技術文章

真有效值，為什么對鉗表這么重要？

2022/05/22

在選擇鉗表的時候，最常聽到的問題大多是“精度怎樣“，”準不準“。影響鉗表準確性的因素很多，設計/做工、帶寬、頻率響應、包括是否選擇了適合的量程，均會對讀數造成影響。然而所有這些因素中，最重要的因素之一，便是真有效值測量，特別是對電氣設備種類繁多，電氣環境復雜的工業類用戶。非真有效值，也就是平均值響應的儀表，主要是針對標準工頻的正弦波的測量。常見的實現原理，是將測得的算數平均值讀數x1.1，轉化成正弦波的‘有效值‘讀數。在電氣化環境比較單純的環境，這是完全沒問題的，比如樓宇物業等。而更為廣泛的工業環境，特別是越來越多的變頻、整流器、逆變器等設備的使用，實際的波形越來越多樣化，甚至引入了越來越多的高頻噪聲，因此要準確測量，真有效值成為其中最重要的因素之一。我們來看一看如下的示意圖就秒懂了：提到噪聲或著諧波，不得不說另外一個重要的概念：低通濾波器（LPF）。言下之意，只有低頻電流電壓才能被測算，高頻的部分就會被截至不予計算?？梢哉f，只有具備了低通濾波的真有效值鉗表，才是真正有價值的‘真有效值‘。福祿克真有效值鉗表，全系真有效值鉗表*均配備800-900Hz低通濾波器，部分型號比如Fluke 369/368，安博ACD-14 PRO更是配備了60~70Hz截至的工頻低通濾波器（BP）（* 僅F-323， T6系列未配置）。鑒于真有效值對鉗表如此重要福祿克在今年特別推出了F325/324/323系列400A真有效值鉗表...

Fluke DSX-5000恢復出廠設置

2021/12/15

WARNING: This will delete ALL results and settings, there is no way to undo this.需要特別提醒的是：恢復過程當中將會導致所有的儀器設置和原來內置的測試報告均將丟失，并且這不是一個可逆的操作過程。This feature is for rental companies and locations where data is considered sensitive. It will not wipe out any information on a thumb drive attached to the Versiv (TFS) unit. If you have access to YouTube, you can watch how to do it here.Tap Tools followed by Memory Status. Touch the parts of the screen in the order shown below:You will then see a Restore Defaults button appear.Tap this for a final warning about doing this:The Versiv (TFS) will then play a tune and reboot....

為什么熱像儀會發出“咔咔” 聲？什么是自動校準？

2021/12/08

儀器內部發出“咔咔”聲是熱像儀自動校準引起的，通常發生在熱像儀快速移動；剛開機。自校原因：熱像儀會根據環境溫度變化，自動調整以抵消該變化對探測器準確性的影響，該過程一般持續2~3 秒，屏幕出現停滯并顯示“正在校準”。...

福祿克DTX-1800測試報告ACR-N顯示不適用N/A，而不是通過PASS

2021/11/22

福祿克DTX-1800測試報告中ACR-N顯示N/A，而不是PASS或者Fail，如下圖所示：（在Linkware軟件測試報告中的其他設備同理）如果你正在測試任何ANSI/TIA標準，你將會總是看到N/A出現在ACR-N測試指標欄目里面，因為ACN-N不是ANSI/TIA要求測試參數。但是因為許多客戶比較關注ACR-N這個指標，所以福祿克在測試的時候，會測試這個參數，并且標注出來，為了特別工程師的需求。值得一提的是ISO/IEC標準是需要測試ACR-N的。ISO/IEC標準測試出現N/A的時候，一般是使用永久鏈路進行測試時候，并且插入損耗小于4db。通道測試就不會?？偨Y：這個沒有對不對，你的設備（DTX-1800）測試只是根據你選擇的標準來判斷的?？傮wPASS就是合格。...

