【文章內(nèi)容簡介】 ectrical quantities ,specially the current ,and sent to the A/D converters . 如下所示的物理量的常被用于測試和測量技術(shù),第2通常被稱為電子數(shù)量和其他通常被稱為電氣參數(shù)。通常傳感器接收信息清單QUM測量(下),把它轉(zhuǎn)化成電氣參數(shù)的變化或電氣潛力,通常會條件,然后轉(zhuǎn)化為電氣數(shù)量,特別是當(dāng)前的眾長老、就差人到A / D耐.Electrical potential difference 電氣電位差The primary standard for electrical potential difference used to be provided by an electrochemical standard cell (the Weston standard cell ).The voltage of a Weston cell is approximately V at 20`C,with an inaccuracy of 3X10^6 under optimal conditions. Optimal conditions means a variation of temperature less than 10^3 K, no load, no vibrations or jolting . The cell must remain in an upright position. A Weston standard cell has a very long thermal aftereffect. After the cell has been heated to 30`C it can take 6 months before it is totally stable within V of the original value at 20degrees .Furthermore ,a Weston cell will age , resulting in an increase in the internal resistance (R1~5001000歐)，and a small decrease of a few uV in the output voltage (during the first years ).電氣的基本標(biāo)準(zhǔn)的用于電位差由電化學(xué)標(biāo)準(zhǔn)電池的(韋斯頓標(biāo)準(zhǔn)電池電壓成),39。C的精度,在優(yōu)化的分析條件下,3X10 ^。最優(yōu)性條件溫度的變化是指小于10 ^ 3鉀、空載,沒有振動或震動。細(xì)胞必須保持在一個垂直位置。一個韋斯頓標(biāo)準(zhǔn)電池的有很長的熱aftereffect。在細(xì)胞被加熱到3.Electrical current 電流lectrical current is standardized by measurement with an instrument called a ‘current balance’. This device measures the electromagnetic force between two current carrying coils (one fixed ,one moving ) by balancing it with the force of gravity ,acting on a known mass . The force between the coils is given by F=I^2dM/dx , in which M is the known mutual induction of the coils and x is the known distance between them . The differential quotient dM/dx is determined by known geometry of the coils .通過測量規(guī)范激勵激光器阻抗電流被稱為“用鐵器當(dāng)期資產(chǎn)”。這種裝置措施電磁力在兩個電流負(fù)載線圈(一個固定的,一個運(yùn)動)平衡與重力的作用下,行動在一個已知的質(zhì)量。線圈間的力進(jìn)行女=我^ 2dM / dx,M是已知的相互感應(yīng)的線圈與x是已知的間距。鑒別商dM /遠(yuǎn)程接收由已知的幾何學(xué)的線圈。Electrical resistance 電阻Standards of electrical resistance are resistors wound of special alloy wire giving a minimal temperature effect .An example of such an alloy is evanohm , consisting of 74% nickel ,20%chromium and 6%aluminium and iron . This alloy is frequently used for high resistance standards (10kQ). For low resistance values (1Q) manganine (86%Cu ,12%Mn ,2%Ni ) or constantan (54%Cu ,45%Ni ,1%Mn ) is often used .Higher –order resistance standards are kept at very accurately stabilised temperature by thermostats . evanohm是一種合金,由74%鎳、20%chromium和6%aluminium與鐵。這種合金是經(jīng)常用于高阻標(biāo)準(zhǔn)(10kQ)。低阻值(第manganine(86%Cu,12%Mn),2%Ni)或constantan(54%Cu,45%Ni,1%Mn) order電阻標(biāo)準(zhǔn)保持非常準(zhǔn)確穩(wěn)定溫度溫控器。Capacitance 電容It is possible to construct a capacitor from four coaxial cylinders , whose capacitance only depends on the length of the cylinders . Such a capacitor is particularly suitable as a standard of capacitance , since only the length has to be determined accurately . With the aid of optical interferometry this can be done extremely accurately . These socalled ThompsonLampard cylinder capacitors can achieve an inaccuracy of less than 10^8. 它可以構(gòu)建電容器的從四個同軸鋼瓶,電容僅憑長度的汽缸。這樣的電容器是特別適合標(biāo)準(zhǔn)的電容,因?yàn)橹挥虚L度必須提供準(zhǔn)確的參數(shù)。與援助的光學(xué)干涉技術(shù)能夠依此作成,非常準(zhǔn)確。這些所謂的ThompsonLampard缸電容可以達(dá)到不小于10 ^ 8。 A disadvantage ,however ,is the fact that the capacitance is small (approximately per metre ). For lowerorder standards other configurations of electrodes are used ,which provide larger capacitance values (10~1000pF),but also e larger uncertainties .然而,一個不利條件的人來說,(大約每米)。其它結(jié)構(gòu)的標(biāo)準(zhǔn)為查核使用電極,提供較大的電容值(10 ~ 1000pF),但也來了更大的不確定性。Inductance 電感Accurate standards of inductance are difficult to realise . This is caused by the many parameters that determine the relatively plex of a coil ,all of which influence the accuracy of the inductor .Furthermore ,power losses occur ,due to wire resistance ,proximately effects and eddy currents ,which add to inaccuracy ,Currently a available standards of inductance have an inaccuracy of about 10^5 .精確的標(biāo)準(zhǔn)的電感難以想象。這是由于很多參數(shù),確定的較為復(fù)雜的線圈,影響電感的準(zhǔn)確性發(fā)生,由于線電阻、遲延直接影響和渦流、增加到不準(zhǔn)確,目前提供標(biāo)準(zhǔn)的電感有一個不大約10 ^ 5。Frequency 頻率 The standard of frequency is based on quantum mechanical effect that electrons in an atom can only occupy one of a limited number of energy levels .If an electron jumps to a higher or a lower energy level ,the difference in energy E of the photon that is absorbed or a emitted , respectively ,is related to the frequency of the photon by the expression E=h atoms are irradiated with electromagnetic energy of frequency f0,many electrons will pass to higher energy levels .標(biāo)準(zhǔn)的頻率是基于量子力學(xué)效應(yīng)原子電子之一只能占據(jù)數(shù)量有限的能量水平,如果一個電子的價格漲到一個更高的或較低的能量水平,不同的能源E被吸收的光,分別或發(fā)出有關(guān)光子的頻率的表情E = h f0 . 當(dāng)原子電磁能量下的頻率f0,許多電子將通過更高能量水平。 of nonphysical quantities 測量非物理性的數(shù)量 Nonphysical quantities found in nontechnical fields are very difficult or even impossible to measure, mainly because they are part of very plex systems (people, organizations ,societie