Hameg Instruments HM 8042 Bedienungsanleitung Seite 12

Safety advice
Due to its measuring technique, voltages up to 50V
are present at the 4mm banana connectors marked
E/S, C/D and B/G. Therefore, it is assumed that the
HM 8042 will only be operated by qualified personnel
which are acquainted with the danger involved.
General
The HM 8042 provides DC parameter characterization
of 2-and 3-pole semiconductor devices like transistors,
diodes, MOSFETs. The characteristic curves are
digitized and displayed on an oscilloscope working in
the X/Y-mode. By means of cursors which can be
precisely positioned on screen, accurate measure-
ments of the parameters can be performed. The
microprocessor operated instrument is extremely
versatile, yet remarkably easy to operate. Most of the
instrument set-ups are made automatically according
to the selected measuring function.
Operation
For the operation of the HM 8042 no special expertise
is required. The instrument is easy to set-up and
operation is straight forward. Nevertheless, a few
basic guidelines should be followed in order to ensure
problem-free operation of the curve tracer with the
oscilloscope.
A special cable for connecting the HM 8042 to the
oscilloscope is supplied as a standard accessory. It is
shielded and has BNC-connectors on one end and
two special connectors on the other end. It is
connected to the special jacks (3) of the HM 8042 and
the BNC-inputs of the oscilloscope. Exchanging the
two cables for one another does not cause any
damage to the instruments, but it has the effect of
rotating the displayed image of the signals by 90
degrees on the cathode ray tubes. If this happens,
merely swap the cables.
Power is supplied to the HM 8042 via the HM 8001
or the HM 8001-2 mainframes. When using the HM
8001-2 with option HO801 (4 BNC connectors at the
rear) installed, the connection of the HM 8042 to the
oscilloscope can be done via the rear outputs of the
HM 8001-2 by means of standard BNC-cables.
Basic settings
In order to run the set-up correctly, some basic
settings are required. The oscilloscope is operated
in X/¥-mode. Both channels must be set to a
sensitivity of 0.5 V/div.. When doing so, make sure
that the adjustment knobs for variable sensitivity
are in the calibrated position. The input coupling
switches are then set to DC position and the position
of the beam is adjusted so that it starts on the
baseline one division apart from the Jeft screen
limit. As soon as the HM 8042 is switched on, a
baseline with a length of 8 divisions is visible (as
long as no DUT is connected). A bright spot on the
baseline indicates the cursor position. The device
adapter which ts supplied with the HM 8042 is
connected to the banana sockets (4).
M4 - 8042
Connecting components to the HM 8042
Besides the standard device adapter Hameg offers
different adapters sockets for component connection
to the HM 8042. The standard device adapter supplied
with the HM 8042 can be used to alternate compare
two DUTs.
The banana sockets (4} on the HM 8042 are designated
as E/S Emitter/Source, C/D Collector/Drain and B/G
Base/Gate. The DUT can be directly connected to the
terminals by means of single cables with a max.
length of 25cm each. The display of the characteristics
can be degraded due to hum and noise on the cables.
Shielded cables cannot be used due the stray
capacitance. Diodes are measured between the
terminals E and C.
When using single cables extreme care has to be
taken tor safety purposes.
Selection of the DUT-type
The HM 8042 must be set-up according to the type of
the DUT. In case of a NPN-bipolar Transistor the
switches (12) and (15) must be released. For PNP-
Transistors the button (15) must be depressed
accordingly. Selection of FETs is done by means of
button (12) also. Diodes are measured with the same
set-up as FETs. To start a measurement the button
DUT (2} must be depressed. It is a toggle switch and
activates/deactivates the measurement. In case the
device is not active, the 4digit display shows -off-.
Setting of the measurement ranges
When the active DUT is a transistor a set of 5
characteristic curves lc=f(Uce) is displayed on the
screen. Incase only one curve Is visible with the basic
setting, the upper currentlimit can be changed via the
rotary dial when the function MAX [20] is selected.
Thus 5 characteristic curves can be displayed. Care
must be taken, that the current and voltage settings
does not pass the DUT limits. The HM 8042 limits
voltage and current only to the selected max. setting
of the range.
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Figure 1
Subject to change without notice