Measure. Analyze. Learn.
This is the Carbon Dioxide Sensor.
It's used in several of our lab manuals;
It shows up in the biology manual, the physiology manual.
And so, it's used to measure the concentration
of carbon dioxide gas.
So, you always want to make sure you are doing a gas.
You don't ever put this into a liquid.
And, the way this sensor operates, it actually uses an
IR detector, and so, it has an infrared source,
that if the CO2 goes through these holes,
the CO2 will absorb some of the infrared radiation
from the detector.
And, the higher the concentration of the CO2 gas
the less infrared makes it to the detector.
Now, since this is using an IR source, you do need to
let it warm up for 90 seconds, when you use it.
So, when you plug it in, at first, it actually, will not give you
a correct reading, until it is ready for collection.
Another thing about that, is that if using this outside,
you would like to avoid having this in direct sunlight,
because you end up warming this up, and you can cause
a change in how the units reading there.
So, you want to avoid that.
Now, this is a dual range sensor.
And so, there is a sensor setting switch here.
So, it's a sensitivity switch.
The low range is a 0 to 10,000 parts per million.
A lot of the experiments will use that.
And then, the higher range is 0 to 100,000 parts per million.
You might need to use that, if you are going to, you know,
breath on it, or something like that.
The sensor in general doesn't need to be calibrated,
but you can, and to do the calibration,
it's important that you put it into a known condition.
Take the Nalgene bottle that comes with it,
and you could collect a sample of air,
and it has a lid that you can put on it.
And, you could bring it back in and do the
calibration that way if you wanted to.
There is a calibration port right here.
And, you can take, maybe, a paper clip,
and press down on this until it, the unit, stabilizes.
It will end up with a reading of 380 parts per million.
Then we assume that's what it is outside, in open air.
And then, you're good to go.
To use this, we suggest that you would use it with
several different chambers that we have.
I just mentioned this Nalgene bottle.
This is the one that comes with it.
Another option is to use this BioChamber 250.
And, this allows you to put more than one sensor in,
if you would like. So, you could put a CO2,
and maybe an oxygen sensor in there. So, you can use that one.
In addition to that, we have the BioChamber 2000.
And, it allows us to put two sensors in a container.
And so, it has two holes, so we could put a CO2 sensor here,
maybe an oxygen sensor there,
and measure both of those two things simultaneously.
Again, you might use this with labs like the respiration of peas.
It's one I'm going to use here.
You could use it with, maybe put some crickets,
or worms in there, and look at their respiration rate.
Fermentation of yeast; so you're producing CO2
from the fermentation. You might use it that way.
Some chemical reactions that generate CO2 gas.
And so, anything that is generating the CO2 gas,
you would use this device.
So now, were ready to, maybe, collect a little data.
And, we need to plug in the CO2 sensor to our LabQuest.
And so, I'm going to plug it in here.
And so it's, once it goes in, right now the device is
reading 0 parts per million.
And, we said it need to warm up.
And, it will continue to give us a reading like that,
until it is warmed up.
And so, that takes about 90 seconds for that to warm up.
And, I want to make sure that I have this
on that lower range setting there.
While that's warming up, what I'm going to do is take my peas;
and these are some peas that I started soaking
a couple of days ago. There actually sprouting at this point.
And so, there probably producing a lot of CO2.
And, I'm going to place them into my bottle there.
There's about 25, or so, peas there.
And so, I'll just put those there.
And now, there we go. So our unit is now reading here.
And so, inside our room here, we've got about
600-and-something parts per million.
So, if we look at our collection parameters
in the upper right corner here; we see 'Time Based';
meaning that it is a variable is as a function of time;
so, CO2 concentration with time.
The default rate is .25 samples per second.
So actually, every 4 seconds it's going to make a measurement.
It can go faster than that, but because we're measuring
the CO2 that has to diffuse through these holes,
it may not change all that rapidly.
So, collecting data faster than, say, four points per second,
you really don't have to do that.
And, you end up generating more,
maybe more, data than you want, to be able to do that.
So, you need to allow time for that CO2
to make it into the sensor there.
And then, if we look at our default time for this.
It actually is a 600 seconds, so it's a 10 minute.
And, that's fine for a lot of experiments.
And, in fact, for this one we'll just use that
as our default setting here.
So, I've put my peas into my bottle,
and I want to put the sensor into here.
One suggestion that we have here, is that you actually run
the experiment on its side here, because that CO2 gas is heavy.
It tends to form a layer down towards the bottom
of the container, and if you do it upright, it may take
longer time for it to diffuse, and you end up with
a kind of layering effect there.
And so, once we've done this, we're ready to collect the data.
And, to begin collection, all we need to do is press
the collect button. And, we press collect.
And, it's now going to collect for 10 minutes.
And, we'll watch what happens to the concentration
of the gas in the container.
So, we've finished our data collection.
And, it looks like our CO2 level was increasing nicely there.
And, we might want to run some analysis here.
So, it looks like our CO2 was increasing fairly constantly there.
So, why don't we run a curve fit,
and maybe look at something about the rate.
So, I'm going to go to 'Analyze'.
And, I'm going to go down to where it says 'Curve Fit'.
And, I will check the box next to 'CO2'.
And so now, I need to, maybe, try my equation here.
It looks linear to me, so I'm going to try a 'Linear' fit.
And, there we get our fit.
And I will say 'OK'.
And, it looks like it fits nicely, and we have a slope there of
4.4 parts per million per second, there.
So, it's increasing at a constant rate.
So again, this sensor is used widely for biology and
biology related experiments.
It's definitely a good one to have.
And, it allows you to measure things that would be
very difficult to do other ways.