3 ms·
I don't remember the name of the peripheral off the top of my head, but there are some PICs that have a very fast time measurement unit in them. I don't know if
by tonyarkles 9y ago
I don't remember the name of the peripheral off the top of my head, but there are some PICs that have a very fast time measurement unit in them. I don't know if they're fast enough for soil measurement, but there's app notes around for doing TDR-based liquid level sensing with them.
- setq 9y agohttp://www.edn.com/Pdf/ViewPdf?contentItemId=4433411 http://www.edn.com/Pdf/ViewPdf?contentItemId=4433411 Details above. Looks like you can get 3.5ps resolution with an off the shelf PIC after calibration which is pretty impressive!
- tonyarkles 9y agoThat's the one! I was blown away when I first saw it!
- kaybe 9y agoWow! So the price is.. 3$ for the microcontroller, 3$ for the 4 ns comparator, and a few cents for the resistors, capacitors, and 7 GHz transistors (I couldn't find the exact model), and probably some dollars for the rest of the materials such as steel rods and tubes. All in all it looks doable for <50$ easily. That's pretty amazing!