Interesting measuring device on eBay

solar_dave
solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
in General Solar Power Topics #1
http://www.ebay.com/itm/EVSE-EV-Car-Charger-Electric-Meter-Vehicle-Charging-Station-Network-j1772-UL-25-/181024483131
This is the newest addition to our meter product line, our Universal OmniMeter II v.3 UL accurately meters all electrical systems commonly used in the world--120V, 2-wire, single-phase through 240V, 3-phase 4-wire, 50Hz or 60Hz. Meter up to 5000A!

...

SMARTER than ever!! Reads kWh, Reverse kWh (for solar), Voltage on each line, Current on each line, Power (watts) on each line, Power Factor on each line, Maximum Demand, CT Ratio, 6 months of monthly reads stored on-board the meter with 4 TOU rates, 4 Times of day, 4 Seasons, Weekends and Holidays!! All readable and log-able via RS-485 and user friendly PC, Mac and Linux software.
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  • mtdoc
    mtdoc Solar Expert Posts: 600 ✭✭
    #2
    Re: Interesting measuring device on eBay

    Great find! The company, EKM metering, has their own website with more info, direct sales, and a user forum. The prices for their meters is good,even with the additional cost of the CTs. Their monitoring software looks nice as well.

    The sell THIS single external CT meter. This would be a nice way to measure loads that are not amenable to Kill -A Watt measurements. Only $58.

    I'm wondering if this would work for DC line measurements as well? There's a few DC wires in my ePanel I'd love to put a CT on and be able to monitor and plot current remotely.

    Thanks Dave!
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #3
    Re: Interesting measuring device on eBay
    mtdoc wrote: »
    I'm wondering if this would work for DC line measurements as well? There's a few DC wires in my ePanel I'd love to put a CT on and be able to monitor and plot current remotely.

    Thanks Dave!

    Basic problem: Current transformers (unless built with superconductors) do not work with DC.

    Clamp-on DC ammeters use a Hall-Effect current sensor rather than the simple CT used by AC-Only ammeters.

    That said, if you could overcome the stability problems, you could theoretically use a non-contact Hall-effect sensor to do a similar thing for DC. But the meter would require an analog voltage detector input that is stable for small DC voltages. I think it ends up being easier/cheaper to use a shunt in most cases.
    SMA SB 3000, old BP panels.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4
    Re: Interesting measuring device on eBay

    Current Transformer type transducers only work with AC--DC, they will show no current flow with DC current.

    Regarding the single point CT meter--It may not be able to display +/- power flow.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • mtdoc
    mtdoc Solar Expert Posts: 600 ✭✭
    #5
    Re: Interesting measuring device on eBay

    Doh! Ok, thanks guys. No CTs on DC. :blush:

    Thinking about it, even with my meager physics, electronics knowledge, that makes perfect sense. Ya need that sine wave..
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #6
    Re: Interesting measuring device on eBay

    Interesting find, Dave, Thanks!

    I do have a need for a 3-Phase 4W service at my in-town workshop. The "Utility" -- PG&E -- has such unreliable power that really need an on-line back-up system. We have had 13 outages of varying durations in the past year. Upon calling them for the duration and cause for these outages in the prior 12 months, they responded several months later with, "What Outages?"!

    There IS a StupidMeter at the site, but since they are unregulated, now they could care less.

    I really need a power-line Volage monitor with fine resolution. I do not care about Kwh for this application, would like to be able to watch voltage excursions, measure duration and see just how the power went OFF and back ON.

    They have solved my problem of unpredictable power service. The power was cut off on 10/19/12, (after they had to replace the transformers feeding our block, and is still off. They felt that because there were "temporary connectors" at my service weatherhead, there was unpermitted work that occurred onsite. They do not keep records of ititial connection and parameters of that, so, I had to try to PROVE that I had a electrical Permit for a panel upgrade back in 1990 ... and so on.

    May have power in the next week or so. I wonder if PG&E is a division of "S" Electric??

    They have accomplished one thing. I am very grateful to have any Grid power, when available. I'll probably shut up about reliability for a while. My report from the fourth world - CA -. Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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  • chevenstein
    chevenstein Solar Expert Posts: 100 ✭✭
    #7
    Re: Interesting measuring device on eBay

    That's a pretty good price for that kind of meter, but it's not an unusual product or or especially great price: that kind of device from other vendors is used for all sorts of commercial and industrial applications and can be had in the $400 - $500 range when you're a dealer (which you would be even if you're a very small engineering services firm). I used to install a product from Electro-Industries/Gaugetech (http://www.electroind.com) in distributed generation plants that I instrumented, but that was a long time ago and EIG doesn't make that particular meter any more (though their Shark line looks like the modern equivalent, I do not have pricing for it though (but again, if you become a dealer you will be able to get them for 15-40% off of list)).

    For those looking for this kind of meter with CTs for their home/hobby projects I would recommend saving searches on eBay, as I've seen new, unused multi-thousand dollar pieces of equipment go for a hundred bucks when it becomes obsolete and someone who had stocked it can't sell it anymore so they simply want it gone (or gave it to an employee who decided he didn't want it so it ended up on eBay). Either way, if you look you will find deals but you have to know what to look for.

    Note that most of these devices will have a Modbus interface over long range serial (RS 422/485), which will require about a $20 converter to get into your PC. Once on the PC there is all sorts of software that can talk modbus, if you like coding I would recommend the pymodbus library for python: http://code.google.com/p/pymodbus/
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  • chevenstein
    chevenstein Solar Expert Posts: 100 ✭✭
    #8
    Re: Interesting measuring device on eBay

    PS - I don't mean that that price isn't much less than 500 bucks (it is), I mean that for a few hundred more than the OP's post you can get an industrial quality meter that's probably qualified for utility metering applications, depending on the model.
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