When visiting the doctor's office it is likely that you have noticed the scales used there to measure your weight are very different than most at-home models. This type of scale is referred to as a physician beam scale and is ideal for determining an accurate weight.
Ensure that the scale is calibrated. When the large counter weight and the small sliding weight are both on zero, the rotating beam should come to a stop where it is completely horizontal and the needle on the far right end is in the center of the slot.
Remove your shoes and any heavy clothing such as a jacket before stepping on the scale. This will give you a more accurate reading for your weight.
Determine an estimate for your weight so that you'll know a general place for beginning the measurement. For example, if you know you are around 155 pounds you can start the scale there.
Step onto the scale facing the beam. Slide the large counter weight to a number less than, but closest to your estimated weight. For example if you think you weigh about 155 place the counter weight on 150.
Slide the small weight slowly along the scale. You will feel small notches along the scale where the sliders can rest at each weight increment. Watch the balance beam. Once at the correct weight it should come to a stop completely horizontal with the needle in the center of the slot as it did when the scale was at zero.
Adjust the small weight slowly up or down if the beam did not rest horizontally in a straight line. If the estimate was way off you may also need to adjust the large counter weight.
Determine your actual weight once the beam comes to rest in a straight line horizontally. The large counter weight gives you the first part of the number, such as 150, and the small weight gives you the additional amount. For example if it is set on 6 then your weight would be 156.
If the scale is not calibrated correctly you will need to consult the instruction manual to learn how to accomplish this. Typically a screwdriver or similar item can be used to turn a screw on one side of the beam which will move it up or down and closer to zero as needed.