作者: so? 時間: 2009-9-9 17:40 標題: 萬用表度電器,請問2支針要放在電器那個位置?
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作者: so? 時間: 2009-9-9 18:48
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作者: BurnDuck 時間: 2009-9-9 18:58
原帖由 so? 於 2009-9-9 06:48 PM 發表
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我好中意呢個回覆作者: kwan3k 時間: 2009-9-9 20:09
紅 +
黑 -
作者: cli 時間: 2009-9-9 22:59
實際好簡單，2支針放在要度的電器有電的位置就可以！
作者: den 時間: 2009-9-9 23:06
你度volt 都可以 但度 amp和 w 你隻表可以度幾多 amp先 呢類型度好細amp炸喎(正常黎講) w就應該唔得
*ching 小心電死你呀* 如果你用來度ac =..=
作者: Motti_sir 時間: 2009-9-10 01:04
度amp 亂咁short野玩魔術
作者: shingzhk 時間: 2009-9-10 02:07
原帖由 so? 於 2009-9-9 18:48 發表
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我跟
To:樓主
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作者: FireBlack 時間: 2009-9-10 02:18
If you are talking about AC measurement, you cannot measure Watt with this meter. There is no such feature. You need to buy a Watt meter.
作者: low238 時間: 2009-9-10 03:04
原帖由 so? 於 2009-9-9 18:48 發表
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真係同個名好岩FEEL
兩支野放落要度個野度一頭一尾
作者: shingzhk 時間: 2009-9-10 10:44
原帖由 low238 於 2009-9-10 03:04 發表
真係同個名好岩FEEL
兩支野放落要度個野度一頭一尾
唔係咖,樓主話想度[電器],電壓就唔度都知220V peak
要度Current就祝佢好運啦
w就....
,要度r都可以理解,但要度呢3樣我就真係
[???????????????????????//]
[ 本帖最後由 shingzhk 於 2009-9-10 11:24 編輯 ]
作者: Leopard 時間: 2009-9-10 10:59
認真
樓主知唔知 V=IR 同P=VI 係乜
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作者: stephenwong 時間: 2009-9-10 11:17 標題: 回覆 11# 的帖子
AC 220V from your socket is NOT 220V peak-to-peak ah!
220V is an rms value, which equals to 220 x 1.414 = 325V peak and 650V peak-to-peak.
That's my understanding.
Stephen Wong @ Hong Kong
作者: shingzhk 時間: 2009-9-10 11:23
原帖由 stephenwong 於 2009-9-10 11:17 發表
AC 220V from your socket is NOT 220V peak-to-peak ah!
220V is an rms value, which equals to 220 x 1.414 = 325V peak and 650V peak-to-peak.
That's my understanding.
Stephen Wong @ Hong Kong
OK,係我搞錯
原本想打Peak Value 220V ,P2P係440V (點知原來係rms)
作者: so? 時間: 2009-9-10 12:40
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作者: shingzhk 時間: 2009-9-10 13:03
原帖由 so? 於 2009-9-10 12:40 發表
我買來量電器既電功率w
我見萬用表$20有交易
功率表就要$100
我承認貪平
完
唔係話緊你貪唔貪平
根本係2個作用,萬用錶常用黎度DC電路既Resister, Voltage, current(低),好少少既有得度埋cap
基本上係for circuit checking / debug ,一般人買左都冇乜用
功率計既話,鴨記最平果隻(好似得一隻),都要$230左右
作者: so? 時間: 2009-9-10 13:06
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作者: Leopard 時間: 2009-9-10 14:04 標題: 回覆 17# 的帖子
其實你唔驚死的話可以用錶串聯拖板的live入你件電器度A
然後再用個A數乘電壓
前題係確定你件電器唔過2200W, 然後就係你相信個錶真係MAX頂到AC10A
呢D咁高手的行為, 我就唔敢做嘞
作者: stephenwong 時間: 2009-9-10 15:07 標題: 回覆 18# 的帖子
Use a clam meter, or a wattage meter.
Stephen Wong @ Hong Kong
作者: Leopard 時間: 2009-9-10 18:42 標題: 回覆 19# 的帖子
唔洗回我, 我只係因應佢問DMM來答, 亦講明危險
and clam is 蝌蚪
clampmeter 才是鉗錶
作者: lorym 時間: 2009-9-12 12:01
原帖由 Leopard 於 2009-9-10 02:04 PM 發表
其實你唔驚死的話可以用錶串聯拖板的live入你件電器度A
然後再用個A數乘電壓
前題係確定你件電器唔過2200W, 然後就係你相信個錶真係MAX頂到AC10A
呢D咁高手的行為, 我就唔敢做嘞
咁都唔一定係 WATT 架喎！
作者: Motti_sir 時間: 2009-9-12 16:36
新手學野:
唔係watt 會係d 咩??
同埋如果想度watt, 又應該點做??
作者: jwong852 時間: 2009-9-12 16:46
原帖由 Motti_sir 於 2009-9-12 16:36 發表
新手學野:
唔係watt 會係d 咩??
同埋如果想度watt, 又應該點做??
Power (unit is Watt) in AC circuit = Voltage(in RMS value) x Current(in RMS value) x Power Factor.
OR
Power = Average value over a period of the integration of instaneous voltage x current.
These were taught in Electronic/Electrical Engineering year 1.
If you only have Form 5 physics level, read books of Elementory Electrical Engineering or Google "Power Factor".
