Hey People,

I will be writing up in more detail the nutrient requirements of plants, simple overview with a list and a few references/useful links. And another one on the UV technique later in the week.

Shabaz, would you mind writing a quick summary of the inductance measurments, pro's cons and a few links to one in action. To give the rest of us a litle intro into it because I'm guessing we are all new to this. And anyone with some spare time, any input would be great, maybe lets concentrate on techniques rather than implementation this first week?

I actually tried to make a slit over the weekend when I had half an hour, here was my quick attempt:

It is basically two scalpel blades with the sharp ends close together. Behind the blades is a large (8mm dia) hole.

Here is the view from the other side:

I just finger-tightened the nuts, and then manually adjusted the blades until they almost touched. However, it wasn't great. Probably razor blades have a much better defined edge.

Anyway, it seemed to work. This was the setup - I just used a keychain LED light as a test source light.

I manually held the diffraction grating over the slit (about 1 inch apart) and took a photo with the other hand, excuse the blurriness:

The colors from the white LED are easily visible.

So, it would appear it is not hard to get some output, not optimal but works.

By the way I tried to repeat with the DVD-R, but I got nothing like this level of output. So maybe the Edmund Optics kit is worth obtaining just to make life easier.

What is the size of the gap you aimed for when you closed the gap between the blades?

Hair-width, anything around 40-100um. Basically by holding it to a light, the gap should be visible, but about paper thickness or less. It is possible to eye-ball it and get the slit parallel to 20um I reckon..

I did try holding small piece of tape at the end (not the center, otherwise it messes up the sharpness of the edge) and then at the other end, alternating until the gap was perfect. That kind-of worked, but the scalpel edge was not perfectly straight. I think razor blades will be more accurately cut.

So we would need to be changing these blades every so often to stop corrosion changing the sharpness of the slit. something we could live with. Great start!

We should have a decent list of what we need to measure and what we would like to measure soon, just cutting a few papers down into a readable chunk tonight.

Hi Michael,

the problems of the blades oxidation exists. This is a valid solution also adopted by some professional analysis devices but the blades are to be considered as spare parts (or using nobile metals like Platinum but I suggest not ) Then AFAIK from a previous life as chemistry, I suggest to make a blade support for the more standard cutter blades that cost few $ per pack and replace them periodically. Also when oxidation starts the first thing that is attached is the thickness part and the results can be altered by small blade discontinuities. I think that in this way the solution will work perfectly, expecting for an almost continuous usage a blade replacement every 1-2 weeks.

Enrico

Yes, I have been waiting for a good discussion on spectroscopy.

For crop health information, you can do a lot of processing with just RGB photographs, but adding a good IR image can greatly expand the information content.

I hope to get to providing some good articles on these issues over time, but it looks like we have a good exchange of information already.

DAB

I've just added a bit of a write up for what we need to measure. If anyone has any posts/blogs add a link here and I will update the main page with them. A write up on any part would be appreciated.

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Degreaser

Thanks!

Alfrad Axel