EMI测试仪器的如何校准才能准确无误

jxwyzg

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   大家好，有个问题想请教下各位。
5 q3 B. r$ I7 ?1 U" u( P* G9 t  我们公司用的是R/S的EMI测试仪（一台V型网络和一台分析仪），按照说明书上说的进行自校，但是我用的同一个产品，连续测试出来的数据相差偏大。（第一次测试按照标准上稳定的时间，然后进行测试。第二次是等测试完成后过了两个小时然后同样按照标准再次测试）
" i! T6 o/ h' C5 X; S& z   我想知道的是，自校后测试如何使同一个产品测试出来的结果相差不大？
  
       请教高手解答！
            小弟先谢谢了！

wangjb

这也是我很想知道的问题

jxwyzg

嘿嘿。看来这个问题难倒很多高手了！

mypcb

可能需要你将问题点描述的更清楚一些:
5 v3 ~+ S  x* ]5 C$ C1.两次测试是否同一EUT,同一测试人员,同样的摆放位置?
2.两次测试的EUT是否预热时间相同?
, h. t+ s2 ?7 X+ _5 C, a- N3.两次测试过程中仪器有没有更改过参数?
4.仪器的自校是否将仪器界面左边"CAL"按键中记录校准补偿数据更改了
  比如说将10DB的衰减器补偿数据删除了?
5.是否你现在每次测试的结果都与第二次测试数据一致?
% h3 Y5 v) U$ z% J8 \
7 b9 i. k. ~+ a以上你描述一下可能大家更好来分析.....

jxwyzg

引用第3楼mypcb于2011-02-24 15:45发表的  :
  L/ x. d/ B% Q8 o3 Q可能需要你将问题点描述的更清楚一些:
/ _! A- j" ~! T% w: K1.两次测试是否同一EUT,同一测试人员,同样的摆放位置?
2.两次测试的EUT是否预热时间相同?
; Y% x" F6 b7 O2 K0 g! c4 I3.两次测试过程中仪器有没有更改过参数?
& ~: h, a) S4 v: ]# M; p4.仪器的自校是否将仪器界面左边"CAL"按键中记录校准补偿数据更改了
.......

   
2 U6 {1 [4 K/ f! R2 D        相同的仪器，相同的测试人员，相同的摆放位置，相同的预热时间，没有更改过任何软件设置。
这个问题难倒了很多高手啊，我也问过认证机构的工程是，他们解答不了，发了邮件过去给厂家，到现在还没有回复我。。。

kamleung

I have also used the R&S test receiver and LISN to have the EMC test. So far, the repeatability is within +/- 1.5 dB for the same test sample under the same test conditions (test mode, loading and placement). To know what has happen to your testing, would you mind telling us
/ e2 Z% G1 l  c) W. Q: l     - how much the data deviations are obtained in your tests
     - what kind of your product under test
) J& a4 k( }' m* ]" z4 t     - what running mode of your product is set during the test
     - what is the loading condition doe your product
' i! f# W* [5 i2 `     - what is the placement of your product on the test table
5 p( j& ]! ?  J: j' W$ m" v& x     - where the test is done (shielded room or somewhere else)

" w: c7 V2 {0 h4 hIf possible, may we have
     -  the drawings or photos of your test set-up (location of test receiver, LISN, test table and etc)
     -  the photos showing the placement of your product during the test
     -  the photo showing the power cord arrangement during the test

jxwyzg

测试的产品是节能灯。灯电压220V 频率 50HZ 功率30W  。 V型网络接的稳压源，220V电压，50HZ的频率，产品接入V型网络中。。。。。。。。。。
1 w5 x0 m& e+ Y  按照EN55015的标准，测试9K-30M这个段位，是在屏蔽房中进行测试
  产品放在木质的小桌子上，离地面40cm，里四周前面各80cm,桌子下方有铁板，且有接地。   灯放在标准的灯罩内（灯罩是铁做的，有接地）
   以上这些工作做好后，灯预热15分钟后开始测试，第一次测试在1M的段位上离限值有10dB的余量。第二次测试，以上方法不变，测试出来的1M的段位上离限值只有5dB的余量。
    因为R/S的仪器是采用打点方式来计算余量，我想知道的有两个问题。
  1：是不是我的测试方法有问题？
  2：R/S的打点计算余量是根据什么标准来判定结果的？
   求高手回答！

kamleung

Perhaps, the problem is not coming from the R&S test receiver. The lamp's data changes with the total amount of its working times. Therefore,  there are "Ageing", "Stabilization time" and "Statistical estimation" requirements in EN55015.

For energy saving lamp, the ageing time of a test sample is at least 100 hrs. The warm-up time is 30 mins before making the measurement. Was your test sample well prepared according to these two requirements?

) F8 J1 [4 K3 o" f  t% eFor R&S test receiver, it will use the PK mode to scan and search the peaks of data. Only the peaks above the user defined threshold will then be taken the formal measurements and compared against with the limits.

jxwyzg

测试的样品是要送TUV做认证的。
+ d" I$ g! ]/ J3 D3 Y因为我们公司的实验室是可以做目击测试，R/S的仪器也是和TUV的一个型号。担心的是怕我们测试出来的样品数据和TUV测试出来的数据相差偏大。
5 r/ V2 }+ _- r0 W. z3 y   灯都是按照标准来做的测试，测试前已经老化100h，待预热15分钟以后再开始测试。
1 d, x3 N1 F6 E, E: ?   如果灯没有什么问题的，其余问题是出在仪器上面？
0 A, l$ H5 G9 g  B   我想知道的是，R/S的仪器有没有取点限制之类的标准？（用的是EMC32测试软件，不是手动测试）

kamleung

As you are using the same test receiver as TUV, your equipment is reliable.

9 x& R. q1 y, W, a+ V$ o( HIn fact,  I just follow the ITS-HK method. ITS-HK is using the built-in feature of test receiver.  This feature is named as "Automatic Final Measurement with Threshold Scan" in the operating manual. The test receiver will have a fast prescan. If the measured level exceeds a limit line, or violates a margin defined for this line, the final measurement is performed. Hence, the number of readings is depending on the setting of margin. By using the equipment built-in feature, I have never used the R&S EMC32 Test software.
. ]4 W# s; g7 t- e# E4 r
The cabling of the conical housing also affects the data. Hence, you may check your test setup against with the requirements in EN55015. For details, pls read my attachment.
* U$ ]" L' ~: }5 |4 `5 H( C/ o: I
  E: u  A" C; A( Y+ A  YBy the way, TUV will get the witness test for your lamps. You need not worrying about so much.  TUV will point out the problems for you during his witness. For the CFL, you should test at least five samples and calculate the mean value and standard deviation to decide the EMC compliance.  That means a problem in a single lamp will not quite critical.