Pulse output from a water meter (mechanical question) - Page 1
Forum section: electronics / projects

author: e100
author_rank: Frequent Contributor
timestamp: February 12, 2018, 05:38:13 am
content: Is anyone familiar with this type of water meter that has a reed switch mounted above a dial with a magnet perched on top?With the reed switched removed(The image gives the optical illusion of a hole through the plastic cover, but it's actually solid on top.)Are these types of meters easily configured to read a different dial?Do the red pointers simply pull off, and can I simply rotate the transparent cover so that the reed switch is over a different dial?

author: capt bullshot
author_rank: Super Contributor
timestamp: February 12, 2018, 06:20:18 am
content: Don't know about your original quiestion.What I did with one of these meters: pointing a laser at the fast rotating (black) wheel and detecting the intensity changes to have a real high resolution counter.

author: e100
author_rank: Frequent Contributor
timestamp: February 12, 2018, 06:44:30 am
content: Quote from: capt bullshot on February 12, 2018, 06:20:18 amInteresting, specs for cheap 1mw lasers quote a lifespan of about 5000 hours or thereabouts, which is only 200 days if operated continuously. Do you get a longer life if you run at a fraction of full power or in pulsed mode?

author: capt bullshot
author_rank: Super Contributor
timestamp: February 12, 2018, 06:59:35 am
content: Yes, the lasers lifespan was a concern - but turned out to be longer than expected. I've used a modded simple laser pointer (remove the battey and pushbutton). The laser output power regulation circuit was so primitive, I could modulate the output just by applying a 170kHz square wave as the power supply (instead the battery). The modulation was used to frequency selective receive the reflected light (ambient light suppression).This thing worked for 4 to 5 years, then the water meter was replaced and I switched to inductive pickup - as the meter provided for that. I never saw the (el cheapo) laser degrade ...

author: e100
author_rank: Frequent Contributor
timestamp: February 13, 2018, 04:03:49 pm
content: Replying to myself, relocating the sensor is possible.The hardest part was making a tool to unscrew the metal retaining ring that holds the whole thing together.

author: fourtytwo42
author_rank: Super Contributor
timestamp: February 13, 2018, 08:21:38 pm
content: Quote from: e100 on February 12, 2018, 05:38:13 amIn the uk I have a similar meter but fitted my own reed switch to it, the lowest order dial has a tiny magnet embedded in it, you can see it in your picture as a silver disk that operates the reed switch. My meter belongs to the water company so I could not possibly disasemble it to swap the pointers and i have to ask why you would want to do that ?In my case the lowest dial does a revelution every Litre (horrid euro measure) and my software in the house just accumalates those the same as the meter does and displays the same total to a reselution of 1 Litre. Following your sugestion and moving the magnet dial to say 100's would mean my reading reselution would drop to 100 Litres and I cannot figure why I would want to do that

author: jack-daniels
author_rank: Contributor
timestamp: February 13, 2018, 09:02:22 pm
content: Quote from: fourtytwo42 on February 13, 2018, 08:21:38 pmI think the dial the sensor is on is tenths of a gallon and the dial to the left is hundredths of a gallon.So if he swapped to this one he'd get greater usage accuracy?EDITLooking at it again, I guess the sensor only picks up one full revolution at a time so the dial it's on equates to 1 pulse per gallon where as the one to the left will equal one tenth of a gallon per pulse (or 0.378541 Litre).

author: fourtytwo42
author_rank: Super Contributor
timestamp: February 13, 2018, 09:27:32 pm
content: Quote from: jack-daniels on February 13, 2018, 09:02:22 pmAhhhhnow I understand what I missed in the question thank you