PicoScope Offers Bandwidth with Versatility
James Anderton posted on August 02, 2017 | 4248 views

The benchtop oscilloscope has been an indispensable tool for circuit developers and test/repair technicians for more than half a century. It was a classic analog device, with magnetic/electrostatic deflection of electron beams in a glass tube remaining the key technology until the emergence of high speed A/D converters, memory devices and flat screen technology in the mid ‘90s.

Pico Technology debuted the world’s first mainstream PC connected ‘scope in 1991, effectively creating a new category for “screenless” oscilloscopes that leverage the other universal piece of equipment on every bench: the laptop. Using the big, high-res display built into laptop technology wasn’t just a way to get more information onto a bigger screen, it had a very useful knock-on effect—the absence of a display and its associated hardware/software meant that the product cost was dedicated to signal detection and processing, where the real performance is in scope technology.

ENGINEERING.com tested a PicoScope 5444B model and found considerable performance and feature content in a deceptively small package.

The 5444B, despite it’s unassuming paperback-book size is not a stripped down ‘scope. The USB 2.0 unit ships with an integral arbitrary waveform generator, multiple triggering modes, Fast Fourier transform spectrum analysis and statistics tools as well as serial decoding for I2C, SPI, UART, LIN and FlexRay for the automotive community.

The Model 5444B we tested shipped in ESD-resistant packaging and is notable as a complete kit; the four-channel ‘scope includes four probes, each with a full accessory set, two certified high-speed USB cables and a power supply with a neat clip-on adapter plug that makes the unit compatible with mains supplies anywhere in the world. In two channel mode, the unit can self power through the USB connection for added portability.

The unit is nominally 5VDC powered and connections are made through standard BNC jacks that are usefully color-coded for each channel. Floating ground fanatics will find a convenient earthing screw at the back of the unit.

 

Fast Sampling Rates, Mask Limit Testing

Bandwidth is a generous 200 MHz and for the large body of digital users, the unit carries a lot of punch in its small package. 8-, 12-,14-, 15- and 16-bit resolution is significant, and the critical sampling rates range from a lightning fast 1GS/s at 8 bits resolution to 62.5 MS/s at 16bits. A 512 MS buffer memory additionally keeps anything hiding in the signal from evading the engineer’s notice. High sample rates require serious memory, and the Pico unit uses a 512MS buffer to allow testing at maximum sampling speed over long durations.

Mask limit testing is a surprising feature in the 500 Series. Mask testing is a signal quality evaluation technique where the user compares the test signal to a predefined “mask” to count hits or violations, a useful addition for bench or field troubleshooting.

Transients are frequently as fleeting as they are annoying, and the 5444B captures them in a 10,000-waveform buffer memory, meaning there’s no need to repetitively rerun a test to spot a glitch.

Sensitivity is a natural concern in a compact unit like the 5444B, but careful front-end design allows Pico to claim 2mV/div at full resolution and a very high 100uV/div rating in 14-bit mode with zoom. High sensitivity, with a capture rate of 130,0000 waveforms per second, suggests that few transients will escape this ‘scope.

 

Fast Fourier Spectrum Analyser Included


While the classic amplitude vs. time display is still the most common way to analyse signals, Pico’s FFT spectrum analyser includes an amplitude vs. frequency “spectrum view” that’s great for rooting out noise or transients that don’t repeatedly occur in the time domain. This mode will be especially useful for the analog community working with amplifiers, filters and oscillators. A wide range of options are available in this mode, including linear, log or log/log scaling with instantaneous, average or peak hold display over a number of spectrum bands.

 

Advanced Triggering

Many digital ‘scopes use an analog-derived triggering architecture, introducing errors that have historically made the full bandwidth of a ‘scope suspect at the limits. Pico uses a fully digital triggering strategy that gives away nothing in speed, with a less than 2 µs rearm delay. Combined with a segmented memory, this lets users capture up to 10,000 waveforms in a 20ms burst. Pulse width, windowed, logic and dropout triggers are available as well as a runt pulse mode for signals that don’t reach a valid high or low logic state.

