52
Instrument Functions
nual measurement range selection for high-precision mea-
surements to prevent potential measurement errors due to
incorrect use and other uncertainties. Whenever possible,
make sure to perform measurements with the automatic
measurement range selection activated.
Use the function RNG in the SETUP menu to activate the
manual measurement range selection. Press the knob to
activate the editing mode. You can then press the knob
to select the manual measurement range. If the manual
measurement range selection is activated, you can use the
UP
18
key to manually switch to a higher measurement
range. Press the DOWN
19
key to manually switch to a lo-
wer measurement range.
6.5 Circuit Type
If the automatic circuit type selection is activated (by pres-
sing the AUTO
14
key), the LCR bridge HM8118 will auto-
matically select the circuit type (serial or parallel) that is
best suited for the precise measurement, according to the
connected component. It is also possible to select the cir-
cuit type manually (by pressing the SER
15
key for serial, or
by pressing the PAR
16
key for parallel).
The circuit type displays the equivalent circuit diagram of
the measurement circuit. Typically, the inductance of coils
is measured in serial mode. However, for certain situations
the parallel equivalent circuit diagram may be better suited
to measure physical components. For instance, this is the
case for coils with iron core which most significantly expe
-
rience core losses. If the most significant losses are ohmic
losses or losses in the connecting wires of wired compo-
nents, a serial circuit would be better suited as equivalent
circuit diagram for the measurement circuit. In the auto-
matic mode, the bridge selects the serial equivalent circuit
diagram for impedances below 1kΩ and the parallel equi
-
valent circuit diagram for impedance above 1kΩ.
7 Instrument
Functions
Press the SELECT key to open the main menu. The main
menu enables you to access the submenus SETUP, CORR
and SYST via numeric keypad.
7.1 SETUP Menu
7.1.1 Measurement Frequency FRQ
The LCR bridge HM8118 includes a measurement fre-
quency range from 20 Hz to 200 kHz (in 69 increments)
with a base accuracy of 100 ppm. The 69 increments of the
measurement frequency range are as follows:
Measurement Frequencies
20Hz
90Hz
500Hz
2.5kHz
12kHz
72kHz
24Hz
100Hz
600Hz
3.0kHz
15kHz
75kHz
25Hz
120Hz
720Hz
3.6kHz
18kHz
80kHz
30Hz
150Hz
750Hz
4.0kHz
20kHz
90kHz
36Hz
180Hz
800Hz
4.5kHz
24kHz
100kHz
40Hz
200Hz
900Hz
5.0kHz
25kHz
120kHz
45Hz
240Hz
1.0kHz
6.0kHz
30kHz
150kHz
50Hz
250Hz
1.2kHz
7.2kHz
36kHz
180kHz
60Hz
300Hz
1.5kHz
7.5kHz
40kHz
200kHz
72Hz
360Hz
1.8kHz
8.0kHz
45kHz
75Hz
400Hz
2.0kHz
9.0kHz
50kHz
80Hz
450Hz
2.4kHz
10kHz
60kHz
You can set the measurement frequency either in the SE-
TUP menu via FRQ or via FREQ
8
key by means of the
knob
6
or the
keys
7
. If the automatic measu-
rement range selection is activated (AUTO
17
) and the im-
pedance exceeds a value of 1000 Ω, a change in the mea
-
surement frequency may result in a change in circuit type
(serial or parallel). In case of high impedances and a power
frequency of 50 Hz/60 Hz, a measurement frequency of
100 Hz/120 Hz may result in an instable measurement va-
lue display due to interferences with the power frequency.
Therefore, depending on the power frequency, it will be
necessary to select a different measurement frequency.
7.1.2 Voltage LEV
Fig. 7.1: Menu function SETUP display