What's inside a digital scale & how does it work

Support me on Patreon and get early videos:

Today, let's open a cheap digital pocket scale to see what's inside and how does it work. This one goes up to 500g with 0.01g resolution. It seems to contain a load cell with 4 strain gauges set up in a Wheatstone bridge configuration.

[ammowalk]

Hiya, just wanted to let you know, you're one of the best educaters I've ever encountered. Thank you kindly

[tearex]

I get the notification for this video 4 days after buying this exact scale. Perfect.

[walsayer]

important tip when putting back screws in plastic components. 13:32

[BRUXXUS]

Wow! I didn't expect the traces on the sensors to be visible. It's amazing to me that just bending those a tiny bit causes detectable voltage change. I mean, it's very tiny voltage change, but more than I expected. Super cool!

[misium]

Very informative. The accent is a bonus.

[johnwelbourn]

Not sure how I managed to miss this video first time around DGW, but it's amazing. Describing a tear down video as spellbinding is a bit ott, but this one is close. Incredible.

[eccentric-j]

Thanks! We use one daily to weigh the food we make for our cats, the LED went out and I opened it up, and decided to make it my first electronics project soldering a new LED in there. After reassembly the new LED works (though it is more like a spotlight than an even rectangle of light), however, the scale would behave oddly. Anyway, your breakdown really helped me mount it correctly and now its behaving much more like it is supposed to. Thanks for making this video, it was very helpful!

[keithking]

i heard guys explain these before using basically a resistor, but never fully explained... the Wheatstone configuration makes perfect sense to get a voltage reading of. Thank you for this little bit of knowledge...

[scottgilson]

Great description of how a scale and bridge work. Thanks!👍👍

[dambirambi]

This guy is really funny and a good teacher as well

[algotpihl]

My scale was broken and this video helped me fix it. Thank you 🙏🏼

[frogz]

scales like this are used for postage and marijuana(i would LOVE to hear you pronounce this word) and are 1 of the only reasons americans know how many grams in an oz

[georgeiceman]

I have one exactly like this. Thanks for the teardown. And thanks to you, now i know whats inside of it and how it works.

[aicisha]

Thank you for this teardown and explanation. I did not know how a digital scale works. I'm thinking to support you on patreon, you really deserve it!

[rtos]

Very sensitive measurement needed; remarkable it so cheap.

[Anymouse]

Information about battery life and behavior with dead batteries:
Current when OFF: 0.4 uA (virtually indefinite shelf life - no need to take out batteries)
It gives Low battery warning (refusing to work) bellow 2.5 V so it will use up only around 50% of capacity of normal primary cells and maybe 10% (!) of NiMh rechargeables at best.
Current when ON, without backlight: 3.5 mA (ca. 140 hours of continuous use, assuming using up 50% of an AAA capacity)
Current when ON, with backlight ON: 14 mA when running from 3.2 V (fresh batteries), 7 mA @ 2.8 V and 3.5 mA @ 2.5 V (backlight goes very weak). (hard to guess - few tens of hours, maybe???)
The low battery warning seems to be reliable and the scale doesn't read nonsense with low batteries.

[DB-]

Surprisingly decent scale weight for its price. I have 200 g model and it works great so far even with rechargeable NiMH cells :)

[d-riuz]

Excellent video as always. Glad to see you upload videos more often :)
Also nice to see you upload videos in 1080p

[Taha-df]

thanks for the information you shared especially the one about screw

[snaj]

you can probably put a 500g weight then compansate it. When you remove the weight it will say -500 after that you can measure up to 1kg in teory.