4db原則（法則）-英文原文 -福祿克DSX2-8000/DTX-1800

2021/11/19

A YouTube video explaining how this this works is also?available from here.This is applicable to the following cabling standards only:ISO/IEC 11801EN 50173Aus/NZJISWhen?the Insertion Loss is less than 4.0 dB at the frequency point where the measurement is made, then the measurement is ignored and not uated against the selected Test Limit/Cabling Standard in the DTX CableAnalyzer. This is often referred to as the 4 dB rule. It is not applied in the North American TIA Cabling Standards. Only certain test parameters and configurations will have the 4 dB rule. The tables below indicate which link? definitions and test parameters have the 4 dB rule applied to them. As an aid, the other rules are also listed.On a?short link, the Insertion Loss may never reach 4.0 dB. If that were to happen, then the entire measurement would be?ignored, or as the cabling standards phrase it; “recorded for information only”. If this were to happen with your DTX CableAnalyzer, you would see an “i” appear next to the summary result for that test parameter. In LinkWare software, the result would be recorded with “N/A’. An example is shown below:Concern is normally caused when the result has a negative margin. In this example we see the NEXT margin was -9.7 dB. A?negative margin is normally associated with a FAIL, but because the entire link never exceeded 4.0 dB Insertion Loss, it’s not a FAIL. Further?confusion lies in that the North American ANSI/TIA/-568-C.0 cabling standard does not have this 4 dB rule. If you were to test the same link above?with the same DTX CableAnalyzer, but using the North American Standard TIA Cat 5e Perm. Link, your result would be a FAIL.Please make sure you?have agreed in a Test Limit, in writing, before the project starts.Let’s review in detail how this works by looking at another example test result on the DTX CableAnalyzer.An ISO11801 PL Max Class D AUTOTEST was run on a short 6.0 m installed link, giving the following result:Looks normal. Let’s take a look at the NEXT result in a little more detail:You will observe that?the limit line has two colors, black and red. The cabling standards do not require the cable tester manufacturer to display where the 4 dB rule is implemented to the user, only that it is implemented. However, the DTX CableAnalyzer will indicate where the 4 dB rule has been implemented by changing the color of the limit line. If the?limit line is black,?the Insertion Loss was less than 4.0 dB. If?the limit line is red,?the Insertion Loss was 4.0 dB or greater. So for this Pair 1,2-4,5 the NEXT is not uated below 84.8 MHz. Let’s take a quick look at the Insertion Loss for Pair 4,5:As you can see, the Insertion Loss reached 4.0 dB at 84.8 MHz, as previously indicated in the NEXT Pair 1,2-4,5 graph above. NEXT contains two pairs. So which Insertion Loss pair do we use to implement the 4 dB rule? The disturbed pair is used for uation purposes. So if the worst case NEXT Pair was 1,2-7,8 then the?DTX CableAnalyzer would use the Insertion Loss values from Pair 7,8 to determine where the 4 dB rule is implemented.As previously mentioned, if the link is particularly short, then the Insertion Loss may never reach 4.0 dB and the entire NEXT result is “ignored”. Let’s take a closer look at the first example where the test result was:Looking at the worst case NEXT result, we see the entire limit line is black, suggesting that the Insertion Loss for Pair 4,5 never reached 4.0 dB:Looking at the Insertion Loss for Pair 4,5:We see that the Insertion did indeed never reach 4.0 dB, so the entire measurement is not uated against the limit line (ignored) and recorded as “i” Information Only. If this result was downloaded to LinkWare Software, the report would show N/A against this measurement:No further action is required by the installer. This is a valid standards compliant result....

