This project introduces the Analog Discovery's™ oscilloscope instrument. An oscilloscope is possibly the most useful, general-purpose tool of all electrical measurement systems. Oscilloscopes (commonly called “scopes” for short) measure voltage as a function of time. Most other devices used in the measurement of electrical signals (such as digital multimeters, or DMMs) make some assumptions as to the time-varying behavior of the signal being measured and provide a single number which supposedly characterizes the signal1. An oscilloscope allows the user to view the time-varying function directly, so no assumptions need to be made as to the actual signal shape.
Oscilloscopes have a wide variety of features, which can be somewhat overwhelming at first. For this reason, we will introduce the Analog Discovery's oscilloscope over the course of several short projects. In this project, we will restrict ourselves to the basics of the way in which voltages are acquired and displayed by the oscilloscope. In this experiment, we will manually connect and disconnect power to an LED and measure the voltage across the LED using our scope.
The oscilloscope instrument on the Analog Discovery uses the same connectors as the Voltmeter instrument. 1+ (the orange wire) is still the assumed positive terminal, and 1- (the orange wire with the white stripe) is still the assumed negative terminal.
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In this project, we will use the same circuit that was created in the Voltmeter Instrument project. Before proceeding through this exercise, set up the circuit according to Step 1 of the Voltmeter project. Your circuit should look similar to the image at the right.
Open WaveForms™ to view the main window.
Click on the Scope icon to open the oscilloscope instrument.
Open the Voltage instrument and turn on power to V+, as described in the Voltage and Voltmeter Instrument projects.
The LED should light up, and the voltage displayed on the oscilloscope waveform window should increase to about 2V.
Unplug the V+ connection from your breadboard (simply pull it out of the board). The LED should go out and the scope should indicate that the diode voltage is zero volts again.
When you are done acquiring data, click on the button.
Connect and disconnect the V+ terminal and verify that the measured voltage still makes sense relative to your changes to the vertical scale of the waveform window.
Connect and disconnect the V+ terminal, and verify that the measured voltage still makes sense relative to your changes to horizontal scale of the waveform window.