Instruction manual

HB 08-18-2010 9
1. the VOLTS/DIV controls are changed (15 and 16)?
2. the TIME/DIV controls are changed (23 and 26)?
3. the trigger level (33) voltage is changed (33)? Note that if the trigger voltage is set too
high or too low the trace does not “freeze” but “runs” to the right or the left if the
trigger coupling switch is on AUTO.
4. With the trigger COUPLING switch in the NORMal mode, can you make the trace
disappear by rotating the TRIG LEVEL knob (33) both ways? Explain.
5. the triggering slope is changed from + to − (pull control 33).
6. the position controls 17 and 27 are changed?
The controls you have just used are the ones most frequently employed in adjusting the
trace.
It is instructive to look at a low frequency signal from the Wavetek oscillator. If the
frequency is appropriate, the time development of a trace as shown in Fig. 4 can be followed.
Set the frequency of the Wavetek oscillator to about 5 Hz and the time base to 50 ms.
Observe the development of the trace carefully and note the effect of changing the trigger
parameters. Change the sweep speed one click to 20 ms and increase the frequency of the
Wavetek function generator until about the same number of cycles appear on the scope.
Keep doing this until the trace becomes continuous.
5.3 Other Waveforms and Functions
• Observe square and triangular waveforms from the Wavetek by pushing the appropriate
buttons. The frequency is not critical, but around 1 kHz works well.
• Look at all the waveforms and observe what happens to the waveforms when you pull
out the Wavetek knob marked DUTY (short for duty cycle) and rotate the knob CW
and CCW. Push in the DUTY knob.
• Pull out the Wavetek OFFSET knob. Change the CH1 AC-GND-DC (13) switch from
AC to DC and rotate the OFFSET knob. What does the trace do? What does the
trace do if you change back to AC? Can you figure out how to measure the amount of
DC bias a periodic signal has? (The DC bias of a voltage signal is its average value.)
5.4 Maximum Input Voltage
An important specification of a scope is the maximum input voltage that is permitted. For
the BK scope this is ± 400 V. A small AC voltage riding on a large DC voltage can be
examined by putting the input switch (13) on AC. The average voltage of the input voltage
is removed by the input capacitor and the gain of the scope can be utilized to vet the AC
part of the signal.
5.5 Measuring Waveform Parameters
A useful function of a scope is to measure the peak to peak voltage and period of a voltage
waveform. Display a 1 kHz triangular wave on the scope. Controls 16 and 26 must be fully
CW in their calibrated positions. Adjust the other controls so that vertically the trace takes