A digital oscilloscope measures the change of voltage over time. It is an essential tool for signal analysis in a wide range of electronic applications.
Unlike a multimeter, which only shows you a number, an oscilloscope plots a waveform that is much more informative than a figure. You can analyse signal behaviour to check if everything is working as it should.
Oscilloscopes are especially useful for analysing high frequency signals that a multimeter can’t keep up with.
Digital oscilloscopes offer many advantages over older analog oscilloscopes, a key one being the ability to store and analyse waveforms even after you’ve disconnected the probe.
Digital oscilloscopes are used in virtually all electronics manufacturing and testing environments.
They are essential for testing and calibrating things like smartphones, circuit boards, televisions and even in cars where they are used to test various sensors and electrical systems (which modern cars have a lot of).
Another common use of digital oscilloscopes is in troubleshooting electrical devices. By analysing the signal waveform, a technician can precisely diagnose malfunctioning electronic equipment.
In this buying guide, we review the best digital oscilloscopes and help you find the right one for your needs. But first, a few things to keep in mind when you are shopping for a digital oscilloscope.
- Read also: Best nitrogen regulators
What to Look for When Buying A Digital Oscilloscope?
The first thing to check when you are shopping for an oscilloscope is the bandwidth. This is the frequency range of the oscilloscope. That is, the maximum frequency it can measure.
But it’s not as simple as selecting a max frequency that matches the highest frequencies of the signals you want to test.
Use the ‘five times rule’ to select the right bandwidth. Your selected oscilloscope’s bandwidth should be five times you circuit’s max frequency.
This maintains the measurement error at ±2% to ensure as much precision as possible.
If your highest circuit frequency is 20MHz, you’ll need an oscilloscope with a 100MHz bandwidth.
On that note, also make sure the probe has the same bandwidth as the oscilloscope or higher.
2) Number of channels
More channels, or inputs, give you more flexibility when it comes to testing circuitry. With two channels, you can test and compare the input and output signal.
With four channels, you can compare multiple signals.
Having more channels can save you time when you need to test and compare many different signals. But it also adds to the price.
3) Sample rate
An oscilloscope’s sample rate – how often it samples the signal – is similar to a camera’s frame rate. It determines the resolution of the waveform.
A higher sample rate produces a more detailed waveform, which allows better analysis and debugging.
Sample rate is indicated in Samples per second (S/s) or gigasamples per second (GS/s).
A good entry-level oscilloscope should have a sample rate of at least 1 GS/s while a pricier model will provide a sample rate of 5-10 GS/s.
Similar to bandwidth, you should get an oscilloscope with a sample rate at least 5 times your highest frequency. This allows you to capture any periodic glitches.
Note that a higher sample rate fills up the memory quicker.
4) Rise time
Fast rise time is essential for accuracy especially in situations where you need to take time measurements.
Use the ‘five times rule’ to pick the best rise time. The oscilloscope should have a rise time five times as fast as your signal’s fastest rise time.
If you are measuring a signal with a 2-nsec rise time, the most accurate oscilloscope to use is one with a 0.4-nsec (400-psec) or faster rise time.
Triggering stabilises the waveform so that you can make meaningful analysis. You can use the trigger to tell the oscilloscope at what point to start measuring the signal.
Check the trigger options available in the oscilloscope that you want to buy. More options give you added measuring versatility especially when dealing with signals that are tricky to measure.
The most common types of triggering are edge and pulse width triggering.
Additional types include interval, window, window pulse width, level dropout, runt and logic triggering.
I highly recommend getting an oscilloscope that comes with its own probes. This ensures compatibility. If you have to buy probes separately, order them from the same manufacturer if possible.
Here’s what to consider when selecting the right probes for your oscilloscope.
- Bandwidth: Should be similar to or higher than the scope bandwidth. That means it should be at least 5 times higher than your circuitry’s highest signal frequency.
- Attenuation ratio: This depends on the voltage amounts you are dealing with. 1x probes (1:1 ratio, no attenuation) are ideal for low-frequency applications. But most probes are 10X, meaning that the signal to the oscilloscope is a tenth of what the probe receives from the circuity (10:1 ratio). A high attenuation ratio probe – e.g. 100:1 – allows you to measure higher voltages.
- Loading: In a theoretical world, a zero loading probe produces the most accurate results. But zero loading is not possible so try to get a probe with very low loading.
- Types: Passive probes use passive components and don’t need power. They are cheaper, last long and have high input resistance. But they have high input capacitance. Active probes require power. They have higher bandwidth, low input capacitance and high input resistance. On the downside, they cost more and don’t last as long. Two other types of probes are differential and current probes.
7) Other considerations
- Check the memory depth, which determines how much signal you can capture at a certain sample rate. Higher memory depth allows you to capture more signal at a high sample rate.
- Automatic measurements of amplitude, rise/fall time and time among other parameters. This saves you a lot of time.
- Mathematical functions that allow advanced measurements and analysis while saving you time.
- Size and design. A benchtop digital oscilloscope is ideal in a lab environment where portability is not essential. But if you are planning to do move around with the oscilloscope or do some field work with it, a compact and more portable model will serve you better.
- Large and bright display. A good quality display will produce a brighter image and will be easier on your eyes. Some modern oscilloscopes with a touch display for easier and faster control of various parameters.
- Environmental requirements. Check the manufacturer recommended temperature and humidity operating range. This ensures the oscilloscope maintains its accuracy.
