I recall some years later a young graduate engineer coming into my office with a rather involved circuit consisting of 30/40 TTL ICs and complaining that he'd double checked the circuit and it still didn't work. I took one look at his device then went to the draws of capacitors and handed him a handful of 0.1uF ceramic caps and told him to put them between the ICs' PS rail pins to ground which he did and to his amazement the circuit worked immediately.

He stood in amazement that I should have such insight so as to fix the problem at first glance.

How such critical knowledge can get lost in university training these days just amazes me.

> This switching causes ripples in the voltage line,

But what is on the scope is not that ripple:

> Take another look at the pictures of the ripples above and notice the “M: 20ns” in the top left corner. This signifies that each vertical dotted line is 20ns apart, so the ripple you see has a frequency of something like 50MHz.

The switching regulator does not operate anywhere near 50 Mhz. Those voltage fluctuations are caused by the magnetometer itself: its own internal switching causing rapid current demand fluctuations. Or, possibly, it could be some other nearby device, in which case that device needs the decoupler (also).

This is why the decoupling capacitor addresses the problem. The purpose of the decoupling capacitor isn't to filter power supply ripple, but to provide a local, low-impedance current source that can swallow changes in current demand. That's why it's placed close to the device. It not only ensures that the device has smooth power, but also reduces the noise that it generates, protecting other devices.

Unless you have a 50MHz buck converter (which would be very exotic --- the fastest common ones are around 1/10th that), that looks more like something may be inadvertently oscillating and/or you're picking up strong RF noise from possibly something in...

https://en.wikipedia.org/wiki/6-meter_band#Radio_control_hob...

And "leared" -- the (unintentional?) pun made me click.

I got myself one earlier this year and it does what it says on the tin. It can also be controlled from a computer via USB serial connection using a text based protocol (albeit poorly documented and a bit buggy). I used some python scripts to program the signal generator and then capture some measurements from the scope to check the frequency responses of some analog electronics circuits for guitar.

There is a small community around, there are a few repos on GitHub for using them and also this very long eevblog thred.

https://www.eevblog.com/forum/testgear/owon-hds-200-handheld...

- Test the converter at various points of load (when prototiping keep some 0ohm resistor/jumper for attaching a resistor load or electronic load).

- When you have to measure things, look around app notes/white papers of manufacturers, you will usually find practical actionable info and some examples. Doing proper measurements is really a discipline of its own, but for low frequency you can get far with the basics of craftsman/rule of thumb engineering. [0] [1]

For example the author here in the videos is mostly measuring the inductance loop between the positive of the rail and wherever ground is (we cannot even see where the osc negative is??) and how this particular loop responds to a cap, not the real bus.

[0] https://www.analog.com/en/resources/app-notes/an-1144.html

[1] https://www.richtek.com/Design%20Support/Technical%20Documen...

You could also try just sticking a 100n and 10n across the smps output too.

Another lesson waiting in the wings from mounting a magnetometer in plane and right next to four BLCD motors, lmao.