This article discusses basic theory on the decibel unit and its role in electrical measurements of power, etc. It also describes the construction of an RF power meter which in the past has been difficult to use and expensive to own. With the breakthrough of new ICs in recent years, most of the former problems and expense have been eliminated. This is a simple and inexpensive unit to build, but has the accuracy, resolution, and dynamic range that was only obtainable in lab quality test equipment a decade or so ago. This kind of test equipment is almost mandatory for amateurs, radio frequency work, or test equipment calibration. Also, when built as described, it’s a very professional looking piece of gear that anyone would be proud to display on their test bench.
The oscilloscope is my go-to measurement instrument in every electronics project I work on, helping me debug and fine-tune hardware and software projects. In this article, I’ll show how you can get started with a simple-to-use scope you probably already have. Best of all, it’s free! When you graduate from this simple scope, you can purchase a more powerful scope using the exact same user interface. I think the free scope control software, Waveforms, is the simplest to use, most feature-rich pro-level software of any of the available options. Using a sound card as the hardware interface with Waveforms puts a simple yet powerful scope in your hands for free.
One thing you want to check before you start a long 3D print job is to verify you have enough filament on the spool to complete the print. You don’t want to come back to your printer at the end of a two-day run (as I have!) only to discover that the machine ran out of filament and the top part of the object is missing! This project describes a dedicated “spool scale” that provides a real time readout via an Arduino of just how much material you have left.
A voltage reference is a zener diode-like semiconductor that produces an accurate fixed voltage; often, five or 10 volts. The downside to a voltage reference is that it only generates a single voltage and has limited current output. I decided to design a circuit that could generate any voltage between zero volts and 10 volts in 0.1 volt increments. Here’s how I constructed my variable voltage regulator.
Most frequency counters can tolerate only low levels of RF at their input, but here’s a way to safely measure the frequency of an RF signal of up to 200 watts with your existing frequency counter.
Over the years with different companies I’ve worked for, I always had access to high-end audio THD (Total Harmonic Distortion) analyzers. I found these very useful for design work, debugging, and repair of audio equipment. My present company has no need for them and consequently they aren’t included in their armory of test equipment. Oftentimes, I have need for one but could never afford to own one — not even a used one. I thought this would be a worthwhile project, so this article describes how to construct one.
Sometimes I wonder which of my portable digital voltmeters I can trust — the B&K, Fluke, or Amprobe. Usually, they’re pretty close but it bugs me not knowing whether they are right on the nose. Fortunately, these days, there are a number of very accurate voltage reference circuits that you can build or purchase for a few dollars.