Why ohm's ranges + lead is black and - lead is red.

Sunday, March 09, 2014

Q. I have the analog meter that comes standard with my course. In lesson 1408 it says that on the ohms ranges, the + lead is the black one and the - lead is the red one. Isn't this backwards? I thought red was always + and black was always -.

A. To make the red lead + and the black lead - on the ohmmeter ranges would require an extra set of contacts on the range selector switch. This would make the meter more expensive than necessary, the extra cost would be reflected in the cost of your course.

The extra contacts would also make the switch more complicated, which would reduce the reliability of the meter. When we chose this meter, we felt that our students would be able to understand this difference. If you wish, you can simply unplug the leads from the meter and swap them around when yolu are using a resistance range. 

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