23
Subject to change without notice
1.2.1.4
TRIG SYMBOL ON/OFF
In most of the Yt (time base) modes the readout displays a trigger
point symbol which will not be displayed in condition OFF.
1.2.1.5
DC REF ON/OFF
If
ON
is selected and
Yt
(time base) mode is present, the
readout displays a ground symbol (
⊥
⊥⊥
⊥⊥
). This symbol eases the
evaluation and determination of DC contents by indicating the
0 Volt reference position.
1.2.2
FACTORY
contains
1.2.2.1
LOAD S/R DEFAULT (S/R = SAVE/RECALL)
.
This overwrites all
SAVE/RECALL
memories with the following
instrument setting: Single channel operation (
“Y1:500mV~”
),
time base (“T:100µs”), automatic peak value triggering and
AC trigger coupling.
1.2.2.2
RESTORE FACTORY DEFAULT
If inadvertently an adjustment was performed in
CALIBRATE
MENU
condition, which was not stored by
OVERWRITE
FACTORY DEFAULT
, the factory adjustments can be recalled
by this function.
1.2.2.3
OVERWRITE FACTORY DEFAULT
Attention!
Calling this function causes the factory adjustments to
be overwritten by new data. The factory adjustment
then is lost and can not be recalled by RESTORE
FACTORY DEFAULT.
This function is only intended for those cases in which
an adjustment can be performed with very expensive
”0% error” calibrators, to adjust the instrument for
optimum tolerance when operated under extreme en-
vironmental conditions.
1.3
HO79
This information will only be displayed if the interface
HO79-
6
is connected to the oscilloscope.
For further information
please note the HO79-6 manual which is supplied with the
interface.
First Time Operation
The following text assumes that the
“SAFETY”
section of this
manual has been read carefully and understood.
Each time before the instrument is put into operation check that
the oscilloscope is connected to protective earth. For that reason
the power cable must be connected to the oscilloscope and the
power outlet. Then the test lead(s) must be connected to the
oscilloscope input(s). Check that the device under test is switched
off and connect the test lead(s) to the test point(s). Then switch
on the instrument and afterwards the device under test.
The oscilloscope is switched on by depressing the red
POWER
pushbutton. After a few seconds the
HAMEG
logo and the
instrument software release is displayed on the screen. As
long as the
HAMEG
logo is visible different internal checks are
made. Thereafter the instrument will revert to its last used
operating mode.
If after approx. 20 seconds no trace is visible, the
AUTO SET
pushbutton should be pressed briefly. This selects the Yt
mode and medium trace and readout intensity (please note
“AUTO SET”
). Adjust
Y-POS.I
and
X-POS.
controls to center
the baseline. Adjust
INTENS.
(intensity) and
FOCUS
controls
for medium brightness and optimum sharpness (input(s)
grounded) of the trace. The oscilloscope is now ready for use.
If the
AUTO SET
function was not used and only a spot
appears (CAUTION! CRT phosphor can be damaged), reduce
the intensity immediately and check that the XY mode is not
selected (XY not displayed in the readout).
To obtain the maximum life from the cathode-ray tube, the
minimum intensity setting necessary for the measurement in
hand and the ambient light conditions should be used.
Particular care is required when a single spot is displayed, as
a very high intensity setting may cause damage to the
fluorescent screen of the CRT. Switching the oscilloscope off
and on at short intervals stresses the cathode of the CRT and
should therefore be avoided.
The instrument is so designed that even incorrect operation
will not cause serious damage.
Trace Rotation TR
In spite of Mumetal-shielding of the CRT, effects of the earth’s
magnetic field on the horizontal trace position cannot be
completely avoided. This is dependent upon the orientation of
the oscilloscope on the place of work. A centered trace may
not align exactly with the horizontal center line of the graticule.
A few degrees of misalignment can be corrected by a
potentiometer accessible through an opening on the front
panel marked TR.
Probe compensation and use
To display an undistorted waveform on an oscilloscope, the
probe must be matched to the individual input impedance of
the vertical amplifier.
For this purpose a square wave signal with a very fast rise time
and minimum overshoot should be used, as the sinusoidal
contents cover a wide frequency range.
The built-in calibration generator provides a square wave signal
with a very fast risetime (<4ns), and switch-selectable
frequencies of approx. 1kHz and 1MHz from the output socket
below the CRT screen.
As the squarewave signals are used for probe compensation
adjustments, neither the frequency accuracy nor the pulse
duty factor are of importance and therefore not specified.
The output provides 0.2Vpp ±1% (tr <4ns) for 10:1 probes.
When the Y deflection coefficient is set to 5mV/div, the
calibration voltage corresponds to a vertical display of 4
divisions (10:1 probe).
The output socket has an internal diameter of 4.9mm to
accommodate the internationally accepted shielding tube
diameter of modern Probes and F-series slimline probes. Only
this type of construction ensures the extremely short ground
connections which are essential for an undistorted waveform
reproduction of non-sinusoidal high frequency signals.
Adjustment at 1kHz
The C-trimmer adjustment (low frequency) compensates the
capacitive loading on the oscilloscope input. By this adjustment,
the capacitive division assumes the same ratio as the ohmic
voltage divider to ensure the same division ratio for high and
low frequencies, as for DC. (For 1:1 probes or switchable
probes set to 1:1, this adjustment is neither required nor
possible). A baseline parallel to the horizontal graticule lines is
essential for accurate probe adjustments. (
See also “Trace
rotation TR”).
First Time Operation
