How to measure 121 Giga Watts with a 121GW meter ? - Page 1
Forum section: electronics / general

author: ez24
author_rank: Super Contributor
timestamp: July 31, 2017, 01:19:43 am
content: HiEver since I read that the 121GW meter is based on a 121 Giga Watt statement in a movie, I have wondered how someone could measure 121 Giga Watts. My guess is measure the voltage drop across a shunt. With 121 GW my guess a shunt the size of an aircraft carrier would be needed.So how can you measure 121 GW with a 121GW? I assume you cannot just use the leads that come with the meter.As a rough estimate, the US generates about 4,000 terawatt-hours (TWh) a yearTerabyte = 1,024 GigabytesSo the US uses less than 121 GW a year.I think the first thing is limit the voltage to the voltage limit of the meter, so no million volts.. So I wonder if a 10 foot diameter bus bar would work?Any math wizards?

author: WastelandTek
author_rank: Frequent Contributor
timestamp: July 31, 2017, 01:33:35 am
content: meh, its nothing compared to the Disaster Area show I was just at

author: rs20
author_rank: Super Contributor
timestamp: July 31, 2017, 01:43:20 am
content: You do not measure power with 2 leads, you need 3 or 4 leads. This is because power = voltage * current, you need to measure voltage and current independently.A (large?) nuclear reactor generates approximately 1.21 GW.Assuming DC power, and a max voltage of 600 VDC, we'd be dealing with 200 MA (megaamps). Now clearly the meter cannot handle 200MA, but let's assume the shunt in the meter is 10 milliohms. If we put a a 0.1 nanoohm resistor in parallel with that shunt, we'd have 2A running through the meter when the 0.1 nanoohm shunt is dealing with 200MA; and it's scale accordingly. The display on the meter would simply be "off" by a factor of 100,000,000, simply place a sticker over the 10A switch labelled "1GA" and read the meter accordingly, and you're good to go.The 0.1 nanoohm shunt will dissipate 4 MW. Good quality cooling would be encouraged.If you ever encounter 1.21GW, it's much more likely to be 121 kV * 10 kA. This would actually be "quite straightforward" to measure, provided you could arrange a similar voltage divider as well as a current "splitter/divider". The shunt, 2 microohm, would dissipate much less heat: a completely manageable 200 W.You'd need to measure voltage and current separately, the 121GW probably doesn't have a power measurement mode where it multiplies the two for you. A metrahitt-whatever-it's-called could do that job, though, with suitable stickers redefining what the voltage, current and power ranges mean.

author: Brumby
author_rank: Unknown
timestamp: July 31, 2017, 02:09:39 am
content: Quote from: ez24 on July 31, 2017, 01:19:43 amAh ... Correction. It is only in computer circles that the Giga/Tera factor is 1024 - just because they like their powers of 2.**Engineers do it right ... it's 1,000.** Actually, even in computer circles that is not consistent. Sometimes you will find - especially in the marketing department - someone will use a factor of 1,000 so they can describe (typically hard drives) as having a 1 TB capacity when it holds less than 1024*1024*1024*1024 bytes. It gets even more bizarre when they use a mix of 1,000 and 1024.

author: Tom45
author_rank: Frequent Contributor
timestamp: July 31, 2017, 03:30:32 am
content: If someone gave me the task of measuring 121GW, I'd tell them once they get 121GW through a single transmission line get back to me and I'll then start thinking about how to measure it. I wouldn't expect to hear from them again.

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: July 31, 2017, 06:56:32 am
content: I'm reasonably sure that the Smiths car dashboard instruments go up to 55GW, so they probably make higher ranges too.http://gridwatch.templar.co.uk/Most likely the current -which is the problematic quantity- would be measured with a current transformer. Straight bar primary, multiturn secondary. Or, a hall effect device could measure the magnetic field near the conductor. Not so accurate, but works for DC.Voltage, just f'ing great potential divider resistor, likely the type with rain shielding discs on it.Though, 121GW is more than double the UK peak demand.

author: boffin
author_rank: Unknown
timestamp: July 31, 2017, 07:12:26 am
content: Quote from: ez24 on July 31, 2017, 01:19:43 amActually the 2^10 (1024) multipliers are:Tebi(byte),Gibi(byte),Mebi(byte),Kibi(byte)per the IEC.https://en.wikipedia.org/wiki/Kibibyte

author: Ampera
author_rank: Super Contributor
timestamp: July 31, 2017, 09:42:35 am
content: Quote from: boffin on July 31, 2017, 07:12:26 amThis is correct. The SI multipliers are 1000s of the previous one i.e.1 Kilobyte = 1000 bytes1000 Megabyte = 1000 KilobytesetcThis also repeats for bits which is a more (pure?) measurement of data.1 byte = 8 bits1 Kilobit = 1000 bits1 Megabit = 1000 Kilobitsetc.The IEC has set down a standard (which basically turned into a situation of good luck with that) that are supposed to signify the powers of 2 deal. At this point it's largely arbitrary, but you have to be careful, as many people (Like the OP) have their own standards, which are technically wrong, but understandably so because so many people have said so many different things, it's confusing to no end.As boffin said, the first two letters of the standard SI multipliers are used, followed by bi (Kibi, Mebi, Gibi, Tebi, Pebi etc.) the same will then follow for byte vs bit mesaures1 byte = 8 bits1 Kibibyte = 1024 bytes & 1 Kibibit = 1024 bits1 Mebibyte = 1024 Kibibytes & 1 Mebibit = 1024 KibibitsThe distinction is for the most part unnecessary unless you are dealing with lower level stuff that would make the IEC standard your best friend. For your average flash stick or hard drive however, it's not that big of a difference, even if it is confusing, for most people.

