ECE 110/Equipment/Keysight DSOX1202A

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Introduction

The oscilloscope will be used to visualize time-varying signals, generally voltages. This document specifically relates to the Keysight DSOX1202A Oscilloscope.

Background

From 1000 X-Series Oscilloscopes Data Sheet, p. 3.

An oscilloscope is used to view a voltage waveform on a screen. Modern oscilloscopes are called digital storage oscilloscopes. They use very fast analog-to-digital conversion to record and show voltage waveform data digitally on a built-in monitor screen, typically a liquid crystal display (LCD) flat panel. Digital storage oscilloscopes have display storage, high-accuracy, and flexible triggering. The capture of momentary traces for analysis later is a standard capability of these instruments. This capability makes it possible to view rare or intermittent events and provide a troubleshooting capability that other electronic test equipment cannot.

Additional features of the digital oscilloscope include math functions (e.g. rise time, pulse width, amplitude, addition of two waveforms, subtraction, and averaging), histograms, statistics, persistence maps, signal analysis (e.g. Fourier transforms in the frequency domain), and external data storage (including LAN, WAN, USB, and floppy devices). Digital oscilloscopes are limited principally by their analog input circuitry and sampling frequency, which determines how often the value of the signal is captured (or sampled). For proper waveform display, the highest frequency in a signal must not exceed the Nyquist frequency, which is half the sampling rate of the data acquisition system. Otherwise, distortion referred to as aliasing occurs, which means the higher-frequency components of the signal take on the identity (i.e., alias) of lower-frequency components.

Operation

The oscilloscope has two probes: one for Channel 1 and one for Channel 2. The probes are very expensive (approx. $200 each), so please be careful with them. Each channel has a vertical placement knob which moves the position of the waveform for that channel up and down on the screen. Each channel also has a knob which selects the vertical scale of the waveform in terms of volts per division (see the Analog section on the front panel). Divisions are the visible grid lines on the oscilloscope screen. The knob which sets the horizontal scale in time per division controls both channels (see the Horizontal section on the front panel). The majority of all measurements made in this lab can be performed automatically with the Keysight DSOX1202G oscilloscope.

To see a waveform, press Auto-Scale, which is the white button above the Analog section. The Auto-Scale button will be used more than any other button on the oscilloscope. When you want to capture a waveform on the screen, the first thing to think of is Auto-Scale. This takes the waveform at the input and displays it so that the entire peak-to-peak voltage is displayed over two periods. To measure voltage, push the button marked Quick Meas in the Measure section of the front panel. This will bring up a display of frequency and Pk-Pk at the bottom of the screen. For more choices press the softkey labeled Select: Freq and use the entry knob to make a parameter selection. The entry knob is located just to the left of the Measure section with a black circular arrow above it. For example, selecting Max will produce Measure Max displayed above the next softkey. Pressing this softkey will cause the Max value of the waveform to be displayed.

Notes

• For time-varying signals, the Meas button allows you to access several options. There are two different types of RMS measurement (DC RMS and AC RMS) and for each, there are two different types (N cycles and full screen).
  • The DC RMS gives the root-mean-square voltage calculation for the entire signal. $$\E{V}{RMS}=\sqrt{\frac{1}{T}\int_T(v(\tau))^2}\,d\tau$$
  • The AC RMS gives the root-mean-square voltage calculation for the signal's deviation from its own average. If the average $$\bar{v}$$ is calculated as $$\frac{1}{T}\int_Tv(\tau)\,d\tau$$, then $$\E{V}{RMS,AC}=\sqrt{\frac{1}{T}\int_T(v(\tau)-\bar{v})^2}\,d\tau$$
  • Note that $$\E{V}{RMS}^2=\E{V}{RMS,AC}^2+\bar{v}^2$$

References

• DSOX1202A product page from Keysight
• InfiniiVision 1200 X-Series and EDUX1042A/G Oscilloscopes Users Guide from Keysight
• InfiniiVision 1000 X-Series Oscilloscopes Data Sheet from Keysight