How to Read Beam Scales to Determine Mass

Beam scales are generally used in science labs or medical offices. These scales have three main parts: the pan, the part onto which you place the object you are weighing; the beam, with scales that have two or three beams, although some older and simpler scales will only have one; and the slider, which is moved across the beam to determine the weight of the object on the pan.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Object to weigh

1. Slide all the sliders to the "0" mark on the beams. The beam should point to center, if the scale is calibrated correctly. Place the object onto the pan. The beam should now point upward from center.

2. Slide the largest slider across the beam, notch by notch, until the beam drops. Move the slider back one notch. The beam will most likely go back to its original position. Repeat this procedure for the other beams. On many scales, the last beam will not have notches. Simply move the slider back and forth until the beam points to center.

3. Read the values the sliders are pointing to and add them together. Laboratory triple-beam scales typically use metric mass measurements. The first beam usually measures grams, the second measures tenths of grams and the third measures hundredths of grams. So, if the first beam slider pointed to "7," the second pointed to "3," and the third pointed to "1," then the reading would be 7.31 grams.

Tips & Warnings

• In English units, "pounds" can be used for weight, which is a force, or mass. For most practical purposes, one pound-force equals one pound-mass, so the scale reading is usually accurate for both weight and mass.

References

• Mt. Lebanon H.S. Science Lab Techniques