Jim

Nice job by Edward. Thanks for the link!

I was aware that there was magnetic coupling in the meter; sensing that was in fact the first thing I tried. Unfortunately, there’s about 3 amps of AC going thru my water meter (!?), and the 60 cycle magnetic field from that so thoroughly drowns out what I could pick up from the moving magnet in the meter that I gave up. I made some serious attempts to null it out, but failed. Filtering wouldn’t work either because at high flow the fluctuations from the magnet could be around 60 Hz. (There was a little comment about it in this post.)

It was an interesting moment when I first put an Amprobe around that pipe! Of course I tried to figure out why that current was there, but failed at that, too. I did get far enough to be fairly convinced it wasn’t a wiring problem in my house – but rather a problem in a neighboring house sharing the same power transformer. I suppose I should revisit that some day.

Of course maybe the 5 or 6 bytes of 0xE I’ve attributed to being sync bytes are really the serial number, and my meter happens to have an unusual serial number that happens to encode to 5 or 6 bytes of 0xE. Seems kind of unlikely, but without more information (protocol details or observations from other meters) it’s hard to know.

If there is such a serial number poll command/mechanism, it’s quite plausible that when the R900 first starts up – maybe after getting a new battery? – it polls the meter encoder for a serial number and then just remembers it. No need to ask again. But I guess I’m not quite bold (or curious) enough to open the R900 and pull the battery (or look for a reset switch) while logging the data from the encoder.

Also plausible would be that the commercial account mapping is between the account and the R900. That device has a 10-digit serial number, and could very easily include it in every transmission. And I saw reference in some Neptune doc to a 10-digit number in every transmission from an MIU (Meter Interface Unit). Maybe the same number?

My water bill shows an 8 digit number as “meter number” which matches a number in the cast bronze housing of the meter. I doubt that there’s any way for the “encoder” part to be able to know that number (unless it was hard coded in by switches/jumpers/links when the encoder was installed on the meter housing).

I ran across mention of the 1203 protocol in my research, too. While I thought finding the details of that protocol might help a lot – and I tried to find it (but failed) – I seem to recall only reading that is was very similar, but not necessarily identical to the Neptune protocol. If anybody reading this happens to have a copy of that protocol, I’d love to see it!

Jim

I’m happy to share my experiments, but the real credit for in depth experiment and reporting goes to Adam Seychell.

Sounds like your setup is well on the way to making some good etchant. I’m a little surprised by how large the temperature rise is, but that probably means it will just finish more quickly. Your multi-level failsafe setup sounds quite sensible. If there are any rustable metal objects nearby/downwind, I’m sure they’ll fare much better with your carpet covering to catch any remaining aerosol.

I’ll be interested to hear how you make out with 200ml of etchant. My usual tank (the spaghetti box container) holds about a liter. If I do 2 small boards – maybe 2″ x 3″ – the second one takes noticeably longer to etch than the first from the etchant being temporarily partially exhausted. (And I lay out my boards with resist on unused areas just so the etchant won’t have to work so hard!)

I’m looking at making another tank (for our local hackerspace) but with the dimensions I was picturing (maybe 2x10x20cm) it’s well under a liter, and I’m concerned about the performance with so little etchant.

Thanks for your comments!

Jim

First: I am VERY happy nothing serious happend to you in your experiment with the high-percentage-H2O2 and the boiling acid. That video looks scary as hell!
8-0
I used the starter etchant (HCl + H2O2) since long time, but i just set up a batch of your slower formula. It should yield 2x 2dl (I make it in 2 batches. Too scared by the full ammount of fuming HCl in one place to be honest).
It turned brownish in minutes and is bubbling with the bubbler since 30mins.
The bottle is quite warm to the touch. Around 30°C i would say (Feeling. Not measured) and it is around 2-3°C outside…
Will check in the morning again.

And yes: It is placed outside, in a glassbottle (The airstone was just the diameter of the bottlethroat) and the splashguard is installed (A long, inverted cone willed with absorptive papertowel) . The bottle is in a big glass-jar (in case the bottle blreaks due to thermal stress) and all this sits in a plastic-crate (last line of defense). I also covered the crate with a small carpet (IKEA) intended to use in the bathroom… Serves as minimal drop-on-protection…

Thanks for the real in deep analysis in all your 9 posts about this experiment-series. I read them all and i think what i do now is more a longtime-experiment than the covering of a real need since i already had the etchant (starter) at hand. And since i always etched only 1-2 very small boards every month or months, i think that would have served me equally well. But the learning and information about the really interesting chemistry here is what drove me to the point where i wanted to try it out.
Thanks!