BK Precision 5105B, Instruction Manual, Page: 19 / 48

19
Subject to change without notice
AUTOSET
For specific information consult ”Controls and Readout“ AUTO-
SET
11
.
The following description is valid for both analog and DSO
modes. AUTOSET does not change from analog to DSO mode
or vice versa. If in DSO mode the modes ”Roll“, ”Envelope“ or
”Average“ (ACQUIRE) are present or the trigger mode „Sing-
le“ (MODE) is selected, theses modes will be switched off as
AUTOSET always switches to ”Refresh“ acquistion. The signal
to be displayed must meet the amplitude and frequency
requirements of automatic triggering, to enable a useful
automatic instrument setting.
All controls except for the POWER switch are electronically
scanned, all functions can also be controlled by the
microcomputer, i.e. also via the interfaces.
This is a precondition for AUTOSET as this function must be
able to control all functions independent of control settings.
AUTOSET will always switch to YT mode, but preserve the
previous selection of CH1, CH2 or dual trace; ADD or XY modes
will be switched to dual trace Yt.
Automatic setting of the vertical sensitivities and the time base
will present a display within 6 cm height (4 cm per signal in
dual trace) and about 2 signal periods. This is true for signals
not differing too much from a 1:1 duty cycle. For signals
containing several frequencies like video signals the display
may be any.
Initiating the AUTOSET function will set the following operating
conditions:
–
last selection of ac or DC coupling
– internal triggering
– automatic triggering
– trigger level set to the center of its range
– calibrated Y sensitivities
– calibrated time base
– AC or DC trigger coupling unmodified
– HF trigger coupling switched to DC
– LF or Noise Reject filters left
– X magnifier switched off
– Y and X positioning automatic
Please note:
For pulse signals with duty cycles approaching 400:1 no
automatic signal display will be possible.
In such cases switch to normal trigger mode and set the trigger
position about 5 mm above the centre. If the trigger LED will
then light up a trigger is generated and the time base is
operating. In order to obtain a visible display it may be
necessary to change the time base and V/DIV settings.
Depending on the duty cycle and the frequency the signal may
still remain invisible. This applies only to analog mode. In DSO
mode the trace is always of equal brightness because not the
signal is shown but a low frequency construction of it, also,
there is no information in the trace intensity.
C o m p o n e n t T e s t e r
Component Tester
Specific information can be found in ”Controls and Readout“
under COMPONENT/PROBE and COMPONENT TESTER
.
The scope has a built-in component tester. The test object is
connected with 4 mm banana plugs. In this mode the Y
amplifiers and the time base are turned off. Only individual
components may be tested, i.e. they must not be part of a
circuit, if voltages are to be applied to the BNC connectors. If
the components are part of a circuit this must be deenergized
and disconnected from safety ground. Except for the two test
leads there may be no further connection between scope and
component. (See ”Tests within a circuit“). As described in
section ”Safety“ all ground connections of the scope are
connected to safety ground including those of the component
tester. As long as individual components are tested this is of
no consequence.
The display can only be affected by the controls contained in
the FOCUS/TRACE menu: A-Int., Focus, Trace rotation, HORI-
ZONTAL position.
If components are to be tested which are parts of a circuit or
an instrument those circuits resp. instruments must first be
deenergized. If they are connected to the mains they must be
unplugged. This will prevent a connection between scope and
circuit via the safety ground which may affect the
measurement.
STOP
Do not test charged capacitors.
The principle of the test is very simple: a sine wave generator
within the scope generates a 50 Hz ±10 % voltage which is
applied to a series connection of the test object and a resistor
within the scope. The sine wave proper deflects in X direction,
the voltage across the resistor which is proportional to the
test current deflects in Y direction.
If the object contains neither capacitors nor inductors, there
will be no phase shift between voltage and current, so a straight
line will show up which will be more or less slanted, depending
on the value of the object’s resistance, covering appr. 20 to
4.7 K . If there is a short the trace will be vertical, i.e. (almost)
no voltage produces already high current. A horizontal line
will thus indicate an open, there is only voltage but no cur-
rent.
Capacitors or inductors will create ellipses. The impedance
may be calculated from the ellipse’s geometric dimensions.
Capacitors of appr. 0.1 µF to 1000 µF will be indicated.
– An ellipse with its longer axis horizontal indicates a high
impedance (low capacitance or high inductance)
– An ellipse with its longer axis vertical will indicate a low
impedance (high capacitance or low inductance)
– A slanted ellipse will indicate a lossy capacitor or inductor.
Semiconductors will show their diode characteristics, however,
only 20 Vpp are available, so the forward and reverse
characteristics can only be displayed up to 10 Vp in each
direction. The test is a two-terminal test ,hence it is not
possible to measure e.g. the current gain of a transistor. One
can only test B-C, B-E, and C-E. The test current is only a few
mA, so the test will not harm ordinary semiconductors.