Measurement Material – To achieve a certain goal in physics, we usually make observations accompanied by measurements. Observation of a symptom is generally incomplete if there is no data obtained from the measurement results. Lord Kelvin, a physicist said, if we could measure what we are talking about and express it with numbers, means that we know what we are talking about.

What do you do when you take measurements? For example, you measure the length of a study table using spans, and find that the length of the table is seven spans. In the measurement above you have taken the span as a unit of length. In fact, in everyday life, we often take measurements of certain quantities using predetermined measuring instruments. For example, we use a ruler to measure length. Measurement is actually a process of comparing the value of an unknown quantity with a predetermined standard value.


Basic Measuring Tool

Basic Quantity of Ruler Length Measuring Tool Calipers
Basic Quantity of Ruler Length Measuring Tool Calipers
Basic Quantity of Ruler Length Measuring Tool Calipers
Basic Quantity of Ruler Length Measuring Tool Calipers
Basic Quantity of Ruler Length Measuring Tool Calipers
Basic Quantity of Ruler Length Measuring Tool Calipers
Basic Quantity of Ruler Length Measuring Tool Calipers
Basic Quantity of Ruler Length Measuring Tool Calipers

* The amount of substance is not measured directly like you measure length with a ruler. To determine the amount of a substance, first measure the mass of the substance. You can learn more in the field of Chemistry studies.

Ruler: to measure an object’s length has an accuracy limit of 0.5 mm.

Caliper: to measure an object’s length has an accuracy limit of 0.1 mm.

Micrometer: to measure the length of an object has an accuracy limit of 0.01 mm.

Balance: to measure the mass of an object.

Stop Watch: to measure time has an accuracy limit of 0.01 seconds.

Thermometer: to measure temperature.

Ammeter: to measure the electric current (multimeter)

Derivative Quantity Measurement Tool

  1. Speedometer: to measure speed
  2. Dynamometer: to measure the magnitude of the force.
  3. Hygrometer: to measure the humidity of the air.
  4. Ohm meter: to measure resistance (resistance) electricity
  5. Volt meter: to measure electric voltage.
  6. Ohm meters and ordinary voltmeters and ammeters use a multimeter.
  7. Barometer: to measure the outside air pressure.
  8. Hydrometer: to measure the density of the solution.
  9. Manometer: to measure closed air pressure.
  10. Calorimeter: to measure the specific heat of a substance.

Terms in Measurement

Accuracy is a measure that expresses the degree of approximation of the measured value to the true value of x0.

Sensitivity is the minimum size that can still be recognized by the measuring instrument/instrument

Accuracy (accuracy) is a measure of the ability to obtain the same measurement results. By assigning a certain value to a physical quantity, accuracy is a measure that shows the difference in measurement results on repeated measurements.

Accuracy aka Measurement Accuracy

Accurate measurement is an important part of physics, however, no measurement is absolutely precise. There is uncertainty associated with each measurement. Uncertainty arises from different sources. Among the most important, apart from errors, are the limitations of the accuracy of each measuring device and the inability to read a measuring instrument beyond the smallest part indicated. For example, if you use a centimeter ruler to measure the width of a board, the results can be confirmed to be accurate to 0.1 cm, which is the smallest part of the ruler. The reason is that it is difficult to determine a value between the smallest dividing lines, and the ruler itself may not be constructed or calibrated to greater precision than this.

When stating the results of a measurement, it is also important to state the accuracy or approximate uncertainty of the measurement. For example, the result of measuring the width of the blackboard: 5.2 plus minus 0.1 cm. The Plus minus 0.1 cm (approximately 0.1 cm) result represents an estimate of the uncertainty in the measurement so that the actual width is most likely to be between 5.1 and 5.3.

The uncertainty percentage is the ratio between the uncertainty and the measured value, multiplied by 100%. For example, if the measurement result is 5.2 cm and the uncertainty is 0.1 cm, then the percentage of uncertainty is: (0.1 / 5.2) x 100% = 2%.

Often, the uncertainty in a measured value is not stated explicitly. In such cases, the uncertainty is usually assumed to be one or two units (or even three) of the last number given. For example, if the length of an object is expressed as 5.2 cm, the uncertainty is assumed to be 0.1 cm (or perhaps 0.2 cm). In this case, it is important not to write 5.20 cm, because that represents an uncertainty of 0.01 cm; assume that the length of the object may be between 5.19 and 5.21 cm, while in fact you would expect the value to be between 5.1 and 5.3 cm.

Absolute and Relative Uncertainty

Measurement results are always reported as x = x plus minus delta x where delta x is the instrument’s smallest half scale (single measurement) or is the standard deviation of the sample mean value (repeated measurement). Delta x is calledabsolute uncertainty. Absolute uncertainty relates to the accuracy of the measurement, where the smaller the absolute uncertainty is achieved, the more precise the measurement. For example, measuring length with a micrometer screw, L = (4,900 0.005) cm. The value of 0.005 cm is the absolute uncertainty obtained from the smallest half of the micrometer scale and 4.9 is an exact number.