 

Simplified Serial Bus Decoding and Protocol Analysis

There are a wide variety of serial bus standards in common use both for device-to-device data handling and within a board. IC’s in particular enjoy a simplified architecture and lower pin count using serial systems, but the data flow, although slower, isn’t easy to analyse in real time.

Bit counting is time consuming and error prone, so Pico has included built-in decoding and analysis capability for common serial standards such as 1-Wire, ARINC 429, CAN and CAN FD, DCC, DMX512, Ethernet 10Base-T and 100Base-TX,  FlexRay, I²C, I²S, LIN, Modbus, PS/2, SENT, SPI, UART (RS-232 / RS-422 / RS-485), and USB 1.1 . The company adds others regularly and offers the upgrades free of charge to Pico ‘scope users.


Serial decoding is possible in multiple modes: In Graph format, In Table format or both at once. The In Graph mode displays the data stream alongside the analog waveform and highlights error frames. These can be zoomed and compared to analog channels to detect timing and signal quality issues when troubleshooting data quality problems.

The In Table format lists decoded frames, showing data and including all flags and identifiers. To separate good and suspect data, the user can define filtering conditions including filters for frames with specified properties. A statistics option uncovers possible issues with “housekeeping” details about frame times and voltage levels.

Analysis of serial data is typically a “needle in the haystack” problem. There’s a lot of data, perhaps thousands of packets, and most of it is not the source of the issue. Pico addresses this challenge with several tools.

Search lets the user define search criteria and the software highlights packets that meet the defined criteria. A similar mode, Filter, screens for specific user defined conditions. Users needing a deeper dive can use the Statistics function to show detailed voltage and timing information from each packet, a useful option for reliability testing.

To make the analysis more readable (and the results understandable to everyone in the lab) Link File lets the user tag hexadecimal values with their macro system meaning. If that address is monitoring system pressure, for example, it’s not necessary to move the data to an outside application to make it presentable on a screen capture or spreadsheet. In fact, Pico allows a user to import a spreadsheet as needed, a very useful feature when used with the Export function when data must be presented in a form readable for reports or PowerPoint presentations.

Is the Software the Secret?

The key to the high performance of the 5444B is as much in the software as the diminutive ‘scope, and in any high-performance application like this, high-overhead, complex code could be expected. ENGINEERING.com tested PicoScope 6 software by loading from the supplied disc into a pedestrian HP Pavilion laptop, representing a typical office unit.

Specs were: Intel Core i5-6200U (2.3 GHz, 3 MB cache, 2 cores) with Integrated Intel HD Graphics 520, 8 GB DDR4-2133 SDRAM (2 x 4 GB) RAM; 1 TB 5400 rpm SATA Hard Drive.

This is a sub $500 laptop, but the software loaded quickly and easily, without extensive user interaction. It contains the usual user guide and thankfully uses a simple, stripped down GUI that lets any user that can handle a bench ‘scope start working immediately.

We tested it the way many users will; by ignoring the tutorials and simply hooking up the hardware and probing. It works like a conventional ‘scope and uses drop down menus familiar to anyone who uses MS Office products. The extra features allowing printing, massaging and sharing waveform data are also mercifully simple. If you just want to get it done, you won’t need special training to use the 5444B straight out of the box.

PicoScope 6 runs on Windows, Mac and Linux operating systems and power users can tap a software development kit that allows users to write their own code. Drivers are included for MS Windows, Apple (OS X) and Linux, including Raspberry Pi and BeagleBone.

A typical use for custom code would be for communication with popular third-party packages like MS Excel, National Instruments LabVIEW and MathWorks MATLAB. The Pico website hosts a developer community that can help with the process.

So, what does all this capability cost?

The Model 5444B as tested carries a retail price of $2,795.00 USD on Pico‘s online ordering system, which by reference, is about the same price as this tester spent on a 50MHz 2-channel CRT scope with a fraction of the 5444B’s capability 30 years ago. In inflation-adjusted dollars, the price/performance ratio is probably two orders of magnitude better.

So, are pocket size USB oscilloscopes the future? High performance, low price and ease of use are a tough combination to beat, and the PicoScope 5444B has all three.

To learn more, visit the Pico Technology website.


Pico Technology has sponsored this post.  All opinions are mine.  –James Anderton

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