[ 本帖最後由 jwong852 於 2009-9-12 19:24 編輯 ]
作者: Motti_sir 時間: 2009-9-12 19:22
又係喎~ 唔記得左有power factor
不過又想知, watt meter 點樣考慮埋power factor 得出正確數字?
我夾o係中間
form7 phy + o岩o岩入HDelectronic year1
作者: jwong852 時間: 2009-9-12 19:36
原帖由 Motti_sir 於 2009-9-12 19:22 發表
又係喎~ 唔記得左有power factor
不過又想知, watt meter 點樣考慮埋power factor 得出正確數字?
我夾o係中間
form7 phy + o岩o岩入HDelectronic year1
Analog Wattmeter 係 用voltage 推針錶一個coil (stator or rotor), current 推另一個coil. Result 就係 instantenous V x I. 針錶有隋性, 會顯示average value = true power.
Digital wattmeter 係用高速sampling, A/D. instantaneous V value X I value. (V X I 可以係正或負數) mathermatical average 就係 true power.
Vrms 同 Irms 用同樣方法, take instantaneous V value (或 I value), take square, take average, 最後要 take square root 得出 Vrms 或 Irms.
Power Factor 就要用以上result 計出黎:
P.F. = True Power / (Vrms X Irms).
我設計果個wattmeter就係咁計 :
http://www.hkepc.com/forum/viewthread.php?tid=1207998&extra=page%3D2
[ 本帖最後由 jwong852 於 2009-9-12 19:38 編輯 ]
作者: gulakpi 時間: 2009-9-12 19:50
Electricity is not dangerous if you know what you are doing!
The way you asked, it seemed you do not even have any knowledge of elementary physics. Be careful, don't kill yourself!
作者: Motti_sir 時間: 2009-9-12 23:40
超sad~ 學校無學過true power = Prms x P.F.
最多只係計Prms 同埋P.F.
最後想問多少少野.....
true power =/= Vrms x Irms
係咪因為V同I 唔同phase?
作者: setom 時間: 2009-9-12 23:48
其實樓主你需要係呢類product..
http://www.hkepc.com/forum/viewthread.php?tid=1314706
等有機會再團購啦!
http://www.hkepc.com/forum/viewthread.php?tid=1317167
作者: so? 時間: 2009-9-13 02:37
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作者: jackli 時間: 2009-9-13 09:35
間唔中都會有唔少人出post...
唔理power factor
作者: jwong852 時間: 2009-9-13 11:09
原帖由 Motti_sir 於 2009-9-12 23:40 發表
超sad~ 學校無學過true power = Prms x P.F.
最多只係計Prms 同埋P.F.
最後想問多少少野.....
true power =/= Vrms x Irms
係咪因為V同I 唔同phase?
係咪因為V同I 唔同phase? ------------- 係
就算同phase, 唔同波型, power factor 都唔係=1.
Power 只有continuous power, peak power, 無 rms power !
[ 本帖最後由 jwong852 於 2009-9-13 11:11 編輯 ]
作者: Offer 時間: 2009-9-13 11:30
原帖由 jackli 於 2009-9-13 09:35 發表
間唔中都會有唔少人出post...
唔理power factor
因為佢地多數在50V DC以下玩,AC計算Power不是那麼簡單
作者: Motti_sir 時間: 2009-9-13 13:42
原帖由 jwong852 於 2009-9-13 11:09 發表
係咪因為V同I 唔同phase? ------------- 係
就算同phase, 唔同波型, power factor 都唔係=1.
Power 只有continuous power, peak power, 無 rms power !
有道理!!
rms power 係無意思~
要求教科書講多少少
唔該晒各位ching
又學到野
作者: ciel 時間: 2009-9-13 16:31
原帖由 stephenwong 於 2009-9-10 11:17 發表
AC 220V from your socket is NOT 220V peak-to-peak ah!
220V is an rms value, which equals to 220 x 1.414 = 325V peak and 650V peak-to-peak.
That's my understanding.
Stephen Wong @ Hong Kong
Typo, I guess.
220 V x 1.414 = 311 V
230 V x 1.414 = 325 V
From Wiki:
In Europe, agreement was reached to change the various national voltages, which ranged at the time from 220 V to 240 V, to a common European standard of 230 V.
So in UK (originally 240 V), as an interim measure, electricity suppliers can work with an asymmetric voltage tolerance of 230 V+10%-6% (216.2-253 V).
France, Germany, Greece, Hungary, Ireland, Italy, Netherland etc. all changed from 220 V to a nominal 230 V value.
Will Hong Kong change also to 230 V?
There was precedent that Hong Kong had changed the AC voltage value. In fact many years ago the Hong Kong AC voltage was 200 V.
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原帖由 jwong852 於 2009-9-13 11:09 發表
Power 只有continuous power, peak power, 無 rms power !
It is interesting. The term 'rms power' seems originating from the HI FI industry.
Why there is no such thing as 'RMS watts' or 'watts RMS' and never has been
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[For the engineer: You have read that there is no such thing as "RMS power." Technically, you are right. However, over the years the term, regarding audio gear, has come to be applied to the measurement technique outlined above, so we use that language here, rather than terminology with which the customer is unfamiliar. Yes, the computation is mathematically an integral of the instantaneous power.]
An Explanation of RMS Power Measurement
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Power is simply the product of RMS Volts and RMS Amps, and the resulting figure is 'power'. Not 'RMS Power' - or any of the insane derivatives described above - just 'power'.
http://sound.westhost.com/power.htm
[ 本帖最後由 ciel 於 2009-9-13 17:00 編輯 ]