Insulation Measurements; Description Of The Measurement Principle - AEMC 6550 User Manual

When the external voltage exceeds 25V, the blinking (
NOTE: By pressing the DISPLAY button, the screen can be switched to a big numerical indication of the
input voltage and its bargraph.
The only errors possible in a voltage measurement are:
■
The frequency is outside the measurement range (see § 7.2.1)
■
The voltage is outside the measurement range (see § 7.2.1)

4.4 Insulation Measurements

Insulation measurements are made on objects that are de-energized.
This measurement varies greatly with the temperature and the relative humidity. It is
therefore essential to measure them with a separate device and to record them with the
insulation value.
%
The ambient temperature can be entered in the instrument and stored with the measure-
ment results.
The value of the test voltage is generally twice the voltage at which the object to be
tested is used, unless a standard stipulates otherwise.
For example, for a motor that operates on a 230V supply, the test will be performed at 500V.

4.4.1 Description of the Measurement Principle

The instrument generates a DC test voltage equal to the chosen nominal voltage VN between the + and - ter-
minals. More precisely, the value of this voltage depends on the resistance to be measured (see the curves of §
7.2.3). The instrument measures the voltage and the current between the two terminals and from them deduces
R=V/I.
The instrument measures the external voltage present on the terminals. It can make the measurement if the
peak voltage is less than 0.4VN or 1000V
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FIXED VOLTAGE
500 V
-- V
Input voltage
Frequency
Input current
Date 2011.05.23
) symbol is displayed alongside it.
maximum. Beyond this value, it does not make the measurement.
AC
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BURN
1000 V
230 V AC
50.0 Hz
24.6 nA
Time 10:31
Megohmmeter Models 6550/6555
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