Collaborate Disseminate
Those of us who have bought cheap TinyVNA devices for our RF experimentation will be used to the calibration procedure involving short-circuit, 50 Ω, and open terminations, followed by a …read more Continue reading Calibrating a VNA The Proper Way
The smaller ATtiny microcontrollers have a limited number of pins, and therefore rely on an internal 9.6 MHz oscillator rather than an external crystal. This oscillator lacks the accuracy of a crystal so individual chips can vary over a significant tolerance from the nominal figure. Happily the resulting timing inaccuracies …read more
Continue reading Improve ATtiny Timing Accuracy With This Clock Calibrator
When you measure a voltage, how do you know that your measurement is correct? Because your multimeter says so, of course! But how can you trust your multimeter to give the right reading? Calibration of instruments is something we often trust blindly without really thinking about, but it’s not always …read more
Continue reading The Best Voltage And Current Reference This Side Of A Test Lab
It’s tough to find a project these days that doesn’t use an analog-to-digital converter (ADC) or digital-to-analog converter (DAC) for something. Whether these converters come as built-in peripherals on a microcontroller, or as separate devices connected over SPI, I2C, or parallel buses, all these converters share some common attributes, …read more
If you work for a large company, you probably have test equipment that is routinely calibrated. Some companies have their own metrology labs and others send out to an external lab. In a garage lab, you are less likely to do calibrations and — in our experience — that isn’t usually a problem. Still, it is nice to be able to do at least a sanity check on your gear. Also, if you buy old test gear and repair it, it would be nice to be able to check it, as well. [IMSAI guy] built his own little calibration setup, …read more
Sure, we all love fixing stuff, but there’s often a fine line between something that’s worth repairing and something that’s cheaper in the long run to just replace. That line gets blurred, though, when there’s something to be learned from a repair.
This wonky temperature-compensated crystal oscillator is a good example of leaning toward repair just for the opportunity to peek inside. [Kerry Wong] identified it as the problem behind a programmable frequency counter reading significantly low. A TCXO is supposed to output a fixed frequency signal that stays stable over a range of temperatures by using a temperature sensor …read more
Continue reading Drifting Instrument Presents Opportunity to Learn about Crystal Oscillators
An exciting development over the last few years has been the arrival of extremely cheap instrumentation modules easily bought online and usually shipped from China. Some of them have extremely impressive paper specifications for their price, and it was one of these that caught the eye of [Carol Milazzo, KP4MD]. A frequency counter for under $14 on your favourite online retailer, and with a claimed range of 500 MHz. That could be a useful instrument in its own right, and with a range that significantly exceeds the capabilities of much more expensive bench test equipment from not so long ago. …read more
Continue reading Characterizing A Cheap 500MHz Counter Module