Put on the safety glasses and rubber gloves to protect your face and hands.
Plug the balance into a power outlet.
Turn all four control knobs to "0." The zero-adjustment knob is in the top-right corner of the balance, the digital counter knob is below it on the right side of the balance, the 1 to 9 gram weight control knob is on the left side and the 10 to 150 gram weight control knob is below it on the left side.
Pull out the bolt on the arrestment lever, located in the bottom-middle of the balance. Turn the lever all the way to the left so that it sits in the "1" position.
Check the zero-adjustment knob to make sure it is set to "0." Turn the arrestment lever so that it sits in its center "0" position.
Put the sample, contained within either its beaker or Petri dish, inside the balance's center pan. Turn the arrestment lever all the way to the right, so that it sits in its weighing "W" position.
Turn the weight-control knobs to determine the pre-weight of the sample in the balance's right-side display. For example, if the numbers displayed are '121" and "120" inside the center of the display, then turn the knobs until "120" is shown on the right side of the display.
Turn the arrestment lever all the way to the right to put it in its "1" position. The scale will now set itself to determine the precise weight of the sample.
Turn the digital-counter knob counter-clockwise until the line closest to the index fork next to the "g" symbol is centered inside it. This will give the exact weight measurement.
Write down the entire result with pencil and paper. If the numbers displayed before the comma are "120," and the numbers shown after the comma are "8754," then the weight of the sample is 120.8754 grams.
Set the arrestment lever back to its middle "0" position and turn all four knobs to "0" to finish.