Instruction manual

HB 08-18-2010 10

up most of the screen and horizontally there is about one cycle of the input waveform on the

screen. Use the calibration of the VOLTS/DIV control and the horizontal grid lines on the

screen to determine the peak to peak voltage of the triangular wave. Use the calibration of

the TIME/DIV control and the vertical grid lines on the screen to determine the period of

the wave. For both of these measurements judicious use of both the horizontal and vertical

position controls will enable you to utilize the ﬁner markings on some of the grid lines of the

screen. The amplitude of the output of the Wavetek is not calibrated. You are using the

scope to measure this amplitude. The frequency output of the Wavetek is calibrated and

you should compare the Wavetek’s stated frequency with your period measurement.

5.6 Scope Probes

In this experiment the function generator is connected to the scope by a cable with connectors

on both ends. Very often, voltages in a circuit are of interest and a scope probe is used. This

is a cable with a connector on one end for plugging into the scope input. The other end of

the probe cable has an electrode for touching the point in the circuit whose voltage waveform

is desired. There is a clip for making a connection to ground. Probes often attenuate the

signal by a factor of 10 or a 100, but if they do, the resistance loading they present to the

circuit increases by a factor of 10 or a 100. Remember that in connecting a voltage measuring

device to a circuit, the higher the resistance of this device, the better. A probe is not used

in this lab.

6 Using The SWS Oscilloscope

One of the displays available with SWS is the oscilloscope. This is not actually an oscilloscope

but software that closely mimics an oscilloscope. In some respects the SWS scope is a more

powerful diagnostic tool than the BK scope. In particular:

1. There are 3 vertical inputs each of which has its own trace. (Three voltages can be

observed simultaneously as a function of time.) The 3 traces have diﬀerent colors. The

input for each trace is selected by an input menu button.

2. This scope is a storage scope. When you stop monitoring data the last trace is stored

for further use.

3. There is a smart cursor which is used in a similar way as in the graph display.

On the other hand, the BK scope is a much faster scope. The highest frequency you can

examine with the BK scope is 30 MHz. With the SWS scope the highest frequency is 10 kHz.

The other main diﬀerence between using the BK and SWS scopes is that in the SWS scope

the controls are icon buttons, and a slider is used for the trigger level and slope. See page

178 of the SWS manual for a description of adjusting the trigger level and slope. The picture

in the manual does not show this slider adequately. It is a small triangle in a vertical strip

at the very left of the scope screen. The default trigger voltage is 0 with positive slope.

There are only 2 trigger options in the SWS scope. The default is with the button at

the bottom of the scope display labeled TRIG in the in position. In this mode there must

be an appropriate input signal for a trace to be observed. This corresponds to NORMAL

for control 32 of the BK scope. If you are having trouble ﬁnding a trace, click the TRIG

button. With this button “out” the time base oscillator is free running and does not need