author: ebastler
author_rank: Super Contributor
timestamp: July 31, 2017, 11:40:54 am
content: Quote from: ez24 on July 31, 2017, 01:19:43 amYou have your units mixed up there, confusing power and energy.The total "consumption" of electrical energy in the U.S. is 4,000 TWh per year. You have to divide that by the number of hours per year to get the average power:(4,000 TWh/a) / (24*365 h/a) = 0.456 TW = 456 GW.So the United States provide a convenient DUT to test an even stronger meter than the 121GW.

author: Avacee
author_rank: Unknown
timestamp: July 31, 2017, 11:55:48 am
content: The actual value in the film is 1.21 GW ... your task just got 100 times easier

author: Zero999
author_rank: Super Contributor
timestamp: July 31, 2017, 02:48:26 pm
content: Quote from: rs20 on July 31, 2017, 01:43:20 amExcept shunts wouldn't be used to measure such high currents. A hall effect sensor is normally the method of choice for measuring such high currents because there's hardly any power loss.

author: G0MJW
author_rank: Regular Contributor
timestamp: July 31, 2017, 03:10:20 pm
content: Quote from: ez24 on July 31, 2017, 01:19:43 amI thought it was 1.21 GW.Its not an unachievable amount of power, my local power station generates 1.36GW but that's OK as its not likely to be travelling at 88mph unless something has gone seriously wrong in the turbine hall. The associated 750kV transmission lines are typically carrying several GW of power.As far as measuring GW power transfers, "from a distance" comes to mind. Either that or get someone else to do ithttp://www.gridwatch.templar.co.uk/. You don't need a shunt to measure current in a transmission line, you can measure the magnetic field and electric field. This is much easier if it is AC because you only need to measure the varying component.Mike

author: German_EE
author_rank: Super Contributor
timestamp: July 31, 2017, 04:21:48 pm
content: Measure the voltage at the power station end of the transmission lineMeasure the voltage at the load end of the transmission lineWatts = Voltage Drop ^2 / Line Resistance

author: Yansi
author_rank: Super Contributor
timestamp: July 31, 2017, 04:46:43 pm
content: Quote from: boffin on July 31, 2017, 07:12:26 amFuck the the IEC with this. Hate this shit hard. Used kB as 1024B, MB as 1024kB ever since and will continue doing so. Not interested in the KiD, sorry, KiB stuff.

author: skarecrow
author_rank: Regular Contributor
timestamp: July 31, 2017, 05:09:08 pm
content: Quote from: Avacee on July 31, 2017, 11:55:48 amActually in the movie it was jigga-watt. :-PSent from my XT1565 using Tapatalk

author: rstofer
author_rank: Super Contributor
timestamp: July 31, 2017, 05:11:29 pm
content: Measuring the 1.21 GW power as 121 kV at 10,000 Amps is trivial. We simply use a 10,000:5 current transformer and a 150 kV:120V voltage transformer.http://new.abb.com/high-voltage/instrument-transformersTherefore, split the 121 GW into 100 parallel paths, measure the voltage once and measure the current 100 times.Maxwell would be proud of the fields surrounding the measuring station.

author: skarecrow
author_rank: Regular Contributor
timestamp: July 31, 2017, 05:22:23 pm
content: Quote from: Yansi on July 31, 2017, 04:46:43 pmDamn right! 1k has been 1024 since I started writing my own games in Commodore BASIC on my C64 when I was 4 years old. 1k will always be 1024 in my book, I don't care what your book says. Y2K is still over 30 years in the future!!! I can just about guarantee the year 2048 brings about a LOT more computer problems than the year 2000 did.Another thing I noticed in the OP (sorry I can't easily do 2 quotes on my phone) is a little math error. Here is the quote...As a rough estimate, the US generates about 4,000 terawatt-hours (TWh) a yearTerabyte = 1,024 GigabytesSo the US uses less than 121 GW a year.Someone else already mentioned getting the units mixed up. I think 4000*1024 is a little more than 121. 4000TW==4,096,000GW. So obviously the US uses more than 121(1.21)GW/GWh/whatever. I think the OP read it backwards or something.Sent from my XT1565 using Tapatalk

author: Zero999
author_rank: Super Contributor
timestamp: July 31, 2017, 05:39:47 pm
content: Quote from: skarecrow on July 31, 2017, 05:22:23 pmI can understand measuring RAM in KiB and MiB, as it is arranged in powers of 2, so it makes sense and numbers easier to write. However, I think it's confusing for other things such as current and power, which don't normally occur in powers of 2.I think you'll be fine here if you refer to memory as 1KB = 1024B but you'll get flamed if you start using it for Ohms.

author: skarecrow
author_rank: Regular Contributor
timestamp: July 31, 2017, 06:17:35 pm
content: Quote from: Hero999 on July 31, 2017, 05:39:47 pmA general rule of thumb I go by, if it's computer related it's 1024, otherwise it's probably 1000. When it comes to y2k that is a computer related event, therefore 2048 is the correct year. That 1GB hard drive is supposed to have 1,073,741,824 bytes.Not computer related, 1K ohm is 1000 and $50k is $50,000.Sent from my XT1565 using Tapatalk

author: ebastler
author_rank: Super Contributor
timestamp: July 31, 2017, 07:20:46 pm
content: Quote from: skarecrow on July 31, 2017, 06:17:35 pm