EMI测试报告解释

第13页：测试方法之EMI防辐射检测

20xx年09月03日11:13

EMI测试报告解释

EMI测试报告解释

将待测的机箱摆放在中央的木质桌子上

EMI测试报告解释

开机系统运行 检测开始

EMI测试报告解释

■ 如何来认读EMI测试报告

这是一份EMI测试报道，我们之后的产品介绍部分也都将以测试报告来呈现，因此为了便于读者认读报告数据，我们先来进行一下解释说明。这样一份EMI的检测报告，如图上所注有五个必须要认清的部分：

报告中五大看点

EMI测试报告解释

A：此处箭头所指是IEEE国际电子工程协会立法规定的EMI标准线，也就是说如若检测出超出此线，就视为EMI超标。

B：此处标红的线要低于IEEE国际标准，属于富士康华南检测室基于IEC标准下进行更严格的标记。关于EMI测试标准，我国仅有政府直属机关才有检测资格，而我们此次的华南检测室是基于国际IEC标准，为更加直观的介绍标准的划分，我们特以下图来进行说明。

C：此处标明的单词VERTICAL，是指天线处于垂直状态时的测试数据，EMI测试过程中，天线会分别处于水平和垂直两种状态下进行测试，我们的测试报告也分为两个部分，此处“VERTICAL”为垂直测试数据，“HORIZONTAL”则为水平

测试数据。

D：此处标明的“OverLimit”数据，是我们针对各产品进行衡量比较的，也就是说如果OverLimit这一列的数据有超出标准线的，就视为不合格。换句话说，我们应该看到如果OverLimit呈负值，而且越小，其EMI成绩则越出色。

E：在30-1000MHz范围内，系统基本运行稳定，取此频率段的数据为结果，而每款机箱都会提供10组测试成绩，以OverLimit最大值来衡量各机箱EMI之间的差异。

 

第二篇：Mesure the Resistance via the Wheastone Bridge 电桥法测电阻 实验报告 英语

Measure the Resistance via the Wheastone Bridge

1.The purpose:

i.              To understand the principle and characteristics of the Wheatstone bridge.

ii.              To understand the concept of sensitivity of bridge.

iii.              Learn the “exchange measure method”, with which to eliminate the system error.

2.The apparatus:

   Unknown resistances; DC power supply; galvanometer; resistor box; variable resistor; switch and other electrical components; electrical bridge.

3.Theories:                                                    

1)The principle and the structure of the Wheatstone bridge

22.jpg 

When UC=UD

RX=

2)The sensitivity of the Wheatstone bridge

Because of the sensitivity of the galvanometer is limited, the current through the galvanometer is not truly zero, and the galvanometer cannot efficiently measure it.

The sensitivity of the bridge is defined as the ratio between the deflection of the galvanometer, Dd, and the corresponding relative value of R0.

S=

3)The “exchange measure method”.

Exchange the positions of R1 and R2, or R0 and Rx, and adjusting R0 to R0 ¢, the bridge can get a new balanced state，and               RX= 

Combine this equation with RX=, we can get:

RX=

This equation has nothing to do with R1 and R2. In this way we can make the error only relate to the instrument error of R0, which is the instrument error of resistor box.

4.The procedures:

1)     Use simply constructed bridge to measure the metal film resistor.

Connect the circuit and measure the resistance then exchange R0 and RX measure the resistance again.

The key points:

         i.              Find the balance point.

       ii.              Measure the sensitivity of the bridge.

    iii.              Exchange R0 and RX measure the resistance again.

Error analysis:

The uncertainty of R0:

apparatus=R0 apparatus=0.1%Ro+0.005(K+1)

The error caused by the sensitivity of the bridge is:

Δ=R0  (S is the sensitivity of the galvanometer)

URo=

The relative uncertainty of RX is:

= (N=1.0)

2)     Use box-bridge to measure the resistance.

         i.              Make the reading of galvanometer back to “0” via mechanical method.

       ii.              Open K, press G button, adjust M and keep the galvanometer balance.

    iii.              Connect RX with X.

     iv.              Adjust the system and record the resistance R0 which make the galvanometer balance.

Error analysis:

The limit of fundamental error is:

Elim=α%(NRo+)

The error caused by the sensitivity of the bridge box is:

Δ=NR0

The relative uncertainty of RX is:

URx=

5.Data processing:

TEST ONE.

