Most middle school students must learn to use a triple beam balance scale at some point during their science classes. Often used by physics or chemistry teachers to demonstrate the principle of mass, these devices can be used to weigh any object within their weight limitations. Triple beam balance scales function by balancing an object with three counterweights—attached to the scale—to accurately find the object's weight. Using one of these devices is not difficult.

### Step 1

Calibrate the scale by sliding all three weight poises (the metal brackets that slide along the three beams) to their leftmost positions. Twist the zeroing screw (usually located below the pan in which you place the object to be weighed) until the balance pointer lines up with the fixed zero mark.

### Step 2

Place the object to be weighed on the center of the pan.

### Step 3

Slide the 100-gram poise right one notch at a time. When the indicator drops below the fixed mark, move the poise left one notch.

For instance, if your object weighs 487 grams, the 100-gram indicator would drop below the fixed mark on the fifth notch (500 grams). Move the poise back to the 400-gram notch.

### Step 4

Slide the 10-gram poise right one notch at a time. When the indicator drops below the fixed mark, move the poise left one notch.

In the case above, the 10-gram indicator would drop below the fixed mark on the ninth notch (90 grams). Move the poise back to the 80-gram notch.

### Step 5

Slide the 1-gram poise slowly across the third beam. There are no notches, so keep an eye on the pointer as you slide. Stop sliding when the pointer lines up with the fixed mark.

In the case above, the 1-gram poise will cause the pointer to line up at the fixed mark at 7 grams.

### Step 6

Add the values of all three beams to determine the mass of your object.

In the case of our example, add 400 + 80 + 7, resulting in an object mass of 487 grams.