12dB原則（法則） – 英文原文DSX2-8000/DTX-1800

2021/11/10

In the DSX-5000 CableAnalyzer, this is implemented automatically. If you test to either “ISO11801 Class Ea Channel” or “ISO11801 Class?PL2 Class Ea” and the insertion loss measurement is less than 12 dB at 450 MHz, a relaxed?NEXT limit may be applied. It is not possible to change PASS/FAIL limits in a field tester based on the measured result of a parameter. Compliance with ISO/IEC 11801 Class EA?requirements can be verified using the DTX CableAnalyzer in one of two ways: by obtaining a PASS condition using the regular “ISO11801 Channel Class Ea” or ”ISO11801 PL2 Class Ea” test option, orby obtaining a PASS condition using an alternate “ISO11801 Chan Class Ea Low IL” or “ISO11801 PL2 Class Ea Low IL” option; if a PASS* conditions applies to insertion loss, the true result should be a PASS, as explained in the following.ISO/IEC 11802:2002 Amendment 2 (Published April 2010) – Table A.5 “For Configurations PL1, PL2, and CP1, whenever the class EA?permanent link insertion loss at 450 MHz is less than 12 dB, subtract the term 1,4((f – 450)/50) to the equation stated above for the range of 450 MHz to 500 MHz.” ANSI/TIA-568-C.2 (Published August 2009) There is no such rule/requirement in this North American Standard for Category 6A. Reality check It is very unlikely that implementing the “12 dB rule” is going to turn your failing NEXT and PS NEXT results into a PASS. That’s because the NEXT limit is relaxed between 450 MHz and 500 MHz only, and not by much. Let’s take an example:Tested to “ISO11801 PL2 Class Ea”Tested to “ISO11801 PL2 Class Ea Low IL”It did not change the outcome of the test result, because the failing NEXT was not between 450 MHz and 500 MHz. This may be better explained using an animation:Known issue in previous DTX code The “ISO ClassEa Ch AMD1 Low IL” and “ISO ClassEa PL2 25N1599?Lo IL” test options in the DTX had an insertion loss limit of 12 dB at 450 MHz to prevent the user from incorrectly applying the “12 dB rule” detailed previously. The DTX CableAnalyzer (Version 1.36 limits) had an insertion loss limit that has a step response at 450 MHz as indicated below:This could result in a measurement incorrectly assigning a FAIL for the insertion loss parameter. It’s incorrect because the existing limit for insertion loss still applies; the 12 dB is only used for assessing whether the relaxed NEXT limit should be applied. As a result, we have changed the limit for insertion loss in the DTX CableAnalyzer and LinkWare software. The above result will now look like:The change indicated was incorporated into the DTX CableAnalyzer Software Version 2.22 and LinkWare 6.0 releases. If the AUTOTEST fails now, it’s because it failed to meet the 12 dB insertion loss requirement at 450 MHz, indicating that this test option cannot be used to achieve a PASS result for the Class EA?channel. It is possible for the DTX CableAnalyzer to report a PASS* for insertion loss @ 450 MHz if the measured insertion loss at 450 MHz is closer to 12 dB than the specified accuracy of the DTX CableAnalyzer. This PASS* for insertion loss?indicates that the DTX CableAnalyzer cannot determine within its measurement accuracy whether the relaxed NEXT and PS NEXT limits are applicable. It does not necessarily indicate that the measured insertion loss is within the measurement uncertainty of the limits for insertion loss that is applicable to ISO/IEC 11801 Class EA?cabling. If necessary, the true insertion loss performance of the cabling can be verified using the regular “ISO11801 Channel Class Ea” and “ISO11801 PL2 ClassEa”?test options, and observing the test result for insertion loss. If this result does not contain a PASS* result for insertion loss, the PASS* for insertion loss of the ISO11801 Chan ClassEa?Low IL test, technically speaking, should be a PASS and not PASS*. This is a limitation of the code in the DTX CableAnalyzer. In conclusion: The overall result of an ISO/IEC 11801 Class EA?test should be as follows:If either the “ISO11801Channel Class Ea” or “ISO11801Chan Class Ea Low IL” test shows a pass, the result is a PASS.If either the?”ISO11801 PL2?ClassEa” or “ISO11801 PL2 ClassEa Low IL”?test shows a pass, the result is a PASS.If the “ISO11801Chan Class Ea Low IL” or “ISO11801 PL2 ClassEa Low IL”?test shows a PASS* that is caused by the result for insertion loss only, the result of the “ISO11801Chan Class Ea Low IL” or “ISO11801 PL2 ClassEa Low IL”?should be reviewed for insertion loss only; if this result is a PASS, the result of the “ISO11801Chan Class Ea Low IL” or “ISO11801 PL2 ClassEa Low IL” test can be considered to be PASS (the ‘*” is not applicable)....

3dB原則(法則) – DTX-1800/DSX2-8000 CableAnalyzer

2021/10/31

A YouTube video explaining how this this works is also?available from here.This is applicable to ALL test limits in the DTX CableAnalyzer where a Return Loss measurement is made.When?the Insertion Loss is less than 3.0 dB at the frequency point where the measurement is made, then the Return Loss measurement is ignored and not uated against the selected Test Limit/Cabling Standard in the DTX CableAnalyzer.This is often referred to as the?3 dB rule.It applies to ALL cabling standards/test limits in the DTX CableAnalyzer.On a short?link,the Insertion Loss may never reach 3.0 dB.If that were to happen, then the entire measurement would be?ignored, or as the cabling standards phrase it; “recorded for information only”.If this were to happen with your DTX CableAnalyzer, you would see an “i” appear next to the summary result for that test parameter.In LinkWare software, the result would be recorded with “N/A’.An example is shown below:Concern is normally caused when the result has a negative margin.In this example we see the Return Loss margin was -2.2. A?negative margin is normally associated with a FAIL, but because the entire link never exceeded 3.0 dB Insertion Loss, it is not a FAIL.Let’s review in detail how this works by looking at another example test result.A TIA Cat 5e Perm.Link AUTOTEST was run on a 29.0 m installed link, giving the following result:Looks normal – very nice margins.Let’s take a look at the Return Loss result in a little more detail:You will observe that?the limit line has two colors, black and red.The cabling standards do not require the cable tester manufacturer to display where the?3 dB rule is implemented to the user, only that it is implemented.However, the DTX CableAnalyzer will indicate where the 3 dB rule has been implemented by changing the color of the limit line.If the?limit line is black, it?indicates that the Insertion Loss was less than 3.0 dB.If the?limit line is red, the Insertion Loss was 3.0 dB or greater.So for this Pair 3,6 the Return Loss?is not uated below 29.3 MHz. Let’s take a quick look at the Insertion Loss for Pair 3,6:As you can see, the Insertion Loss reached 3.0 dB at 29.3 MHz, as previously indicated in the Return Loss Pair 3,6 graph above.It’s an interesting rule, because if it were not in place, our margin for the above result would reduce from 10.2 dB to 9.0 dB:As previously mentioned, if the link is particularly short, then the Insertion Loss may never reach 3.0 dB and the entire Return Loss?result is “ignored”.Let’s take a closer look at the first example where the test result was:Looking at the worst case Return Loss result, we see the entire limit line is black, suggesting that the Insertion Loss for Pair?3,6 never reached 3.0 dB:Looking at the Insertion Loss for Pair 3,6:We see that the Insertion did indeed never reach 3.0 dB, so the entire measurement is not uated against the limit line (ignored) and recorded as “i” Information Only.If this result was downloaded to LinkWare Software, the report would show N/A against this measurement:No further action is required by the installer.This is a valid standards compliant result....

