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Test Equipment

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Test Equipment Alternatives (Suggested By You!)

test equipment alternatives

A couple of weeks ago, I asked my subscribers for their favorite test equipment alternatives. The reason I asked, was because I recently picked up a Mooshimeter. It is a modern take on the multimeter. However, I will cover that in more detail soon.

While I am fortunate that my bench has the usual equipment like an adjustable power supply, oscilloscope, multimeter, and function generator, I know that not everyone else does. I also had to think back to before I had this equipment, what did I use to troubleshoot my circuits.

Sometimes when working on a project, whether hobby or professional, you just don’t have the tools you need on hand. Or worse, you cannot afford it. So here are some of the responses you all sent me.

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Arduino

Benchmarking Arduino’s digitalWrite() with a Logic Analyzer

digitalWrite with Logic and Arduino Uno

Recently I picked up a device called Logic from Saleae. It’s a 4-channel USB-based logic analyzer. While learning how the simple, but effective, UI works I ran some timing benchmarks on my Arduino Uno. The subject? digitalWrite(). I wanted to know how fastdigitalWrite() could turn on two (or more) pins.

Almost all Arduino users start out with the simple “blink” sketch. Turn pin 13 ON, delay, turn it OFF, and delay again. The heart of this version of “Hello World!” is the digitalWrite() function. Many Arduino users never even think about all of the stuff this single function call hides.

In this post, let’s compare the speed of digitalWrite() to direct port manipulation, using a logic analyzer.

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Reviews

Review of NI’s VirtualBench, All-In-One Instrument

VirtualBench

The first time I saw the VirtualBench from NI, I was amazed by its shear size—or lack of size.  At the time, the unit I had access to an uncalibrated pre-release unit at the Austin TechShop.  So I didn’t think it was fair to do a full review.  Fast forward to today.  Now that I’ve spent a week working with the VirtualBench I have some comments and thoughts.  What follows is a review of this “All-In-One Instrument” that runs $1999 USD.

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Around The Web

DIY Active Differential Probe Project

Active Probe Setup (via xellers)
Active Probe Setup (via xellers)

Back when I worked for an Oscilloscope company, we were pretty proud of our differential probes.  Even the “low-bandwidth” probes were still around 1GHz of bandwidth.

Daniel Kramnik built an active differential probe and looks like he is seeing about 400MHz usable bandwidth.  And really, it looks relatively flat.  Not bad for a DIY effort.  I’m impressed.

Pretty amazing to think about the possibility of building your own (active) scope probes.

Read his full writeup.

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Around The Web

HPDisk – GPIB Disk Emulator

Images from http://www.dalton.ax/hpdisk/
Images from http://www.dalton.ax/hpdisk/

Popular on eBay are old test equipment like Spectrum Analyzers, Oscilloscopes, and Multimeters. HPDisk by Gustafsson Anders creates a virtual GPIB interface that stores data to a SD-Card.This is done by emulating a special HP disk drive, that some HP instruments know how to write to when connected. (As Anders points out, this is not emulating a built-in floppy drive.)

Keep reading if you aren’t familiar with GPIB.

What’s GPIB?

Long before USB became the standard I/O interface in the computing world, bench-top instruments used HPIB. This was the “HP Interface Bus” used by Hewlett-Packard in the early days of their test equipment. It enabled instruments to share data and be automated by “desktop computers”.

Eventually HPIB evolved into GPIB and the IEEE-488 standard was created. Until about 2000, most instruments supported a true GPIB/IEEE488 hardware connector. Slowly that evolved into USB-based virtual connectors (like a virtual serial port).

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