Megger MFT1741 Bedienungsanleitung

MFT1741 and MFT1845

Multifunction Testers

MFT Addendum

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User Guide Addendum - MFT1741-MFT1845 www.megger.com 2

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User Guide Addendum - MFT1741-MFT1845 www.megger.com

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Contents

EN - Addendum to Section 7.0 4

CN - 对第 7.0 节的增补 9

DE - Nachtrag zu Abschnitt 7.0 14

EL - Προσάρτημα στην Ενότητα 7.0 19

ES - Apéndice para la sección 7.0 24

FR - Addendum à la section 7.0 29

IT - Appendice alla Sezione 7.0 34

NL - Addendum bij paragraaf 7.0 39

PL - Uzupełnienie do rozdziału 7.0 44

SK - Dodatok k časti 7.0 49

SV - Tillägg till avsnitt 7.0 54

ZH - 第 7.0 章的增補 59

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Addendum to Section 7.0

Supplementary information for the MFT1741 and

MFT1845 User Guide

Applies to: Loop Impedance Tests (MFT1741 and MFT1845

only).

New feature: Con󰘰dence Meter (Patent Applied For) for non-trip

(3Lo) loop impedance tests.

Display information:

Con󰄈dence Meter Function (Patent Applied For)

Variable test results in a Loop Impedance test are usually

a result of electrical noise on the circuit during the test. The

Con󰘰dence Meter analyses this electrical noise and, if necessary,

automatically extends the duration of the test to arrive at an

accurate 󰘰gure (as per the instruments stated accuracy).

The analogue arc is used to indicate the degree of con󰘰dence in

the accuracy of a measurement.

Figure 1. Instrument Display

Con󰘰dence

meter

3Lo (3 wire

non-trip)

Mode indicator

Noise detected

Standard non-trip loop

impedance mode test

indicator

Non-trip loop impedance test

mode for circuits with Type B

RCD

Test “in progress”

warning

Units of

measurement

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During a test the analogue arc will reduce as the degree of

con󰘰dence in the measurement increases. As the in󰘱uence of

electrical noise on the measurement is removed the analogue

arc reduces down to one element. At this point the test stops and

a 󰘰nal result is shown.

The arc may 󰘱uctuate during a test and the shown digital value

will change as the Con󰘰dence Meter analyses the electrical noise

and corrects the value.

3Lo Loop Impedance Measurement

Note: Test leads should not be disconnected during a test, as the

sudden interruption of the test current could be detected by an

RCD as a leakage fault and cause a trip. If this is considered to

be potentially inconvenient or hazardous, change 3Lo from AC/A

to Bmode. This will reduce the risk of the RCD tripping.

Important: It is impossible to guarantee that an RCD will not

trip as the RCD may be out of speci󰘰cation, subject to additional

external in󰘱uences, incorrectly connected or faulty. In this

instance alternative methods to test the circuit characteristics are

recommended, for example, the R2 method.

1. Select L-PE.

2. Connect the Live, Neural and Earth test leads of the

MFT to a live circuit. The display will show the standard

warning screen.

Figure 2. Analogue Arc

Initial valueStart Analysing noise Finished

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The display will show , which indicates the suitability

for use on circuits protected by a Type AC or a Type A RCD, or

RCBO.

If the RCD on the circuit is a Type B, press and hold until

the display shows (Type B RCD).

Note: If unsure of the RCD type use Type B setting.

3. Press TEST. The display will show the start of a Loop

Impedance con󰘰dence test, followed by an initial value of

loop impedance:

Figure 3.

3Lo Connection Options

Figure 4. Live Circuit

Warning Screen

MCB RCD

CAT IV

300V

12-15V

1.2A

RCD

MCB

CAT IV

300V

12-15V

1.2A

> then >

Figure 5. Loop Impedance Test Start Screen

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Note: The test is not 󰘰nished until the analogue arc reduces to

one element, or the TEST button is pressed again.

4. If no noise is detected the analogue arc will reduce to a

single element and the display will show a completed test

result. The 󰘰nal value may vary slightly if very small levels

of noise were detected.

5. If electrical noise is detected, the instrument analyses

it continuously and the analogue arc will reduce as the

electrical noise is 󰘰ltered from the measurement. Even

if there is a lot of electrical noise, the con󰘰dence of the

measurement will improve with time and the analogue arc

will reduce, so that a 󰘰nal stable value will show at the

end.

(electrical noise symbol) will also show to indicate the

presence on electrical noise on the circuit.

If the electrical noise in the circuit varies the analogue arc may

󰘱uctuate until the test has completed and the analogue arc shows

a single element.

Figure 6. Final Result

Figure 7. Analogue Arc Fluctuation

Start Small noise

Momentarily

higher noise Complete

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Note: The maximum measurement time is three minutes. If

after three minutes there is still more than one element in the

analogue arc, the test will stop. More than one element shows

that the instrument has not achieved its desired con󰘰dence level

(electrical noise is high). The test is still valid, but with reduced

accuracy.

6. Press TEST at any time to stop the test. A digital test

result will show and the size of the analogue arc shows

the degree of con󰘰dence in the test result (smaller the

analogue arc = more con󰘰dence).

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对第 7.0 节的增补

MFT1741 和 MFT1845《用户指南》的补充资料

适用于：回路阻抗测试（仅限 MFT1741 和 MFT1845）。

新功能：准确性评估计（已申请专利），用于不跳闸的 (3Lo) 回路

阻抗测试。

显示信息:

准确性评估计功能（已申请专利）

回路阻抗测试中出现的测试结果波动现象通常是由于测试期间电路

中的干扰引起的。准确性评估计会分析此干扰，并在必要时自动延

长测试的持续时间，以获得一个精确的数值（按照仪器所声明的精

确度）。

图 1. 仪器显示

准确性评

估计

3Lo（3 线不

跳闸）模式指

示器

检测到干扰

标准的不跳闸回路阻抗

模式的测试指示器

不跳闸的回路阻抗测试模式，

适用于使用 B 型 RCD 的电路

测试“正在进行”

警告

测量单位

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准确性评估计采用了模拟表头来指示测量精确度的可信度。

在测试期间，模拟表头会随着测量中可信度的增加而缩小。当干

扰对测量的影响被去除时，模拟表头会缩小为一个刻度。此时测

试停止，并显示最终结果。

此模拟表头在测试期间可能会波动，所示的数字值会随着准确性

评估计对干扰的分析以及对该值的修正而变化。

3Lo 回路阻抗测量

备注: 测试引线在测试过程中不得断开，因为测试电流的突然中断

会被 RCD 视作发生了漏电故障并引起跳闸。如果认为这种情况会

带来潜在不便或危险，请将 3Lo 从 AC/A 切换到 B 模式。这样将

会减少 RCD 跳闸的风险。

重要事项: 由于其他外部影响因素、错误接线或故障的原因，导致

RCD 可能会检测到超出额定值的信号，因此无法保证 RCD 不会

跳闸。在这种情况下，建议采用备选方法来测试电路的特性，例

如 R2 方法。

1. 选择 L-PE。

2. 将 MFT 的火线、零线和接地测试引线连接到一个带电电

路。显示屏将显示标准的警告界面。

图 2. 模拟表头

初始值开始干扰分析中结束

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