Fluke DTX系列中測試結果中星號的*的解釋

2021/10/28

FLUKE DTX系列測試報告中為什么會出現*號？以及同樣的線材在不同的測試平臺上的結果為什么會有不一致的現象？請看下面文章：通常如果測試的最差余量不幸落在了儀器的測試精度范圍之外,在設備的測試界面上我們就會發現會多出(*).號標志。這恰好是基于ANSI/TIA/EIA-568-BandIEC61935-1的標準要求來做的. 讓我們來看看在什么頻率點出現1.9db的余量值為了更好的便于理解，在下附圖中我們將標準極限值的用紅色線條標識出來.用兩條黑色的線條來標識出儀器的精度判別范圍,其中黃色區域將是精度無法識別的區間.在所有的測試結果結果當中，如果不幸有測試的最差余量值落在了這個區間，那么將會有(*)予以明確標示.這對于理解在頻率域范圍內的波形幅度變化是非常重要的。我們選擇線對Pair3,6-4,5繪制出下圖:剛好在這個無法判別的精度區間,因此*會出現在最終的測試結果當中?？偨Y：通常如果出現*號的標示，不論是通過或者不通過，我們認為當前的測試結果都是超出了機器的判別精度范圍之外，因此我們需要就相同的線材進行多次測試，驗證經過多次測試結果是否一致？或者換一下接頭，把線材調一個頭測試一下。另外，為什么不同儀器會有不同值。以DTX-1800為例：有的插入損耗0.1的結果上面是標注有*號的，標有*號的意味著是在精度范圍之外，機器已經無法判斷出測試結果究竟是不是通過，有些它就會以“失敗”來判斷出此次測試結果；同樣，另外一臺DTX-1800的機器上，測試結果是以通過來標識的，它的插入損耗為0.9也是標注有*號的，也就是說DTX-1800這臺機器它的某些測試指標上下容許有正負1+1%的上下浮動誤差。...

目錄

首頁

品牌中心+

Fluke/福祿克工業儀器+

紅外熱像儀+

紅外測溫儀+

數字萬用表+

數字鉗形表+

絕緣電阻測試儀+

接地電阻測試儀+

示波器+

蓄電池電阻分析儀+

電能質量分析儀+

漏電開關測試儀+

安規測試儀+

過程校準器+

回路校驗儀+

壓力校驗儀+

溫度校驗儀+

測距儀+

粒子計數器+

多功能環境測試儀+

照度計+

空氣質量檢測儀+

風速儀+

噪音計+

光度計+

激光對中儀+

激光水平儀+

測振儀+

數據采集器+

醫療測試+

配件/工具+

NetAlly（原NetScout）+

有線網絡測試儀+

無線網絡測試儀+

有線+無線網絡測試儀+

Fluke Networks/福祿克網絡儀器+

網線測試儀+

網絡測試儀+

光纖測試儀+

配件/工具+

FLIR/菲力爾+

紅外熱像儀+

Raytek/雷泰儀器+

紅外測溫儀+

在線式紅外測溫儀+

KEYSIGHT/是德（原Agilent/安捷倫）+

數字萬用表+

電源+

示波器+

VIAVI（原JDSU）+

光時域反射儀（OTDR）+

光功率計+

光源+

EXFO（加拿大EXFO）+

光時域反射儀（OTDR）+

光功率計+

光源+

Tektronix/泰克+

示波器+

萬用表+

配件+

Megger/梅凱（梅格）+

絕緣電阻測試儀+

繼電保護測試儀+

低電阻測試儀+

接觸電阻測試儀+

接地電阻測試儀+

FOTRIC/飛礎科+

紅外熱像儀+

配件+

KYORITSU/共立（克列茨）+

絕緣電阻測試儀+

Fujikura/藤倉+

光纖熔接機+

YOKOGAWA/橫河+

光時域反射儀（OTDR）+

法國C.A+

電能質量分析儀+