol,
and I'm going to change my units to "ppm".
And then, if you wanted to, you could begin recording right now.
Normally, it would be best to wait just about 2 or 3 minutes.
But, I have this whole file set up to record for 10 minutes,
so why don't I just hit collect now,
and we'll see what happens over the next 10 minutes.
So, you can see right now, it's been about, just over 5 minutes,
and we're getting to the maximum amount that
the CO2 sensor can take, which at the low setting,
which is about 10,000 ppm.
So, I'm going to stop it.
Now, if you wanted to, you could always take
the CO2 sensor and put it on the high setting,
but you get a much cleaner response if it's
actually on the low setting for yeast.
And really, what you're trying to see when you're looking
at fermentation, is that yeast can take sugars,
and they turn that into carbon dioxide gas and ethanol.
And you can see that right here on this graph,
that we have a production of ethanol over time,
and a production of carbon dioxide over time.
And, if we wanted to, we could look at the rate of
ethanol production, and CO2 production over time.
Now, the other thing I wanted to let you know is that
this ethanol sensor can respond to other chemicals
besides ethanol. It's also not temperature compensated,
and it's not pressure compensated.
So, we really are using this ethanol sensor to
just demonstrate that ethanol is
produced by yeast during fermentation.
So, let's just take a quick look and find the rate
of production of both of these gases.
So, if I tap on the graph, and drag across,
that's a nice little region where I can see it's increasing.
I can just tap on "Analyze", and I can select "Curve Fit",
and then I can pick either one that I want.
I can pick "Ethanol".
And then, I'm going to chose "Linear".
And you can see that the slope there is about .67.
And then, I could do the same thing for the CO2.
I just go back to "Analyze" - "Curve Fit" - select "CO2",
pick my "Fit", which for most
things that we do in biology is going to be "Linear".
And you can see it's about, the slope's about 22.
And, that is a very simple demonstration of
how you can use our Ethanol Sensor,
and our Carbon Dioxide Gas Sensor,
to look at fermentation with yeast.
If you have any other questions about cellular respiration,
or fermentation, or CO2 sensors, or the Ethanol Sensor,
just go to our website at www.vernier.com.