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An oscilloscope is displays an electrical voltage over time. It is used to measure periodically recurring events. Furthermore, one-time events can be analyzed by using single shot measurements. An inexpensive alternative to stand alone devices are usb oscilloscopes.
An oscilloscope is an indispensable device for the development or failure analysis of circuits. Arbitrary voltage signals can be measured over time. An oscilloscope is also very helpful for error analysis. The voltage curves can be used to investigate errors in all details. This enables the developer to narrow down the error and reach the target more quickly. The device thus promotes an accurate analysis. In addition to the graphical representation, the developer has numerous mathematical functions at his disposal. This enables the developer to examine the signal exactly. A well-known method is FFT analysis. The signal is broken down into its individual spectral components and thus any interference frequencies can be detected. This function is represented by software and is also available with USB oscilloscopes. But also other functions like the display of the mean value or min and max values can be helpful for the analysis. Saving images also makes analysis easier.
A USB oscilloscope is a measuring instrument that is operated via a USB port and requires a computer or tablet computer. The USB oscilloscope consists of an acquisition unit and a PC that displays the data through a graphical user interface. The USB oscilloscope has one or more analog channels, digital channels if necessary, and buttons or switches for operation. USB oscilloscopes stand out from classic oscilloscopes in two ways. On the one hand, they are usually much less expensive because the graphic display is done by the host PC. A USB oscilloscope essentially only requires an AD converter and a USB interface. Further features are realized via the corresponding software. On the other hand, USB oscilloscopes are usually very compact and can be used in places that are difficult to access. Especially in combination with a tablet PC they are more mobile than conventional oscilloscopes.
Key factors for usb oscilloscopes
What exactly does is important when buying an USB oscilloscope? This depends strongly on what exactly is needed. The intended use also plays a decisive role. The most important feature is the number of channels you want to capture simultaneously. In addition, the achievable analog bandwidth plays a role. Another parameter is the resolution of the conversion. Further features are supported platforms, software and small tft displays for mobile use.
Number of channels
For simple applications, one channel might be enough. Howevery, in most cases you should look for at least two input channels. This means that your usb oscilloscope can monitor two analog signals at the same time. Furthermore, some oscilloscope support additional digital channels. Digital channels are interpreted as zero or one, according to their voltage level.
The analog bandwidth is very important. It indicates which frequencies can be captured by the device. The analog bandwidth is given in kHz or MHz and represents the highest sine wave frequency which can be observed by the oscilloscope. If you look at abitrary or rectangular signals, please note that these signals have sine wave components of 10x the base frequency. If you want to monitor a 10 kHz rectangular signal, your bandwidth should be at least 100 kHz.
The sample rate determines how many digital samples per second are taken. The value is independent of the bandwidth. It should be at least two times the bandwidth.
The finer the resolution, the better the signal can be resolved. A high resolution is desirable, especially for investigations of low signals. The resolution is often given in Bit. A Resolution of 8 Bits means the scope displays 2^8=256 different signal levels.
Gain / Voltage Range Gain settings allow to change the input range of the scope. Usually the input range lies between some Millivolts and several Volts.
If you want to use your scope as stand alone device, you should buy a scope with display. If this is not important to you, you might think about a displayless version.
The sample memory determines how many samples can be recorded in one shot. More memory is better.
Platforms and software
All usb scopes have supporting software. Some are only for Windows, some may support Linux or Mac. Have a look at the description.
Below the best popular and inexpensive USB oscilloscopes are listed. The most important parameters such as number of channels, analog bandwidth, sampling rate and other features are given in the overview. Popular manufacturers are SainSmart and Hantek .
Review of best USB oscilloscopes.
- Dual Channel
- 20 MHz
This scope by Hantek is a displayless usb device. It supports two input channels and has an analog bandwidth of 20 Mhz. The maximum sampling rate is 48 MSa/s with a resolution of 8 Bit per channel. The input range is selectable in 8 Steps between 20mV and 5V. It supports XY-Mode (twodimensional display of signals) and can be triggered by an external signal (Ext Input). The software supports the usual mathematical functions like FFT, Add, Subtract, ... . You need a Windows Computer for it. Two probes and USB cable are included.
- Single Channel
- 200 kHz
This device by SainSmart is more a handheld scope than a USB scope. It features only one input channel with 200kHz Bandwidth. The sampling frequency is 1 MSample per second. It can store 8000 samples in memory. The analog input range is selectable between 20mV to 10V. The scope has a built in display (320 x 240 pixels) and allows mobile use. Furthermore, the device has a signal output to generate square, sine, triangle or sawtooth waveforms. The DSO 211 has 8MB USB flash disk memory. The measured signals can be stored on this flash disk memory and can be accessed by a Micro USB connector. Ships with one probe.
- 2 Channels
- 1 MHz
- 10 MSa/s
This SainSmart handheld scope features two analog input channels, having a bandwidth of 1 Mhz. Signals can be samples at 10 MSa/s into the internal 8k memory. It has 8MB of flash memory, accessable by micro USB. Battery capacity is 500 mAh, display resolution is 320 x 240 pixels. As all SainSmart devices, it has a waveform output to generate common signals. The device is a good compromise between price and capability. It comes with one probe.
- 8 Channels
- 100 kHz
- 2.4 MSa/s
This usb oscilloscope from Hantek is designed for automotive diagnostics. It features 8 input channels with an analog bandwidth of 100 kHz. The voltage Range can be set up from 10mV/div to 100V/div, using appropriate probes. The device does not come with a display, it requires a Windows software. It is designed to be used on a laptop. The software has comprehensive features such as voltage measurement maximum amplitude, overshoot, frequency measurements, rise / fall time and so on. Hantek ships the device with 8 test lines, one probes, USB line and a quality carry bag for transportation.
- 4 Channels
- 8 MHz
- 72 MSa/s
The high end version from SainSmart is this DSO203 device and one of their best models. It supports 4 input channels. Two of them are for analog signals, two channels are digital channels only. The analog bandwidth is 8 MHz with a maximum sampling rate of 72 MSa/s. The sample memory is 4k, flash memory is 8MB. The display has a higher resolution than other SainSmart devices (400x240). Furthermore, battery capacity is increased to 1000mAh for better mobile use. Input resistance is 1MOhm for all channels. Ships with battery and two probes.