Weird or what?

I have made a similar mistake in attempting to weigh something with the tight fitting transparent cover still on the weighing platform. It took me a good few minutes to work out what was going wrong - it was only when I turned it over to fit new batteries that the cover fell off.

The unit still worked with the weighing platform cover in place but just gave the wrong results. As I knew the approximate weight of the item I established almost instantly that something was wrong - but not why.

My set of (drug dealer) scales have two transparent covers. One covers the whole unit but the second just the weighing platform leaving access to the buttons.

The idea of the second cover is to remove it and turn it over where it acts as a tray with lips around the edge.

Bingo. That was the problem, The second transparent cover.

In my case I wanted it well out of the way.

I also have a set of drug-dealer scales, they zero themselves when turned on, but they start showing a non-zero reading as soon as you bring something into proximity of the pan. Do they all do that?

no, not seen that happen before

Mine read zero when switched on but doesn't have any proximity problems. The display remains at zero until something is actually placed of the weighing surface.

Mine don't. BTW, a 20p piece is a useful 5.0g. (So is an A4 sheet of

Nope. mine doesnt.

There's a pretty standard chip that's used in all of these devices. It includes a small degree of prescience, which allows it to anticipate the mass of items you are about to place on them. It's easily fooled.

Our new kitchen scales when turned on show zero grammes for about 2 seconds, and then jumps to 2 grammes. Once re-zeroed it seems to behave. Annoying as we didn’t keep the receipt.

Tim