How does an oscilloscope function

A digital multimeter helps with exact measurements of discrete signals, thereby making possible readings of up to eight digits of resolution for the voltage, current, or resistance of a signal. An oscilloscope, on the other hand, depicts waveforms in order to show signal strength, wave shape, and the value of a signal.

Oscilloscopes basically measure voltage waves. So on an oscilloscope display, voltage is shown on the Y axis aka vertical axis and time is represented on the X axis horizontal axis. The intensity or brightness of the display is sometimes called the Z axis. A simple oscilloscope typically has three systems — the vertical system, horizontal system, and trigger system. Each system has a role to play when it comes to allowing the oscilloscope to accurately reconstruct a signal.

Sections labeled vertical, horizontal, and trigger make up the front panel. The section also has a vertical beam position knob. This is how the horizontal section controls the time base sweep of the oscilloscope. The trigger section controls the start event of the sweep. The trigger can be made to respond to an internal or external event or to automatically restart after each sweep.

The source and coupling selector switches, the external trigger input EXT Input and level adjustment form the main controls of this section. The trigger controls let us stabilize and display a repeating waveform; a common form of triggering is edge triggering. In this mode, the trigger level and slope controls provide the basic trigger point definition.

The slope control decides if the trigger point is on the rising or the falling edge of a signal, and where on the edge the trigger point occurs is determined by the level control. Many oscilloscopes today also come equipped with a probe.

An oscilloscope probe is essentially a device making a physical and electrical connection between a test point or signal source and the input of an oscilloscope. Depending on one's measurement needs, the connection can be made with a length of wire or an active differential probe.

Earlier, calculation of values using an oscilloscope meant having to manually measure the waveform against the scales built into the screen of the instrument. Modern digital instruments may calculate and display these properties directly. A basic oscilloscope has a bandwidth of up to MHz and is found in almost every design laboratory, education lab, service center and manufacturing environment. An oscilloscope works in pretty much the same way as a CRT television.

For instance, the electron beams in a tv scan back and forth across a screen coated on the back with phosphors. These phosphors light up whenever the beam hits the screen. So when the electron beams fall on the whole screen, they brighten up the phosphors thus forming an image on the screen.

This happens time and again and rather quickly - within the blink of an eye, in fact. Thus we end up seeing moving pictures as opposed to a series of still images.

In an oscilloscope, the electron beams work in the same fashion except that they brighten up the phosphors to form a graph. So when a line is displayed on the screen of an oscilloscope, it is being caused by an electron beam going up and down.

How does an oscilloscope draw a trace? This can be explained with the help of an example. Now your hand is strapped to two electric motors, both of which are in turn connected to electronic circuits that can test signals of different kinds.

Moreover, one of the motors can move your hand in a vertical y direction, even as the other moves the hand in the horizontal x direction. Now say, we connect the x-circuit to an electronic quartz clock. So when the clock ticks, it sends a signal to the x motor thus moving your hand to the right, thereby making you draw a horizontal line. With the x and y circuits connected at the same time, your hand will move across the page, but it will jump up vertically each time the heart beats.

The corners peaks of this wave happen at exactly the same time as the edges in the square wave, so it has the same period as the square wave. You can use the built in measurement functions to confirm these values: Hit the MEASURE button up in the miscellaneous section of the control panel Hit the CH1 button to make sure that channel 1 is the currently active trace.

On the menu on the right side of the screen, select Period by hitting the unlabeled button right next to the item in the menu. This is just like ATM machines at banks. Select the More menu item to see other options.

Keep hitting the More button until the High and Low menu items appear. Select these. You should see measurements on the right side of the screen giving you the period, high voltage and low voltage for the square wave. Now, pull up the same information for channel 2. First you need to remove the measurements and then add the measurements for channel two:.

Often, when looking at signals with an oscilloscope, you're looking at a repeating signal. Triggering allows you to horizontally align repetitions of this signal. When the oscilloscope sees a trigger event, it knows to put a trace onto the screen horizontally aligned with the Trigger Alignment Indicator. A trigger event happens when the voltage goes past the Trigger Level.

This allows a repeating wave to be overlaid on top of itself in such a way that it reinforces previous traces and makes the trace brighter. You can best appreciate the trigger by moving the trigger level to a voltage that the trace never reaches. For example, move the trigger level to -2 volts and you should see the trace dance across the screen.

Now, move the trigger level back to 0 volts for channel 1 and the trace should stabilize. Sometimes, you would like to look at a signal that doesn't happen often, so you would like to capture the event when it does happen and then be able to view the waveform on the screen. In this mode, the oscilloscope continuously tries to capture data and display it on the screen.

