Par Sensor - Tech tips with vernier

Hello, I'm John Melville from Vernier Software & Technology. I'm here today to talk to you about our PAR sensor. Now, a PAR sensor is effectively a light sensor that responds to the wavelengths of light that plants use for photosynthesis. And that's different than a standard light sensor. A standard light sensor that you might be used to really responds primarily to the wavelengths that we see the best, which is green light. And plants don't use green light for photosynthesis; they use predominantly blue light and red light. Now, a PAR sensor is designed to respond equally to all wavelengths of light from 400 to 700 nanometers. What I'm going to do now is I'm going to connect our PAR sensor. This is the sensor head. There's a little amplifier box. And then this is the BTA end of the cable that I'm going to plug into the LabQuest 2. Now if you look over at the LabQuest, what you can see is that it's reporting the amount of light in micromoles per meter squared per second. And this is commonly referred to as PPFD, or PPF, and that stands for photosynthetic photon flux, which is basically just a fancy word for saying how much photosynthetically active radiation is falling over a given area. And what I want to show you is that this PAR sensor is much more sensitive to wavelengths of light that plants use for photosynthesis. What I have in this lamp right here is a standard 25-watt incandescent bulb, which might look relatively bright to you, but it doesn't have a lot of blue light in it and it's not going to be able to drive photosynthesis very well. It's not what you would want to use to put over your plant to help it grow. What I have over here is a halogen lamp, and a halogen lamp has much more blue light and its PAR value is going to be much higher. And I can just demonstrate that very quickly by taking the PAR sensor here and I'm going to place it... underneath the incandescent lamp. And you can see that it's reading about 35 PPFD. And now I'm going to take the PAR sensor and place it under the halogen lamp. And you can see in this case it's reading around 200 PPFD, so quite a bit more. Now, this sensor can also be submerged. So this cable that I'm showing you right here is just under 5 meters long up to the end of the amplifier box, so I can submerge this entire cable in water. Now, I don't have a lake or a pond to submerge it in, but I just want to show you that I can submerge it and I won't damage it at all. So I'm going to submerge it here, and there, I can actually put the cable all the way up almost to the end of the sensor box, and it doesn't damage the sensor at all. It's an excellent sensor if you want to do any experiment that looks at photosynthesis or primary productivity. And that's all I have to show you about the PAR sensor. Fore more information about the PAR sensor or other sensors from Vernier Software & Technology, visit us online at www.vernier.com.