EEVblog 1446 - Analog Watt Hour Meters are AMAZING! - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: December 27, 2021, 05:15:14 am
content: Analog Watt Hour energy meters are fascinating! How they work, teardown, and experiments.Thanks to Max Button for sending this in to the mailbag.00:00 - Watt Hour Energy Meters02:11 - Teardown05:13 - What's to stop it taking off?06:40 - Does it work? Testing with a load.07:24 - Can you get free electicity with a neodymium magnet?08:14 - Timelapse of no load creepage08:49 - Anti creep holes10:45 - When this baby hits 88 MPH you're gonna see some serious spin!19:06 - Theory of Operation24:00 - Interesting Design - Jewel bearings25:07 - Interesting Design - Magnetic temperature compensation26:58 - Interesting Design - Full load compensation27:40 - Interesting Design - DimplesThis is how serious they take their metering:https://www.ausgrid.com.au/-/media/Documents/Technical-Documentation/ES/ES12-Metering-Contestability.pdfThis model meter was cancelled from use in 2012:https://www.industry.gov.au/sites/default/files/nmi/certificates-approval/14-2-4.pdf

author: whitesmoke
author_rank: Newbie
timestamp: December 27, 2021, 08:03:53 pm
content: This is the topic I was very interested in, thank you for this great overview!

author: jonovid
author_rank: Super Contributor
timestamp: December 30, 2021, 01:37:41 am
content: piano wire & 1mm drill is what the indoor gardners use to keep costs down.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: January 28, 2022, 07:52:04 pm
content: The pyramid like dimples in the disk @ 28:00 are an artifact of the production process.The sheet metal is made in big rolls, and it's not very flat. The press that stamps the disks out of the sheet metal also presses in the dimples. It first presses the (slightly bent) plate flat, and then presses further to put the dimples in, and this introduces much more local stress into the material then the slight bending force. The end result is that the disk comes out of the press flat, but with dimples.This was fairly common for making steel sheets flatter in all kinds of semi-precise mechanisms. such as the internals of compact cassette players.I do not know what the rectangular shiny sections on the disk are for. My meter at home also has them.I'm guessing, but it may be a calibration correction for the thickness of the disk. I assume the thickness of the disk has an influence on the location or amount of eddy currents in the disk

author: metertech58761
author_rank: Frequent Contributor
timestamp: January 06, 2023, 07:55:37 pm
content: Late to the party... only now noticed this section of the forum.I wasn't aware they had North American-style socket type meters down under. I wouldn't mind getting one for my collection of vintage watthour meters, but seeing that this model had its approval pulled over a decade ago already, it's anyone's guess as to how many are left (presuming that the majority of meters down under get scrapped upon retirement).I believe Doctorandus is correct as to the reason for the stippling on the disk - to help straighten and stiffen the disks (although one modern North American model, the Landis & Gyr MX, was produced with a smooth aluminum disk for a while).As to the shiny spots on the disk, that's pretty unusual. The first thing that comes to mind is it could be a reflective surface for an optical pickup on the fixture used to calibrate the meters. All meters are calibrated under three load conditions - full load (100% test amp rating, 100% power factor), light load (10% test amp rating, 100% power factor), and power factor (100% test amp rating, 50% power factor). I'd assume that the calibration fixture would count how many pulses in a given interval - say 10 pulses for FL and PF, and 1 pulse for LL.