| This is for beginners and very much by a beginner. It's meant to try to cover hobbyist needs, and as a starting point to find out which may be the relevant details for you, not for definitive information.
Some basics and reference:
Volts, amps, energy, power · Ground · batteries · resistors · changing voltage · transistors · fuses · diodes · varistors · capacitors · inductors · transformers · baluns · amplifier notes · frequency generation · skin effect
And some more applied stuff:
IO: IO and wired communication · localish communication ·
wireless (ISM RF, GSM, RFID, more) · 802.11 (WiFi) · 802.15 (including zigbee)
Sensors: General sensor notes, voltage and current sensing ·
Knobs and dials ·
Pressure sensing ·
Temperature sensing ·
humidity sensing ·
Light sensing ·
Movement sensing ·
Capacitive sensing ·
Touch screen notes
Actuators: General actuator notes, circuit protection ·
Motors and servos ·
Some stuff I've messed with: Avrusb500v2 ·
Hilo GPRS ·
Bluetooth serial ·
basic audio hacks ·
amps and speakers ·
device voltage and impedance, audio and otherwise ·
Less sorted: Common terms, useful basics, soldering ·
Microcontroller and computer platforms ·
Arduino and AVR notes ·
ESP series notes ·
Electronics notes/Phase Locked Loop notes ·
mounts, chip carriers, packages, connectors ·
signal reflection ·
pulse modulation ·
electricity and humans ·
See also Category:Electronics.
Measure force in one or more directions.
And, since gravity is a force in a fixed direction, sense direction (as long as not saturated by e.g. being spun very fast)
While small, convenient, and cheap, they are neither the most sensitive or the lowest-noise.
As such, they are mostly useful for stronger motion, and most are specced for at least 1g.
Now typically MEMS designs: microelectromechanical - a tiny weight in a chip.
Variant naming comes largely from sensitivity (often in units of Volts/(meter/second)).
From geophone (relatively local)
to local geologic seismographs
to teleseismographs (world-scale) are factors of (very) roughly ten.
A geopheone is essentially a physical oscillator tuned to a specific frequency, and a voice coil to sense the movement.
(choices on the order of 5Hz, 10Hz, 15Hz, with peak response there and some response a factor ten higher(verify). Lower than 1Hz is not practical.)
You can cheap variants for perhaps USD/EUR20, and more modern ones for perhaps three times that.
Hobbyists can get a decent signal quickly by connecting them direct to a differential ADC.
More serious uses would build an in-amp circuit, probably with bandpass.
DIY note: A torn woofer can be made into a geophone by adding a weight on a spring (and solid legs).
See e.g. https://zeidigital.wordpress.com/2015/08/14/base-for-earthquake-detector-geophone/
Potentially designed to detect as low as hundredths of a Hz