33
Subject to change without notice
F i r s t - t i m e o p e r a t i o n
affect the settings stored
in memories 0 to 8. After
turn-on the settings in me-
mory 0 will be automatically
loaded. Pressing the RE-
CALL/STORE button
41
will
alternate between recalling
and storing of settings.
Display of main and second measurement results
The LCR bridge HM8118 is able to measure and display two
parameters simultaneously selected from 9 measurement
functions. The fi rst parameter is related to the „fi rst or main
measurement value display“, and the second parameter to the
„second measurement value display“. Depending on the com-
ponent connected the pairs may consist of: L and Q, L and R, C
and D, R and Q, Z and
Θ
, or Y and
Θ
, and additionally N and
Θ
or M (with transformers). The measurement functions can be
selected by pressing the buttons
29
to
39
.
The actuall measured „ohmic“ resistance includes any re-
sistance of wires and the foils in capacitors (if those are
connected in series) as well as the ESR (equivalent series
resistance) caused by dielectric losses (D). ESR and D are
represented by the following formula:
ESR = R
series
= D/
ω
Cs (
ω
= 2
π
f)
Traditionally, the inductance of coils is measured in a series
circuit; however there are cases where a parallel circuit will
yield a better representation of the component. In small „air“
coils mostly the ohmic or copper losses are predominant , hence
the series circuit is the proper representation. In coils with an
iron or ferrite core the core may contribute most of the losses,
here the parallel circuit is in order. .
Display of measurement results
Three different representations of measurement results are
available on the LCD display:
MEASUREMENT VALUE, relative
DEVIATION Delta ABS or relative DEVIATION
Δ
% in percent).
Press the SELECT button
3
and select the menu SETUP,
choose DEV_M for the display of the “Main Measurement Va-
lue“ and DEV_S for the „Second Measurement Value“. The LCD
display will show the main and second measurement values,
decimal point and units. The resolution of the main value display
(L,C,R,G,Z,Y) is 1 to 3 digits preceding and 3 to 5 digits following
the decimal point.
The resolution of the second value (D, Q, R, B, X,
Θ
) is 1 to 3
digits preceding and 3 to 5 digits following the decimal point.
If any value is beyond the measurement range selected OVER-
RANGE will be displayed. After a range was selected a change
to a lower or higher range is possible.
Δ
% (#, %)
The „#“ sign preceding a value and the „%“ sign following it
designate a display of the „relative deviation
Δ
%“ in percent
of the measured value of L,C,R,G,Z,Y or D,Q,R,B,X;
Θ
with
respect to a stored nominal value.
Δ
ABS (#)
The „#“ sign preceding a value designates the display of the
absolute deviation of a measured value with respect to a
stored nominal value, similar to
Δ
%, but here the deviation
is displayed with the appropriate unit (Ohms, Henries etc.).
Nominal value (REF_M, REF_S)
This function allows you to store “nominal values“ for the
two measurement values which serve as the references when
any of the functions „
Δ
%“ or „
Δ
ABS“ is selected. In order to
store a reference value, press the SELECT button
3
, use the
SETUP menu and choose REF_M for the main value reference
resp. REF_S for the second value reference. The proper units
are automatically chosen according to the measurement
functions selected for the main (H,F,
Ω
, S) and second (
Ω
,
S, degrees) measurement values. A nominal value may be
entered with up to 5 digits following the decimal point
Measuring range
The HM8118 allows manual and automatic range selection. In
some cases it is advisable to choose manual operation, because
autoranging always requires a full cycle until the proper range is
found. Manual range selection is especially helpful when similar
components are to be inserted and removed into/from a test
fi xture. HM8118 will automatically switch to the highest range,
any time a component is inserted it will switch to the appropri-
ate range and back to the highest range when the component
is removed. If the auto mode is disabled and the impedance of
the component is beyond 100 times the full range selected the
bridge will display OVERRANGE, in such case another range
should be chosen.
STOP
Please note:
If a component is measured in a non-optimum
range, the accuracy of the measurement will be
impaired
The deterioration of the accuracy outside the optimum range
is calculated as follows:
The best accuracy is achieved if the measuring value of the DUT
(device under test) is close to full range. If the next higher range
is selected, this value will appear in its center. As the measuring
error is given in percent of full range the permissible error in
this new range will be appr. twice that in the former, proper
range. Of course, in any still higher range the permissible error
will increase accordingly.
If similar components are to be measured it is advisable to hold
the appropriate range and function by pressing AUTO/HOLD/
RANGE
17
in order to prevent continuous auto switching when
components are removed or inserted from resp. into the test
fi xtures or connected/disconnected to/from cables.
Measurement speed
The LCR bridge HM8118 allows you to select any of 3 measure-
ment speeds: SLOW, MED, and FAST. The maximum speeds are:
1.5 meas. per second in SLOW, 8 in MED, and 14 in FAST. The
speed selection infl uences the achievable accuracy: the slower
the better. At very low measuring frequencies the speed is au-
tomatically reduced. For speed selection press SELECT, access
the menu SETUP, choose SPD (for speed) and use the knob.
Trigger source/ Trigger mode
The HM 8118 features several trigger modes and sources. The
available trigger modes are: CONT (continuous), MAN (manual),
and EXT (external).
CONT:
at the end of each measurement a new measurement
will be automatically triggered.