Use simply constructed bridge to measure the metal film resistor.

a)      For U=8V Rinner=100Ω

RX==Ω=498.35Ω

S===277

The uncertainty of R0:

apparatus=R0 apparatus=0.1%Ro+0.005(K+1)

=0.1%497.7Ω+0.005(4+1)=0.5227Ω

The error caused by the sensitivity of the bridge is:

Δ=R0=497.7Ω=0.3594Ω

URo=

==0.63434Ω

The relative uncertainty of RX is:

=

==9.0123x10-4

==9.0123x10-4x498.35Ω=0.45Ω

RX=498.350.45Ω

b)      For U=8V Rinner=2500Ω

RX==Ω=499.05Ω

S===53.6

The uncertainty of R0:

apparatus=R0 apparatus=0.1%Ro+0.005(K+1)

=0.1%498.1Ω+0.005(4+1)=0.5231Ω

The error caused by the sensitivity of the bridge is:

Δ=R0=498.1Ω=1.859Ω

URo=

==1.9312Ω

The relative uncertainty of RX is:

=

==2.7415x10-3

==2.7415x10-3x499.05Ω=1.4Ω

RX=499.01.4Ω

c)       For U=4V Rinner=100Ω

RX==Ω=498.85Ω

S===135

The uncertainty of R0:

apparatus=R0 apparatus=0.1%Ro+0.005(K+1)

=0.1%497.7Ω+0.005(4+1)=0.5227Ω

The error caused by the sensitivity of the bridge is:

Δ=R0=497.7Ω=0.7373Ω

URo=

==0.90378Ω

The relative uncertainty of RX is:

=

==1.2840x10-3

==1.2840x10-3x498.85Ω=0.6Ω

RX=498.80.6Ω

d)      For U=4V Rinner=2500Ω

RX==Ω=499.15Ω

S===31.1

The uncertainty of R0:

apparatus=R0 apparatus=0.1%Ro+0.005(K+1)

=0.1%498.2Ω+0.005(4+1)=0.5232Ω

The error caused by the sensitivity of the bridge is:

Δ=R0=498.2Ω=3.010Ω

URo=

==3.0551Ω

The relative uncertainty of RX is:

=

==4.3362x10-3

==4.3362x10-3x499.15Ω=2.2Ω

RX=499.22.2Ω

TEST TWO

Use box-bridge to measure the resistance.

A.      For resistor RX1

S===17.4x103

The limit of fundamental error is:

Elim=α%(NRo+)=0.1%x5120.4Ω+1Ω=6.1204Ω

The error caused by the sensitivity of the bridge box is:

Δ=NR0=1x5120.4Ωx=0.058855Ω

The relative uncertainty of RX is:

URx==

   =6Ω

RX=51206Ω

B.      For resistor RX2

S===26.9x103

The limit of fundamental error is:

Elim=α%(NRo+)=0.1%x10-1x4983.8Ω+0.1Ω

=0.59838Ω (=10000, and I get it from

Elim=α%(NRo+)=0+1)

The error caused by the sensitivity of the bridge box is:

Δ=NR0=10-1x4983.8Ωx=0.0037054Ω

The relative uncertainty of RX is:

URx=

=

   =0.6

RX=498.46Ω

Discussion:

In the 1st test, “use simply constructed bridge to measure the metal film resistor”. As we can see that the “exchange measure method” eliminated the error which caused by the uncertainty of R1 and R2.Thus the main error in this experiment is the instrumental error of the resistor box (URo). The instrumental error is mainly caused byR0 apparatus. The error caused by the sensitivity of the bridge (Δ) also contributes to the error URo.

   From the form, we can get that R0 apparatus plays an important role in the error when the inner resistance of the galvanometer is relative small or the voltage of the power is relative larger. On the other hand, the error caused by the sensitivity of the bridge (Δ) is the main error when the inner resistance of the galvanometer is big or the voltage of the power is small.

In the 2nd test, “use box-bridge to measure the resistance”.

The main error is the fundamental error limit (Elim) and the error caused by the sensitivity of the bridge box (Δ).

   We can easily get that the main error in “use box-bridge to measure the resistance” is the fundamental error limit (Elim). And the error caused by the sensitivity of the bridge box (Δ) is so small that it can be neglected.

6.Conclusions:

From this experiment we can get that:

In the 1st test, “use simply constructed bridge to measure the metal film resistor”

In the 2nd test, “use box-bridge to measure the resistance”.

What’s more, when we use simply constructed bridge to measure the resistance, we’d better use a power supply with relative high voltage and also we should use a galvanometer with small inner resistance.

   While we use the box bridge, the error mainly relate to Elim, and Elim=α%(NRo+), thus it is better to measure small resistor with box bridge.

相关推荐

专栏推荐