Measuring Range; Auto-Ranging; Manual Range - Hameg HM8018 Benutzerhandbuch

O p e r a t i o n o f t h e H M 8 0 1 8
resistance, thus the voltage at the component
terminals will be always below 0.5 V. The source
resistance is as a function of the impedance ran-
ge. The graph shows the voltage evolution at the
component terminals as function of its impedance
and the measuring range (R1 range 15 Ω, R6 range
100 MΩ).

Measuring range

The HM8018 offers 6 impedance ranges (R1-R6).
The measuring range can be selected either
manually or automatically. Each range has a
source resistance approximately equal to half of
the impedance of the current range. The extreme
ranges R1 and R6 use the source resistances of
the R2 and R5 ranges.
Note: The measuring ranges determine the impe-
dance ranges (and not capacitance or inductance
value ranges), the ranges of capacitance and
inductance depend upon the test frequency. The
high capacitance values as the low inductance
values will be measured on a low impedance
range, whereas the low capacitance values as
the high inductance values will be measured on
the higher ranges.
The chart below gives the measurement range
according to the component type and the fre-
quency range.
Range
source
R1 100 Ω
R2 100 Ω
R3 1 kΩ
R4 10 kΩ
R5 100 kΩ
R6 100 kΩ 330 kΩ –
f is the test frequency (Hz)

Auto-ranging

In normal operation the HM8018 selects the most
appropriate range for an accurate measurement.
When the instrument measures impedance that it
is out of its current range, the instrument switches
one range up or one range down and makes a new
22
Subject to change without notice
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R Resi- Induc-
stance tance (H)
1mΩ – 0.01 µH –
15Ω 2.4/f
15Ω – 2.4/f –
330Ω 52.5/f
330Ω – 52.5/f –
3.3 kΩ 525/f
3.3 kΩ – 525/f –
33 kΩ 5252/f
33 kΩ – 5252/f –
330 kΩ 52520/f
52520/f
100 MΩ 9999
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measurement. If this measurement is within the
validity domain of this new range the instrument
will display the value. If not, the range change
process will be repeated. There is a built in hy-
steresis in the order of 10% to prevent multiple
range changes if a component is on the limit of
range boundary. The chart below gives the limits
of range changes.
Range
Change
1 to 2
2 to 3
3 to 4
4 to 5
5 to 6
Remarks:
If certain types of inductors are measured it may
occur that the HM8018 switches indefinitely bet-
ween two ranges. Due to the fact that generally
the inductor value depends of the current going
through, the HM8018 will give different values
from one range to an other because the source
resistance changes. This variation from one range
to another may be higher than the automatic mode
hysteresis that creates irresolution. So it is ne-
cessary to switch to manual mode to fix the range

Manual range

When an important quantity of similar components
has to be tested, the automatic mode process
Capaci-
duration time can be avoided. While a component
tance
99.9 mF – is measured in automatic mode, press the AUTo
10.6/f mF
button. The current range (selected by the instru-
10.6/f mF –
ment) is hold and displayed for a short time. It is
482/f μF
possible to save the configuration settings for a
482/f μF –
further use by pressing the SToRE button and
48.2/f µF
then CONFIG key. If the impedance of the com-
48.2/f µF –
ponent is higher than 50 times the nominal value
4.82/f µF
for the range (given by R source resistance), the
4.82/f µF –
message OFL is displayed. Then you must change
0.48/f µF
0.48/f µF – the range. This not applies to the 15 Ω range for
0.001 pF
which overtaking is obtained for an impedance of
approx. 18 Ω. As far the higher range R6 allows
measurements up to 99.9 MΩ.
The manual range mode, thus, is to be reserved to
precise cases. To avoid measurement instability
and additional uncertainty the instrument should
be ever working in automatic range mode.
Range
|Z|
Change
|Z| > 15 Ω 2 to 1 |Z| < 13.5 Ω
|Z| > 330 Ω 3 to 2 |Z| < 300 Ω
4 to 3
|Z| > 3.3 kΩ
5 to 4
|Z| > 33 kΩ |Z| < 30 kΩ
|Z| > 330 kΩ 6 to 5 |Z| < 300 kΩ
|Z|
|Z| < 3 kΩ