Hameg HM8118 User Manual Download Page 26

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Measuring Equipment

The measurement adapter HZ186 is designed for measure-
ments of transformers or transmitters in combination with
transformer measurement functions of the LCR bridge
HM8118. The measurement adapter is directly connected
to the front panel BNC connectors of the LCR bridge via
the four BNC sockets.

The 4-wire transformer test lead is a convenient tool to
measure the mutual inductance (M), the transformer ra-
tio (N) and the phase difference

in a frequency range

between 20Hz and 200kHz of a transformer or transmit-
ter. The measurement adapter serves as interface between
the LCR bridge and the four included test leads. For the
measurement, the transformer / transmitter to be measu-
red is connected to the measurement adapter via test lead,
according to the imprinted wiring on the primary and the
secondary side. This equipment is optional and is not in-
cluded in delivery.

8.3.1 Compensation HZ186

Due to their design, the test lead HZ186 and the connected
test leads have a fringing capacitance, self inductance and
self-resistance which impacts the accuracy of the measu-

1 Transformer test adapter
2 Test lead for high number of windings
3 Test lead for low number of windings

Fig. 8.7: 4-wire transformer test lead

In case of a faulty measurement, the LCR bridge does not display
any value for N.

red values. To minimize these impacts, the compensation
of impedance errors caused by adapters and leads beco-
mes necessary.

To compensate or eliminate this measurement error, it is
recommended to perform an open and short compensa-
tion (OPEN/SHORT compensation) with the LCR bridge
HM8118. For the open compensation, the four test leads
are connected to the measurement adapter HZ186. Be-
fore starting the open compensation, the two black test
leads (which are connected to the „COMMON“ BNC con-
nectors) are connected. It is also necessary to connect the
two red test leads that are connected to the BNC connec-
tors „N“ and „1“.

For the short compensation, the two red test leads and the
two black test leads are connected to each other.

8.3.2 Transformer Measurement

The measurement of a transformer can always result in va-
rying measurement results. This is related both to the iron
core losses as well as to the unknown state of the prema-
gnetized core. The component to be measured is depen-
dent on the frequency as well as on the applied measure-
ment voltage. The measuring instrument determines the
values for L, R and C by measuring the impedance and the
related phase angle. The angle determines an inductive,
capacitive or real value (L,C,R). Consequently, the amount
of the impedance increases as the voltage increases, and
the phase angle is heavily dependent on the measurement
frequency (due to change in magnetization and iron core
loss and visible in the „Z-Theta“ mode [7]). If a transformer
is measured as „open“, the measurement values are plau-
sible. However, if the secondary side is short-circuited, it is
only possible to measure considerably fewer measurement
values. The values in case of a short-circuited secondary
page correspond nearly precisely to the core losses.

8.3.3 Mutual Inductance

To measure the mutual inductance, the HM8118 applies
the same procedure as for the regular inductance. Instead
of measuring the voltage via primary winding, the voltage
will be measured at the secondary transformer winding.

For frequency dependent components, make sure to perform
an OPEN and SHORT compensation for each of the 69 test
frequencies.

Änderungen vorbehalten

Für den „Kurzschlussabgleich“ sind die beiden roten Mess-

leitungen und die beiden schwarzen Messleitungen gemein-

sam miteinander zu verbinden.

Bild 2: OPEN-Abgleich = trennen

SHORT-Abgleich = kurzschließen

Bild 3 „Primär- und Sekundär Transformator“

Bild 4 „Spar-Transformator“

HAMEG HZ186

COMMON

trennen