When determining whether a Bombarding A.C. Milliamperes Meter is an RMS Iron-Vane meter or an inexpensive rectified meter, each type of meter is easily identified simply by visually looking at it.

On a True RMS Iron-Vane meter (top picture) the space between the graduations at the lower end of the scale (left side of the scale) are non-linear. In other words, they are not the same distance apart; they are closer together than they are on the rest of the scale.

On a rectified meter (bottom picture) the space between the graduations is linear across the entire scale. In other words, the space between all the graduations is the same, even at the lower end of the scale.

The linear scale characteristic of the inexpensive rectified meter may seem to contradict the accuracy statement that favors the RMS meter because the scale of the rectified meter is more readable at the lower end and therefore more “user friendly” at low readings. However, in this instance the looks are deceiving. With the rectified meter what you see (the reading on the scale) is not what you get (the actual amount of current).