45
Introduction
3 Introduction
3.1 Requirements
❙ R&S®HM8118 LCR measuring bridge with firmware from
1.37 upwards.
❙
R&S®HZ184 Kelvin measurement cables
❙
1 x 1,000 µF capacitor (not contained in shipment)
❙
1 x 280 µH inductor (not contained in shipment)
❙ 1 x 100 kΩ resistor (not contained in shipment).
First connect the R&S®HZ184 cables supplied to the
R&S®HM8118. The two plugs of the black cable are con-
nected to the terminals LCUR and LPOT, the plugs of the
red cable to the terminals HCUR and HPOT.
After turning the instrument on, the first steps are the
open circuit and the short circuit calibration procedures at
the preselected frequency of 1.0 kHz because the measu-
rement cables R&S®HZ184, in conjunction with the termi-
nals, due to their design, show a stray capacity, a residual
inductance and a residual resistance which impair the ac-
curacy of the measurement results. In order to minimize
these influences, the compensation of impedance measu
-
rement errors caused by adapters and cables is necessary.
For the open circuit calibration, position the two clips apart
from each other. For the short circuit calibration connect
both clips as shown in Fig. 3.1.
Push the button MENU/SELECT
3
and then the button
C-D
34
in order to enter the CORR menu. Select the menu
item MODE and use the knob
6
to change the menu entry
from SGL to ALL in order to automatically perform the cali-
bration at all 69 frequency steps provided. Leave the menu
by pushing the button MENU/ESC
5
.
The following components are only intended to be used as an ex-
ample for a quick introduction to the instrument.
Fig. 3.1: Short circuit calibration with R&S®HZ184.
The mode SGL is used to only calibrate at the presently selected
frequency; this procedure takes just a few seconds and is desti-
ned for measurements in one or a few frequency ranges only.
Now start the open and short circuit calibrations by
pushing the buttons ZERO/OPEN
11
resp. ZERO/SHORT
12
. The instrument will now determine correction factors
at all 69 frequency steps valid for the presently connected
measurement cables and store them until the instrument is
switched off. This procedure will last appr. 2 minutes.
3.2 Measurement of a capacitor
Now connect the capacitor to the terminals of the
R&S®HZ184. Please observe the polarity of the capacitor
and connect the black terminal to the negative terminal of
the capacitor, marked with a – (minus).
As the instrument is set to automatic mode, the measure-
ment function will be automatically switched to function
no. 3 (C-D). Because the measuring frequency of 1.0 kHz
was preselected, the capacitor will not be measured in its
regular operating mode, so the value displayed of appr.
900 µF will not equal the specified value of 1,000 µF.
Change the measuring frequency to 50 Hz by pushing the
button SET/FREQ
8
and turning the knob until 50 Hz are
shown on the display. Now the value displayed will change
to appr.1,000 µF depending on its tolerance. The dissipa-
tion factor „D“ will be very low at this setting.
The smaller the loss angle, the more the real world com-
ponents will come close to the ideal. An ideal inductor has
a loss angle of zero degrees. An ideal capacitor also has
a loss angle of zero degrees. An ideal electrical resistor,
however, has a loss angle of 90 degrees, it has no capaci-
tive or inductive components.
3.3 Measurement of an inductor
Before you connect the choke, increase the measuring fre-
quency by one decade to 500 Hz by pushing the arrow
button
7
above the knob. Disconnect the capacitor and
connect the choke to the terminals of the HZ184.
The instrument will now automatically switch to the func-
tion no. 1 (L-Q) and the inductance of the choke will be dis-
applied on the red terminal.
The bias voltage works only
when the instrument on capacitance measurement
mode.
Measuring function selection
The desired test function is selected by push buttons (12)
and (14). The push button (12) gives access to the main
parameter (R, L or C), The push button (14) allows a
secondary parameter measurement (Q/D, impedance or
phase).
In order to measure D parameter the instrument needs at
first to be set to capacitance measurement mode, on the
other way, Q parameter will be displayed.
Auto-measurement function
The HM8018-2 is able to automatically determine the
component type in most cases. 3 different automatisms
exists: the automatic impedance range selection (see the
section «
Auto-ranging»), the automatic mode
(series/parallel) selection (see the section «
passive
components »), and the automatic function selection. These
three automatisms are simultaneously activated when the
instrument is set in automatic mode with the
RANGE
AUTO
key (7). Then the user can change function or mode
that disables their respective automatism. The manual range
selection disables the three automatisms.
When the instrument is on automatic mode the function
choice depends on the impedance module, phase angle as
well as the quality factor .The diagram below shows the
choice made by the instrument.
|Z| = 1000
Ω
Q = 500
D = 0,002
Q = 500
D = 0,002
D = 500
Q = 0,002
D = Q = 1
D = Q = 1
R
jX
D = 500
Q = 0,002
Calculation functions
Apart from displaying normal values as resistance, inductance or
capacitance, the HM8018-2 can display relative deviations and
percentages. It is not possible to use these calculation modes for
other functions than the three previous values. The deviations
and percentages are displayed in relation to the two stored values
A and B.
The procedure to obtain relative measurement is as follows:
1)
Connect the component corresponding to the reference
value.
2)
Store the value (memory A) by pressing on the
STORE
key,
then press the
A
key.
3) Press on the
A
key. The indicator
-A
lights up and the
display shows the value (
Measure
– A).
A direct percentage measurement is possible, it is only to use the
÷
B
key instead of the
–A
key in the previous procedure. Then the
instrument displays the value 100*
Measure
/B in %.
To obtain a deviation in % proceed as follows:
1)
Connect the component corresponding to the reference
value.
Fig. 3.2: R&S®HM8118 measurement principle, left: schematic, right:
detailled presentation.
Imaginary
Axis
below -- 45° = C
above 45° = L
Real
Axis
ph
ase
an
gle
Summary of Contents for HM8118
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