random thoughts of an engineer

 Today's post will be quick one. I got too irritated by all PCB clamps that don't all work all too wall so I decided to make my own! Inspiration came mostly from optical tables we use all around our labs. I decided to make thin, heavy base plate with M3 holes every 10mm and adapters to be able to mount support wherever I want. The design looks like this: quick render of design Before commiting to expensive and long process of getting them milled from steel plate I decided to make sure that it's as useful as I think. For that I 3d printed prototype out of PLA. I wanted to make it out of black PLA but part way through filament ended and I had to quickly switch to orange. This is how it looks assembled: PCB mounted for soldering everything prepared for mounting PCB It make look more complex than usual clamps to use but keep in mind that if board has screws on 10mm raster then spacers can be screwed directly into base plate. Additionally thanks to modular design boards can be m...

 So what this story is about? Qpass is a method of measuring weight of small mass by depositing it on quartz resonator and measuring changes in electrical properties. Most common are frequency and Q factor changes. Of course because it's sensitive method and requires disposable quartz resonators it's used mostly for very sensitive measurements, hence detected deviation values are very small too, often at the order of sub ppm. Typical solutions Most modern commercial solutions use frequency scanning, building frequency or frequency and phase response and searching for peaks and 3dB width. There're few problems with that solution. For once it requires very dense scanning to make sure you find basic mode and not spurious ones. Phase measurements help in finding "missed" resonances but requires more complex analog frontend. Big upside of this method is that one finds interesting mode they can just scan very small range to track Q and resonant frequency. Another someti...