Hello, my name is Ben Crabb.
I do technical sales and support here at Apogee Instruments.
I’m here to talk about a tool that we put together to help our users of quantum (or PAR)
sensors to get more accurate measurements under a variety of lighting sources and correct
for the spectral errors that may occur.
Let’s do a little examination of the quantum sensors that Apogee carries.
We carry two basic varieties of quantum sensors: our original quantums and our full-spectrum quantums.
The originals came out a number of years ago.
They are a low cost option that produce very accurate measurements under broad spectrum lights.
Their spectral response drops off a little bit in the red range and the blue range, but
they are an excellent choice for most lighting conditions.
The tool that we’ll go over momentarily is most applicable to these original quantums.
The full-spectrum quantum has a response that more closely approximates the PAR response,
which is 400 to 700 nm, which has been defined as the wavelengths of light that plants can
use for photosynthesis.
So this is a look at the spectral responses of those two types of quantum sensors,
as well as the PAR response.
The PAR response being shown by this black dotted line.
And the original quantum response being the thick black line.
You can see it drops off in the red range out here from 655 to 700, and it drops off
a little bit in the blue range as well.
So if your light emits a lot of light in those portions of the spectrum, the original quantum
is going to read a little bit low, erroneously low.
The full-spectrum spectral response is indicated by this gold line.
You can see that it nearly approximates, very nicely approximates, the dashed black line
of the official PAR response, and so it’s going to provide very accurate measurements under
any lighting conditions.
Let’s move to the tool.
Here is the page for the tool, and we will include the URL in the comments section down below.
Let’s scroll down and examine it.
It’s pretty easy to use.
The way it works is you just select your sensor and your light source and this display will update.
The green line indicates the spectral response of the sensor, the red line indicates the
output of the light, and the black dashed line indicates the official, or the defined,
PAR response, which is 400 to 700 nm.
And so as we select the different sensor options, we have two different original quantums.
One’s been calibrated to read most accurately under sun; the others been calibrated to read
most accurately under T5 lights.
And then we have our SQ-500, which is one of our full-spectrum quantum sensors.
It’s going to read accurately under any lighting conditions.
So, as an example, what we have selected here is “clear, sunny” day.
This is the lighting spectrum that would be expected on a clear, sunny day.
And we see that our sun calibrated SQ-110 original quantum sensor the expected error
on this guy (let’s unclick this) our expected error on this guy is 0 % and the correction
factor being 1.00.
That just means you take your reading from your SQ-110, you multiply it by the correction
factor, in this case it’s 1.00, and you get a more accurate PAR reading.
Of course in this particular instance, multiplying by 1 you get the same reading because it’s
already very accurate.
But if you had used this electric calibrated sensor, original quantum sensor, it’s the
same sensing technology but it’s been calibrated to read accurately under T5 lights.
Now you take it out in full sun, you measure PAR, and you get a reading that is about
14 % lower than it should be.
So the tool says to apply a correction factor of 1.16.
So you take your reading from your SQ-120, you multiply it by 1.16, and you get a much
more accurate PAR reading.
And so that’s the way the tool works, and you can scroll through the different preloaded
lighting spectra we have in this tool.
You can use the arrow keys on your keyboard to go through it quickly if you like.
This little rectangle up here will be color-coded yellow if the error is between 5 and 10 % and
red if it’s expected to be more than 10 %, and it will show those correction factors.
One thing to note is that with LEDs, which emit a lot of their light in very narrow spectral
ranges, if you use a deep red LED, so the one we have displayed here is a deep red LED
with a 668 nm peak.
Now this is outside the range of highest spectral sensitivity of the original quantums.
So the original quantum sensor doesn’t pick up much of that light very effectively, and
so it’s reading, I mean this one says the expected error is negative 65 %, so it’s
going to be very low.
And you can apply that correction factor, but do it with caution because if the sensor
is not detecting much of the light, and you try to correct that, you may not get a really
reliable reading.
You’ll be better to get a higher quality sensor such as the full-spectrum quantum.
A couple other things to note on this tool is we have this check box down here to show
correction factor for underwater measurements.
It’s useful for people who like to measure PAR in their aquariums for corals and such.
When you select this, the display will update and it will show the expected error in air
and the expected error in water and correction factors for both situations.
So that’s how that works.
And then we a final functionality of this tool.
You can upload your own custom lighting spectra, or if you don’t find your lights on the
list here, or you know the spectra of your light is different than what we have loaded
here, you can upload your own data.
You just click this browser button and you navigate to the .csv file on your machine.
It expects the first column to be wavelength expressed in nanometers and the second column
to be light output.
And when you do that then you just select the custom data from .csv file under the light
source, and that display will update.
In this case we haven’t uploaded any light data, and so it says to upload some data.
Anyway, what else do we have?
… I think that’s all we have.
This tool is under development.
We welcome any feedback.
This is our email address and our phone number.
Please leave any comments down below, and please subscribe to our Youtube channel for
more updates from Apogee Instruments.
Thanks for watching.