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  1. #1

    How to measure the power clients are 'actually' using???

    I ask this because, beyond installing power bars that monitor usage, I really don't see how it can be done.

    Power clamp readers don't work without pulling the cable out of the plug - obviously that's not going to work, as the youtube video 'How to Use a Clamp Meter: Testing Current on an Appliance' makes clear.

    There is an invention from Taiwan called the AVA-Clampthat offers a technical solution but I can't see it sold anywhere yet

  2. #2
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    What level are you talking about metering at? Rack level? Server level?

    How much of the infrastructure do you control? If it's your own facility then you can meter at the breaker if you want...
    Freethought Internet
    Freethought Internet Limited registered in London No. 5862996. Registered office: The Old Church Hall, 2A Cromwell Street, Lincoln, LN2 5LP. VAT number GB 987 0952 66.

  3. #3
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    CTs in the DBs

    Intelligent Breakers from someone like Mardix

    2BM do an interesting cable clamp, but I've not deployed them in a live scendario.

    Ammeter based PDU's for super simple output readings

  4. #4
    Cheers people. Monitoring the breaker was also my first thought so I will definitely check with our provider now, thanks Ed. Just called 2BM (cheers Steve), they have an intersting monitoring clamp called the iMeter that may do the trick. We would like to be able to go wire by wire, by appliance and power bar. Hopefully will get a full answer tomorrow - will let you know

    By the way, CTs in the DBs ???

  5. #5
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    Quote Originally Posted by Peter_connetu View Post
    Cheers people. Monitoring the breaker was also my first thought so I will definitely check with our provider now, thanks Ed. Just called 2BM (cheers Steve), they have an intersting monitoring clamp called the iMeter that may do the trick. We would like to be able to go wire by wire, by appliance and power bar. Hopefully will get a full answer tomorrow - will let you know
    As we only rent racks, we buy power bars that can not only meter the entire bar, but also on a per-outlet basis. The data centre provider have their own neat little units that sit in line on the 32A commando sockets and also meter on a per-feed basis.

    Quote Originally Posted by Peter_connetu View Post
    By the way, CTs in the DBs ???
    Current Transformer in the Distribution Board.
    Freethought Internet
    Freethought Internet Limited registered in London No. 5862996. Registered office: The Old Church Hall, 2A Cromwell Street, Lincoln, LN2 5LP. VAT number GB 987 0952 66.

  6. #6
    Registered User Array
    Quote Originally Posted by Peter_connetu View Post
    Cheers people. Monitoring the breaker was also my first thought

    By the way, CTs in the DBs ???
    This - as steve suggested the easiest way is to get a LV DB that meters each breaker/customer they are roughly 100-120 more than your standard outlet depending on amperage otherwise just not providing commando sockets and insisting the client uses a metered pdu which *you* supply giving them acses to the web interface means they will be cool too because they can control each socket (turn it on or off), independently verify their usage if they think you are over charging them and depending on the model meter usage by server outlet too.
    Last edited by connected; 4th October 2012 at 07:13 PM.

  7. #7
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    This will be what you want then. They work lovely.

    Minimum useful current measurement we've found to be about half an amp, so they are fine for all but the lightest servers. We find you need to turn it around the cable or turn the cable a bit, as the reading can vary a little, but only perhaps 10 - 20 degrees. There just seems to be a high spot somewhere, but when confirmed against a passthru calibarated meter, it is all but close enough.

    Megger MMC850 Multicore Clamp Meter - MMC850 AC Current Clampmeter

    Shop a bit, you can have then for just over 100.

    Works fine on inbound PDU cables and back of servers. Won't work if you have over-braided Hi-tuff and similar from C-form to PDU though. Also works on twin & Earth cable too. You just dial the cable into it.
    Peter Knapp - CCS Leeds Ltd - www.ccsleeds.co.uk
    Coal Road, Leeds. LS14 2AQ / Co. reg: 03507910 / VAT reg: GB 698 2027 05 / Tel: 0113 294 66 99
    UK Leased Lines | Hosted VoIP & SIP Trunks | EFM - Ethernet First Mile
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  8. #8
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    I'm intrigued to hear more about the clamp jobbies as I thought the general consensus was that they were very inaccurate?
    Jon Roberts, M.D of RackSRV Communications Ltd
    UK specialists in Dedicated Servers, Colocation & Rackspace
    Company: 06856870 VAT: GB 934 7073 15 Tel: 0330 229 1000

  9. #9
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    Quote Originally Posted by Jon-RackSRV View Post
    I'm intrigued to hear more about the clamp jobbies as I thought the general consensus was that they were very inaccurate?
    My experience with clamp meters is that they're mostly a pile of pony.... inaccurate and not to be trusted for anything other than the most rudimentary ball park readings.

  10. #10
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    Quote Originally Posted by markcastle View Post
    My experience with clamp meters is that they're mostly a pile of pony.... inaccurate and not to be trusted for anything other than the most rudimentary ball park readings.
    Anything up to 150% inaccurate.

    Inline meters at the commando for rack monitoring, raritan and apc for outlet monitoring, metered pdus for podule monitoring, snmp able ups and power correction kit, big LCD on the mains - we check them all :-)

  11. #11
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    AFAIK the "inline meters" are also clamp technology as well though? The only difference is they're clamping a single wire instead of multi-core (so if you "manually" clamp a single wire it's equally as in/accurate)? Or is that not so?

  12. #12
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    If you clamp only the live you generally get a much more accurate reading.

  13. #13
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    Quote Originally Posted by Layershift Damien View Post
    AFAIK the "inline meters" are also clamp technology as well though? The only difference is they're clamping a single wire instead of multi-core (so if you "manually" clamp a single wire it's equally as in/accurate)? Or is that not so?
    As Steve said. Single core CT's can be down to sub 1% accuracy if you pay enough..
    Peter Knapp - CCS Leeds Ltd - www.ccsleeds.co.uk
    Coal Road, Leeds. LS14 2AQ / Co. reg: 03507910 / VAT reg: GB 698 2027 05 / Tel: 0113 294 66 99
    UK Leased Lines | Hosted VoIP & SIP Trunks | EFM - Ethernet First Mile
    Free Install and Cisco Router on Fully Managed EFM at up to 20Mb/s only 300 per month

  14. #14
    2BM have just come back offering me an audit kit for 1499.00.. They said that legally they need to say that the kits give a 0.5Amp inaccuracy reading, but they are convinced that's it's more like 0.1Amp. The Megger clamps are advertising 0.1 on their website, but not sure what '...a resolution to 0.1' actually means. Does that mean it's possible, or that it always gets to that accuracy? My guess is the former, as Pete-CCS points out (cheers for that).
    Last edited by Peter_connetu; 5th October 2012 at 12:15 PM.

  15. #15
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    Not the best pic, and to be fair, the clamp meter was flickering between 0.5 and 0.6 - I just caught it at the right time, but that is the cable through the plug in looped via the clamp.

    Fairly accurate - certainly enough so for a quick check..

    IMG-20121005-00086.jpg
    Peter Knapp - CCS Leeds Ltd - www.ccsleeds.co.uk
    Coal Road, Leeds. LS14 2AQ / Co. reg: 03507910 / VAT reg: GB 698 2027 05 / Tel: 0113 294 66 99
    UK Leased Lines | Hosted VoIP & SIP Trunks | EFM - Ethernet First Mile
    Free Install and Cisco Router on Fully Managed EFM at up to 20Mb/s only 300 per month

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