The Engineering Octopus has launched a keyring with a difference: As well as helping you keep track of your keys, it doubles as a means to quickly test an oscilloscope — hence its name, the Oscilloscope Tester Keyring (OTK).
"All electronic engineers love to show off the fact that they are electronic engineers, and what better way to do that than with a keyring! Not only will the bare electronics be noticed by many, it's also a fully functional oscilloscope tester," The Engineering Octopus founder Max writes. "The OTK generates a pure, analog, sine wave (via a Colpitts oscillator) at approximately 10MHz (+/-2MHz). It has a DC offset, which allows you to test almost all functions of a oscilloscope, and carry it with you everywhere you go!"
"It's battery powered (included!) via a CR2032 watch battery. Or, should the battery go flat on you, it also has a micro USB port so that you can use the oscilloscopes USB port (or a power banks). 'But my oscilloscope has a square wave generator,' I hear you cry? indeed, this is true, but, firstly, it doesn't fit on a keyring! Secondly, you need probes to test with that! Where the OTK really shines is for those of you who love to repair/buy oscilloscopes. More often than not, they're not supplied with probes, and this quick and easy tool can be taken with you to viewings. You simply plug it into the BNC connector, and test it out!"
While Max admits that the OTK is no substitute for true reference testing, and that the sine wave it generates is only "approximately" at the target 10MHz frequency, he's found it particularly useful for a range of troubleshooting tasks including DC, AC, and ground switch testing, CRT intensity, horizontal and vertical positioning, time base issues, volts per division issues, single-shot trigger modes and other triggering issues — "and," he notes, "I'm sure there's plenty more if you're creative!"