Hameg HM 203, Руководство пользователя

Страница: 3 / 43

Technical Details
General
The high performance and competitive price of the
HM203-4 has been achieved by the optimum use of
both discrete semiconductor and
integrated circuit
technology. Quality and long term reliability are assured,
as only
high quality components are selected for the
instrument. The well-arranged subassemblies combined
with a stable construction ensure easy servicing. The
subdivision of the complete circuitry into two large
printed circuit boards enables each component to be
easily reached, without dismantling any other parts.
A square-wave generator for probe compensation and a
trace rotation device are incorporated.
Each instrument is supplied with a comprehensive
manual including operating and servicing instructions,
circuit diagrams, and PCB layouts. It also contains test
instructions for checking the most important functions
by relatively simple means.
Modes of Operation
The HM203 can be used for single or dual trace opera­
tion. Two time-related signals differing in waveform and
amplitude can be displayed either consecutively
(alter­
nate mode) or by the multiple switching of the channels
within one sweep period (chop mode). The sum or the
difference of two signals are displayed by algebraic addi­
tion (Channel I can be inverted). When X-Y operation is
selected, the X input is via Channel II. Input impedance
and sensitivity ranges are then the same for both X and Y
deflection.
Vertical Deflection
The HM203 has two preamplifiers with diode-protected
FET inputs. These are electronically switched either
individually, alternately or together to the Y final
amplifier. The switching circuit operates with bistable-
controlled diode gates. Control for the alternate mode is
effected by the unblanking pulse from the sweep
generator and for the chopped mode by a 1 MHz signal.
The chop generator and the bistable multivibrator are
both combined in a single integrated circuit. The
preamplifier input stages utilize
monolithic integrated
circuits to minimize drift. Exact measurement of the
displayed waveform is achieved by the 1 2-step frequen­
cy compensated input attenuator calibrated in V/cm. In
order to obtain reliable triggering at higher frequencies,
the bandwidths of the preamplifiers are approximately
40MHz. The total bandwidth of the Y amplifier is
dependent on the output stage. The value stated refers to
-3dES (70% of 80mm).
Timebase and Triggering
The timebase of the HM 203 operates with a new type of
trigger technique developed by HAMEG. Here, the entire
trigger preparation is through a monolithic integrated
volage comparator whose TTL output is connected
directly to the control logic of the sweep generator. The
fast operation of this circuit means that
very small signal
amplitudes up to a frequency of 4 0 MHz can be reliably
triggered. Using AC, DC, HF- or LF-filter coupling,
automatic or normal triggering from positive- or negative­
going trigger edges can be selected from Channel I,
Channel II, Line or external sources. With the trigger
switch in the
Auto position, a baseline is always
displayed even in the absence of a signal. The HM203
allows the triggering of
TV signals (line or frame frequen­
cy). A voltage-proof opto-coupler controls the unblank­
ing of the CRT.
Component Tester
By simply pressing a single pushbutton, the HM203
can be switched into test mode without actually affect­
ing the oscilloscope measuring set-up. The test result is
displayed on the screen in the way of a typical current-
voltage characteristic. Display height and width are con­
stant. Test voltage and current are such that standard
semiconductors and other components cannot be
damaged.
Components can be tested individually or
"in-circuit” . Easy and time-saving troubleshooting is
possible in complex circuitry by simple comparison with
an equivalent functioning circuit. Simply release the
Component Tester pushbutton to resume normal
oscilloscope measurements.
Examples of test displays
Short-circuit
Z-diode below 8 volts Transistor base-collector Transistor base-emitter
paralleled to I^ F + 6 8 0 0
P2 2/83