I got hold of a second hand one of these:
https://www.torontosurplus.com/rs-co...lampmeter.html
A HEME 100 clamp meter.
I can't find specs for it online, only a HEME 1010.
I've tried reading a few currents with it (using a brand new battery in it), and it seems to underread a fair bit on DC (0.56A instead of 0.62A) and AC (7.5A instead of 8.5A). It's also susceptible to wires near it - for example if you put the live inside the clamp but the neutral is an inch or so from the outside of the clamp, it reads a bit of that too and gives a higher reading. Are these things supposed to be accurate? Can I adjust it?