Instead, we'd like to have just a single sequence of data on the screen. Do the following:. Need Help? Mountain Time: Shopping Cart 0 items. Product Menu. Today's Deals Forum Desktop Site. All Categories. Development Single Board Comp. Contributors: jimblom. Introduction Have you ever found yourself troubleshooting a circuit, needing more information than a simple multimeter can provide? Favorited Favorite 50 Wish List. Favorited Favorite 49 Wish List. Favorited Favorite 3 Wish List. HAMlab - 10W Only 3 left!

Favorited Favorite 11 Wish List. Basics of O-Scopes The main purpose of an oscilloscope is to graph an electrical signal as it varies over time. Oscilloscope Lexicon Learning how to use an oscilloscope means being introduced to an entire lexicon of terms. Key Oscilloscope Specifications Some scopes are better than others. These characteristics help define how well you might expect a scope to perform: Bandwidth -- Oscilloscopes are most commonly used to measure waveforms which have a defined frequency.

No scope is perfect though: they all have limits as to how fast they can see a signal change. The bandwidth of a scope specifies the range of frequencies it can reliably measure. Digital vs. Analog -- As with most everything electronic, o-scopes can either be analog or digital.

Analog scopes use an electron beam to directly map the input voltage to a display. Digital scopes incorporate microcontrollers, which sample the input signal with an analog-to-digital converter and map that reading to the display.

Generally analog scopes are older, have a lower bandwidth, and less features, but they may have a faster response and look much cooler. Channel Amount -- Many scopes can read more than one signal at a time, displaying them all on the screen simultaneously. Each signal read by a scope is fed into a separate channel. Two to four channel scopes are very common. Sampling Rate -- This characteristic is unique to digital scopes, it defines how many times per second a signal is read. For scopes that have more than one channel, this value may decrease if multiple channels are in use.

Rise Time -- The specified rise time of a scope defines the fastest rising pulse it can measure. The rise time of a scope is very closely related to the bandwidth. Maximum Input Voltage -- Every piece of electronics has its limits when it comes to high voltage.

Scopes should all be rated with a maximum input voltage. If your signal exceeds that voltage, there's a good chance the scope will be damaged. Resolution -- The resolution of a scope represents how precisely it can measure the input voltage.

This value can change as the vertical scale is adjusted. Vertical Sensitivity -- This value represents the minimum and maximum values of your vertical, voltage scale.

This value is listed in volts per div. Time Base -- Time base usually indicates the range of sensitivities on the horizontal, time axis. This value is listed in seconds per div. Input Impedance -- When signal frequencies get very high, even a small impedance resistance, capacitance, or inductance added to a circuit can affect the signal. Every oscilloscope will add a certain impedance to a circuit it's reading, called the input impedance. The impact of input impedance is more apparent when measuring very high frequency signals, and the probe you use may have to help compensate for it.

Anatomy of An O-Scope While no scopes are created exactly equal, they should all share a few similarities that make them function similarly. Using an Oscilloscope The infinite variety of signals out there means you'll never operate an oscilloscope the same way twice. Probe Selection and Setup First off, you'll need to select a probe. Connect the Probe and Turn the Scope On Connect your probe to the first channel on your scope, and turn it on.

Be careful where you place your ground clip when probing a non-isolated circuit eg. When probing a circuit that is grounded to mains earth, make sure to connect your ground clip to the side of the circuit connected to mains earth. If the point the ground clip is connected to has a potential voltage difference you will create a direct short and can damage your circuit, your oscilloscope and possibly yourself! For extra safety when testing mains connected circuits, connect it to power through an isolation transformer.

Purchasing an Oscilloscope Now that you've learned all about this handy tool's features and benefits, it's time to put an oscilloscope on your workbench.

Our recommendations:. Interested in learning more foundational topics? Resources and Going Further With the tools discussed in this tutorial, you should be prepared to start scoping signals of your own. While it's specific to that scope, it still provides a nice overview of what similar scopes are capable of, and how they work.

Going Further Now that you're a practiced oscilloscop-er, what circuit are you going to be debugging? Our EAGLE series of tutorials how to use the freely available software to design your own circuit boards. Recreating Classic Electronics Kits -- If you're in search of a circuit to troubleshoot with a scope, why not make your own version of in-1 electronics kit?

Learn about these signal types and then scope them with your new skills! Or check out these tutorials using an oscilloscope to inspect a signal.

This device allows you to send analog signal from a digital source, like the I2C interface on the Arduino microcontroller. Favorited Favorite 2. Favorited Favorite 7. Favorited Favorite 3. Build a Boss Alarm that alerts you of anyone walking into your office and automatically changes your computer screen.

Favorited Favorite How to combine a piezo sensor, high-value resistor, and an Arduino to create a vibration sensor. Getting started with the SparkFun Proto Pedal. We'll assemble the board, then discuss some of the details of the circuit. Favorited Favorite 8. Favorited Favorite 5. The SparkFun Clock Generator 5P49V60 Qwiic breakout board offers a wide range of customizable frequencies in a wide range of different signal types using a single reference clock.