From the BBC about Fukushima:
The Tokyo Electric Power Company (Tepco) had originally said the radiation emitted by the leaking water was around 100 millisieverts an hour.
However, the company said the equipment used to make that recording could only read measurements of up to 100 millisieverts.
The new recording, using a more sensitive device, showed a level of 1,800 millisieverts an hour.
Okay, hands up everybody who pegs the needle in a gauge and says "eh, it's probably not more than the peg". I thought so.