Hameg Instruments HM 8042 Bedienungsanleitung Seite 14

— The actual gate voltage can be read on the HM 8042
display when V,/V, Is selected using the Test
Parameter Switch [6].
Caution! When measuring FET's itis possible that
voltages up to 50Vp- are present on the compo-
nent. This is the case when V,>=40V and V,=-10V
are selected. Anyone using this equipment needs
to be advised of the possible danger and the
proper precautions to take when working with
voltages of this level.
Selection of Parameters
Generally, Transistor parameters are separated into
two categories, Static and Dynamic. The parameter
to be displayed is selected using the Test Parameter
Switches [6] and [8]. The value of the selected para-
meter will be measured at the position of the
Cursor(explained below) and shown on the HM 8042's
digital display.
Static Parameters
Vip/V, Base/Gate Voltage
le/le Base/Gate Current
L/lp Collector/Drain Current
Voi/Vp Collector/Drain Voltage
B Current Gain
Dynamic Parameters
are Short-circuit Input impedance
apy Short-circuit forward-current transfer ratio
A> Open-circuit output conductance
Var Short-circuit forward admittance
Yo. Short-circuit output admittance???
Use of the Cursor
When the HM 8042 is put into use, acursor is present
on the middie curve of the 5 characteristic curves.
The cursor is repositioned using the Cursor Vertical
Position Switch[18] and the Cursor Control Knob.
Press the Cursor Vertical Position Switch to move the
Cursor from one curve to the next. Select <> andturn
the Cursor Contro! Knob to move the cursor along the
curve. The cursor moves 1/8 division per step
horizontally giving 64 possible positions along the
curve. The selected static parameter for the cursor
position will be displayed on the HM 8042 Digital
Display.
When dynamic parameters hy, hz, ory>, are selected,
a second cursor appears on the curve below the
M6 ~ 8042
original cursor. Turning the Cursor Control Knob moves
both cursors along their respective curves. The HM
8042 measures both values and displays the calculated
result on the digital display.
When dynamic parameters h., or y, are selected, a
second cursor appears on the same curve as the
original cursor. Selecting <> and turning the Cursor
Control Knob will change the position of the second
cursor in relation to the first. Selecting TRK and
turning the Cursor Control Knob will move both
cursors along the curve simultaneously. The HM
8042 measures both values and displays the calculated
result on the digital display.
Use of the Memory Function (MEM)
To aid in the selection of transistors, the HM 8042
provides a very heloful Memory Function. Pressing
the MEM Switch [9] stores the parameters of the
transistor and allows them to be compared with the
parameters of a second transistor of the same type.
Thus selection of a transistor for specific parameters
(le/lp, B, Ais, Nor, Ae, Yor, ANG 29) IS easily accomplished
as follows:
1. Measure the desired parameter on the Reference
transistor.
2. Press the MEM switch. The static parameters of
the reference transistor will be stored, a Acharacter
appears in the digital display, and - 0 - is displayed
as the value.
3. Press the DUT switch, remove the reference
transistor, and insert the transistor to be tested.
4. Press the DUT switch. The digital display will
show the difference in the values of the 2 transistors
for the selected parameter.
5. Press MEM again to return the test set to normal
operation.
Storage of the Curves
It is possible to store the curve display when using a
HM 408 or HM 1007 Digital Oscilloscope. The stored
display can then be printed using the HD 148 graphic
printer or sent to other equipment using the HO79-4
Multifunction-Bus. Even though some curve data
will be lost due to the resolution limitations(8 bit
vertically) of the digital oscilloscope, a relatively good
representation is possible. The curves displayed in
this manual were prepared using the HM1007, HM79-
4 anda PC using SP 91 software.
Subject to change without notice