http://www.ck12.org Chapter 3. Measurement
FIGURE 3.4
Here we see three darts thrown at four
different targets. Accurate shots would be
those that were close to the bull’s-eye (the
inner circle). Precision would be the shots
that were close to one another.Calibration
When using measuring devices, we often use a technique calledcalibrationto increase the accuracy of our measure-
ments. Calibration is a method of setting or correcting a measuring device by matching it to known measurement
standards. To better understand calibration, we will look at the example of calibrating a thermometer. All ther-
mometers are slightly different in their temperature readings. One way to calibrate a thermometer is by using the
freezing point and boiling point of water (Figure3.5). If we know that water freezes at 0°C and boils at 100°C,
we can calibrate our thermometer by measuring the temperature of ice water and of boiling water. We place the
thermometer in ice water and wait for the thermometer liquid to reach a stable height, then place a mark at this
height which represents 0°C. Then we place the thermometer in boiling water, and after waiting for the thermometer
liquid to reach a stable height, we place a mark at this height which represents 100°C. We can then place 100 equally
spaced divisions between our 0 and 100°C marks to each represent 1°C. Our thermometer has now been calibrated
using the known values for the freezing point and boiling point of water, and can be used to measure temperatures
of objects between 0 and 100°C.
FIGURE 3.5
A thermometer can be calibrated by mea-
suring the freezing point (0°C) and the
boiling point (100°C) of water. One hun-
dred equally spaced divisions can then be
made between 0 and 100°C.Calibration is used to standardize a variety of measuring devices, including meter sticks, graduated cylinders, scales,
and thermometers. It is a good idea to calibrate any measuring equipment you use in an experiment to make sure the
data you are collecting is measured as accurately as possible.