Introduction to Oscilloscopes
You use an oscilloscope to display electrical signals as waveforms. A waveform is a graphical
representation of a wave. An oscilloscope receives an electrical signal and converts it into a waveform.
The waveform shows the change in voltage with time on the oscilloscope display screen.
You can use an oscilloscope to determine the following:
• The frequency of an oscillating signal
• The malfunctioning component in an electrical circuit
• Whether the signal is direct current (DC) or alternating current (AC)
• What part of the signal is noise
You can also use oscilloscopes to measure electrical signals in response to physical stimuli, such as
sound, mechanical stress, pressure, light, or heat. For example, a television technician can use an
oscilloscope to measure signals from a television circuit board while a medical researcher can use an
oscilloscope to measure brain waves.
Probe Compensation
When you attach a passive voltage attenuation probe to an oscilloscope, the capacitances of both the
probe cable and the oscilloscope’s input combine. This combined capacitance must match the
capacitance of the input attenuation circuit of the probe. You must balance these capacitive effects
between the probe and the oscilloscope to get a flat step response. Probes are designed to match the
inputs of specific oscilloscope models. However, there are slight variations between oscilloscopes and
even between different input channels in an oscilloscope. To minimize these variations, attenuating
passive probes (10X and 100X probes) have built-in compensation networks. You need to adjust the
network to compensate the probe for the oscilloscope channel that you are using. You must
compensate a passive voltage attenuation probe every time you change a probe/channel connection
of your oscilloscope. This ensures that the probe accurately transfers the signal from a signal source
to the oscilloscope.
You should observe a square waveform displayed on the oscilloscope similar to the waveform shown
in Figure if probe is compensated properly.
However, the waveform could also have distorted corners similar to the waveforms shown in Figure
below
Vertical Control Knobs
VOLTS/DIV knob
You use the VOLTS/DIV knob to set and change the vertical voltage scale for the displayed waveform.
Consider this example. If the channel 1 volts/div setting on the displayed readout is CH1 5.00V, then
each vertical division for channel 1 on the graticule represents 5 Volts and the entire graticule of 8
vertical divisions can display 40 Volts peak-to-peak. You use this menu option to select the incremental
sequence of the VOLTS/DIV knob.
POSITION knob
You use the POSITION knob of the VERTICAL controls of a given channel to move the displayed
waveform up or down on the display.
HORIZONTAL Control Knobs
SEC/DIV knob
You use the SEC/DIV knob to control a waveform’s horizontal time scale. The horizontal center of the
display is the time reference for expanding and compressing waveforms. If the sec/div setting is 100
milliseconds (ms), then each horizontal division on the graticule represents 100 ms and the entire
graticule of 10 horizontal divisions can display 1000 ms or 1 second.
POSITION knob
You use the POSITION knob of the HORIZONTAL controls to move the displayed waveform to the
left or the right of the horizontal center of the graticule.
