Instruction manual

HB 08-18-2010 11
trigger pulses to produce a trace. This corresponds to AUTO for control 32 of the BK scope.
A difference here that that the TRIG button must be in to freeze the trace with the SWS
scope.
In using the SWS scope display, use MON rather than REC. An enormous amount of
data flows from the scope and if you use REC the storage capacity of SWS will be over
taxed.
6.1 Voltage From 750 Interface
In this section voltages from the SWS signal generator will be examined with the SWS scope.
In the right experiment setup window click the sample V button to open the signal generator
window. Click auto. Drag the scope display icon to the terminals labeled V to open the
scope display. Observe the different signals from the signal generator with the scope display
and thoroughly familiarize yourself with the controls of the SWS scope.
You may have trouble getting a trace with the 3 positive only waveforms from the SWS
signal generator. This may be due to the fact that the default trigger level is 0. Try adjusting
the trigger level for a slightly positive voltage.
A nice feature of the SWS scope is the Smart Cursor. With a good stable trace investigate
investigate this capability.
6.2 SWS Scope and the Voltage Sensor
If you are using the SWS scope to measure voltages in a circuit, use the voltage sensor. To
set this up, drag the scope icon to the voltage sensor icon. The voltage censor is not used in
this lab.
6.3 Lissajous Patterens
Up to now both scopes have been used in the time base mode. In this mode the voltage
applied to the horizontal deflection plates is generated internally in the scope. Both the BK
and the SWS scopes have two-dimensional capability in the X-Y plane. When sine waves
are applied to both the vertical and horizontal inputs of a 2-D scope the resulting trace is
called a Lissajous curve. The form of the curve depends on the frequency ratio and phase
difference of the 2 signals. If the frequency ratio is a rational fraction the curve is closed.
Observe a 5 V 500 Hz Sine wave from the SWS signal generator on the SWS scope in the time
base mode. Click STOP. Click the X-axis input menu button and apply the SWS sine wave
signal to the X-axis of the scope. Use 2 V/div on both the X and Y axes. (Note that with
respect to the X-axis controls of the scope, the 2 buttons that controlled the sweep rate in
the time base mode now control the horizontal gain and are labeled V/div.) What curve do
you see on the screen? What happens if the V/div is changed on one axis? Explain. Leave
the SWS signal on the Y axis of the scope. Use a voltage sensor to input the voltage from
the Wavetek oscillator to the interface. Apply this signal to the X-axis of the SWS scope,
adjusting the X-axis amplification if necessary. Try the frequencies of 500Hz, and multiplies
3/2, 2, etc of that frequency. See if you can get closed curves. It will be impossible to get
steady closed curves because of the frequency and phase drifts between the 2 oscillators but
it should be possible to freeze transient pictures of Lissajous curves by clicking STOP.