Subject to change without notice
38
Maximum signal frequency in storage mode
The highest recordable signal frequency cannot be exactly
defined, since it depends to a large extent on the waveform.
With the start of each recording, the signal voltage at the
input(s) of the analog-to-digital converters is briefly measured
(sampled), converted to an 8-bit value and written to an ad-
dress in RAM. The next sampled value is converted in the
same way, but stored at the next RAM address.
The maximum sampling rate is 200MSa/s. This yields a sam-
pling interval of 5ns. Assuming that 10 measurements
(samples) per signal period are sufficient for a sine wave
signal, the maximum frequency to be captured is 20MHz
(50ns per period).
Alias signal display
If, due to the time base setting, the sampling rate is too low,
the display of an alias signal may occur. For example: A sine
wave signal may be sampled only once per period. If the
sine wave signal frequency is accidentally in phase with the
sampling frequency and each sample is taken at the positive
peak value, a straight line is displayed in this position.
Alias signal display may also occur in the form of an apparent
untriggered waveform display of different frequency from
the true signal. Another aliasing condition is the display of
signals seeming to be amplitude modulated.
The easiest way to recognize alias signals is to switch to
analog mode, where the true waveform is displayed. Transfer
from analog to store mode without changing time base range
must produce the same frequency display.
Operating modes of the vertical amplifiers
In principle, the instrument can operate in digital storage mode
with the same operating modes as in analog mode. Thus,
the following can be displayed:
• Channel I by itself
• Channel II by itself
• Channel I and II simultaneously
• The sum or difference of both channels
• XY mode
Storage mode differs from analog operation of the scope in
the following respects:
• In DUAL mode (for simultaneous display of both channels),
both input signals are also simultaneously captured, since
each channel has its own A/D converter. In contrast to
analog mode therefore, it is not necessary to switch bet-
ween chopped and alternating mode.
• Because of the high display rate (approx. 80Hz) of the
screen, no flicker can occur.
• The storage time base is also active in XY storage mode.
Adjustments
As described in the
“Menu”
section, the instrument`s
software contains the submenu
“CALIBRATE”
. The controls
regarding the menus are described under item
MENU (34)
in
section “Controls and Readout”. After a warm up time of 20
minutes, the following items can be used by operators not
equipped with precision instruments.
Both items are regarding the instrument’s temperature
response under extreme environmental conditions. Similar
effects can be caused by component failures as a result of
the application of too high voltage at an input and therefore
cannot
be compensated by the automatic adjustment
procedure. During these automatic adjustments there must
be no signal applied to any input.
1. Y AMP
(amplifier channel I and II field eddect transistors operating
points, invert and variable gain balance)
2. TRIGGER AMP
(trigger amplifier channel I and II DC operating points and
trigger threshold)
3. STORE AMP
(adaptation of the storage display to the analog display)
Attention!
During the automatic adjustment procedure no signal
may be applied to any input.
Information for calling calibration functions is given in
/ MENU
(40) section
Controls and Readout
.
The new adjustment values are always present after the
instrument is switched on.
Note!
The automatic adjustment should only be made if
the instrument’s warm up time has passed and no
faults such as incorrect operating voltages are
present. During the automatic adjustment procedures
the readout indicates “Working”.
RS232 Interface - Remote Control
Safety
Caution:
All terminals of the RS232 interface are galvanically
connected with the oscilloscope and subsequently
with protective (safety) earth potential.
Measurement on a high level reference potential is not
permitted and endangers operator, oscilloscope, interface and
peripheral devices.
In case of disregard of the safety warnings contained in this
manual, HAMEG refuses any liability regarding personal injury
and/or damage of equipment.
Operation
The oscilloscope is supplied with a serial interface for control
purposes. The interface connector (9 pole D- SUB female) is
located on the rear of the instrument. Via this bi-directional
port, the instrument parameter settings and (in storage mode)
signal data, can be transmitted to, or received from a PC.
The maximum connecting cable length must not exceed 3
meters and must contain 9 screened lines connected 1:1.
The pin connection of the RS232 interface (9 pole D-SUB
female) is determined as follows:
Pin
2
Tx data (data from oscilloscope to external device)
3
Rx data (data from external device to oscilloscope)
7
CTS
(clear to send)
8
RTS (request to send)
5
Ground (reference potential - connected via the
oscilloscope’s power cord with protective earth)
9
+5V supply voltage for external devices (max. 400mA)
Adjustments
RS232 Interface - Remote Control
