Materials which in some cases do not fit our purpose. Ammeters are connected to negative (otherwise it is the death of devices, like mine !!). And have a set with two ammeters can in no way be used on multiple assemblies interconnected (by the negative). If voltmeters pose no question, ammeters can be used only on a single mounting tension, or on the English editing (old cars, for example) where the positive is grounded. Unable to make a mounting current measurements of a hard drive in France !! When questioned, the seller has no ammeter connected to positive. Damage (and for me, 2 dead appliances, due to incorrect reading of the Amazon page). So I can advise THAT voltmeters.