- USB vs. standalone oscilloscope. Standalone or benchtop oscilloscopes are the most common. But if you want something you can carry around, get a USB oscilloscope. It hooks up to a computer and uses its screen as the interface.
The Best Digital Oscilloscopes Reviews
1. Hantek DSO5102P Digital Oscilloscope
With a 100MHz bandwidth, the Hantek DSO5102P digital oscilloscope is ideal for testing low and mid-range frequency signals.
It has two channels, which allows you to view and analyse two waveforms simultaneously.
As for the performance specs, here’s what you need to know.
- 5ns rise time
- 1GSa/s sampling rate
- 40K memory depth
- 1MΩ input impedance
- 0-50℃ operating temperature range
The oscilloscope provides a fair amount of versatility, allowing you to carry out different kinds of measurements and analysis.
For instance, it offers 6 types of trigger including pulse, slope, edge and over time. It also has several math functions that include x, +, -, ÷ and FFT (fast Fourier transform).
Another time-saving feature is automatic measurement of various parameters including frequency, mean, period, rise time, fall time and others.
Measurements and waveforms are displayed on the bright 7” TFT screen with all the buttons you need on the side.
At the bottom below the screen is a USB port when you can plug in a USB drive and save screen captures to it for later analysis.
You can also connect it to a computer via a port at the rear, though some customers have had trouble getting to link to a PC (check compatibility requirements including version of Windows).
The oscilloscope comes with a pair of probes.
2. Siglent Technologies SDS1202X-E 200 mhz Digital Oscilloscope
If you deal with higher frequencies, get this 200MHz digital oscilloscope. It allows you to accurately test frequencies up to 40MHz.
It’s an entry-level digital oscilloscope so it’s fairly limited in terms of specs and functionality.
Here are the most important specs.
- 1 GSa/s sampling rate
- 14 Mpts recording length
- 400, 000 frames/sec waveform capture rate
- Two channels
- 800×480 7” TFT display
The Siglent digital oscilloscope is designed with beginners in mind. To that end, it comes with several helpful features to help you get acquainted with all the buttons and controls.
One of the most helpful is the help screen. Press and hold a button and a help screen pops up telling you what it does. This will significantly shorten your learning curve.
Another helpful feature are the one-button shortcuts that provide quick access to various functions such as measure, roll, clear sweep, print and zoom.
The oscilloscope offers several types of triggering including serial bus triggering as well as edge, slope, window and other common triggers.
It also provides 8 mathematical functions including FFT, square root, differentiation and integration.
As for connectivity, you have two options: Ethernet and USB.
You can use Ethernet though it’s slow and requires a long and tedious set up process including downloading software.
USB is faster and easier to set up.
The oscilloscope comes with two probes.
3. Hantek DSO5202P Digital Oscilloscope
This is another good choice if you are looking for a 200Mhz oscilloscope. It’s almost similar to the Hantek DSO5102P I’ve just reviewed above with the main difference being the higher frequency.
With the Hantek DSO5202P, you can test frequencies up to 40Mhz.
Here are other important specs.
- 1GSa/s sample rate
- 1MΩ input impedance
- 40K record length
- 800×480 7” colour display
- 2 channels
Most of the other functions in the DSO5202P are the same ones in the DSO5102P: several trigger modes, automatic measurements, several mathematical functions including FFT and ‘save to USB’.
Overall, this a good upgrade from basic oscilloscopes. The higher bandwidth should give you much better mileage and versatility.
4. Rigol DS1054Z Oscilloscope
The Rigol DS1054Z oscilloscope has a lower bandwidth but makes up for it with two extra channels compared to the other oscilloscopes.
It also comes with a lot more features that provide more functionality and versatility.
Here are the main specs.
- 4 channels
- 12 Mpts memory (expandable to 24 Mpts)
- 30,000 wfms/s Waveform capture rate
- 7” TFT screen
- 1 GS/s sampling rate
With four channels to play with, you can analyse multiple waveforms at the same time. This makes it easier and faster to diagnose and test complex circuitry.
The oscilloscope provides advanced triggering options, multi-level intensity graded display and various mathematical functions for signal calculations.
In terms of connectivity, you can plug in a USB device to store screen captures or use the USB cable to connect the oscilloscope to your computer.
For an entry-level oscilloscope, the Rigol DS1054Z offers a lot more than you get in most basic models.
Note however that some of the advanced features are available in a trial mode. After a few days, you’ll have to pay for them if you want to keep using them.
The Rigol DS1054Z digital oscilloscope comes with 4 probes.
5. Pico Technology PicoScope 2204A USB Oscilloscope
This is a great choice if you are looking for a highly portable USB oscilloscope. The PicoScope plugs into your laptop or desktop computer. You then access the waveforms and controls from your computer’s screen.
Like other USB oscilloscopes, it’s not quite as capable as a full size standalone scope. The 10Mhz bandwidth is helpful only for low-frequency electronics such as audio recorders.
It also has a lower sampling rate (100 MS/s), lower buffer memory (8 kS) and slower rise time (35 ns).
The oscilloscope has two channels that let you view and analyse two waveforms at the same time.
To use the PicoScope with your computer, you’ll need to download the companion software, which is available for Windows, Max and Linux devices.
You can then access features like serial decoding, mask limiting, automated measurements, math functions and other features.
The PicoScope oscilloscope comes with probes.