Displaying Curves - Hameg HM 6042 Handbuch

U s i n g o f t h e H M 6 0 4 2
The base current at the indicated cursor position is displayed
on the LCD with I selected by the push buttons
B
When FETs are under test the rotary knob
the gate voltage V between –10 V to +10 V in 256 incremental
G
steps. This means 80 mV / step approximately.
Five curves (I = f (V ), I = f (V
C CE D
screen to represent the characteristic behavior of a transistor
under test. After selecting the MIN or MAX
push button FUNCTION , the rotary knob
modify the minimum/maximum base current/gate voltage in a
sense so that the five curves fit for the operating range to be
evaluated. Care has to be taken not to supersede the safe
operating area of the device. Use the P
limit the power applied to the device.
Please consider not exceeding the current and
voltage settings beyond the DUTs power
dissipation limits otherwise it might be destroyed.

Displaying curves

STOP
Figure 1
The I and V settings determine the operating range for
max max
the test and define how the curves are going to be displaying
on the CRT screen. As shown in Figure 1, the upper edge of
the grid represents the maximum value of the test current (I
I ) according to the selected range (I
D
Figure 2
22
Subject to change without notice
I .
B
allows adjusting
)) normally are displayed on the
G
setting with the
can be used to
22
setup to automatically
max
= 200 mA / 20 mA / 2
max
mA). The right edge of the 8 x 10 screen grid represents the
maximum value of the selected voltage range (V
2 V). The display is linear along both axes. For example, if V
set to 40 V and I is set to 20 mA the horizontal resolution will
max
be 4 V / DIV. and the vertical resolution will be 2.5 mA / DIV. This
applies in an analogous manner if smaller ranges are chosen.
The maximum power is selected with buttons P
characteristic diagram is a hyperbola which trims the maximum
values of current and voltage. If the limit values of the DUT are
smaller than the testable limits of HM6042, the run of the
hyperbola is visible (Figure 2).
Significant for the distances between the curves of the set of
characteristic curves I
current and thus the distances between the curves can be
changed using the MIN or MAX function
the rotary knob . With the function MAX activated, the hori-
zontal position of the top curve is modified by changing the
base current. If the function MIN is selected the position of
the bottom curve is set. The three characteristics between
these two will be displayed in equal distances.
Figure 3
After power on the base current is preset to minimum value.
(Figure 3). After activating function MAX or MIN the position
of the curves can be adjusted within 3 ranges. Thereby an ad-
, ditional offset has to be considered in every range. The offset
C
amounts a half step. Continuous passing through the ranges
from the lowest to the highest is possible if the rotary knob
is turned clockwise. A skip from step 127 to step 128 involves
a change of range. The first 5 steps of the new range are equal
to the last 5 steps of the last range. When changing the ranges
the base current is multiplied by 10. It has to be considered
that range 3 (10 mA base current) cannot be reached if the the
collector current is limited to 2 mA by keys I
Continuous passing through the ranges from the highest to
the lowest is possible if the rotary knob
counterclockwise. With function MIN activated and turning the
rotary knob clockwise the bottom curve will be moved from
the bottom up (see Figure 4).
As soon as the HM6042 is switched on, a baseline is visible at
the CTR screen as long as no DUT is inserted. If a bipolar
transistor is connected and the measurement is started by
14
pressing DUT a more or less diversified set of charac-
teristics is displayed. Figure 3 shows how a typical display
may look with these basic settings selected. If e.g. a NPN
= 40 V / 10 V /
max
max.
= f(U ) is the parameter I
C CE B
and then turning
max 19
.
is
max
23
. The
. The base
is turned