@Martin--it is interesting to think through this switch thing. All handheld DVMs/DMMs have at least one big rotary switch. When we used those in production, they had to be calibrated/certified. There were stickers on them showing the dates, and when they were due back to re-cert. But I don't ever recall anybody checking the meter if they changed the rotary switch. There is some exposure there that you could be doing bad measurements.