Measurement is the process of determining the size, amount, or degree of something. In science and engineering, measurements are used to gather data and make calculations.
Measurements are usually expressed in units. Units are a way to indicate the amount of a quantity.
Measuring instruments are tools that are used to measure physical quantities such as length, mass, time, and temperature.
The International System of Units (SI) is the standard system of units used for measurement in science and technology. It is based on seven base units:
| Physical Quantities | Symbol | Units | Symbol of Unit |
|---|---|---|---|
| Length | l | Metre | m |
| Mass | m | Kilogram | kg |
| Time | t | Second | s |
| Electric Current | I | Ampere | A |
| Temperature | T | Kelvin | K |
| Luminous Intensity | Iv | Candela | cd |
| Amount of Substance | n | Mole | mol |
| Physical Quantities | Symbol | Units | Symbol of Unit |
|---|---|---|---|
| Speed | v | Metre/Second | m/s |
| Acceleration | a | Metre/Second2 | m/s2 |
| Volume | V | Cubic Metre | m3 |
| Force | F | Newton | N (kg m/s2) |
| Pressure | P | Pascal | Pa (N/m2) |
| Work | W | Joule | J (N.m) |
| Charge | Q | Coulomb | C (A.s) |
The metre is defined as the length of the path travelled by light in a vacuum during a time interval of 1/299,792,458 of a second.
Kilogram:
The standard for the kilogram is a cylinder made of platinum-iridium, about 39 millimetres wide and tall.
Second:
A second is the duration of 9,192,631,770 periods of the radiation of the caesium-133 atom.
Prefixes:
A prefix is a word part added to the beginning of a measurement unit to indicate a multiple or a fraction of that unit.
A few of them are:
Kilo:
“Kilo-” means 1,000 times, so a kilometre (km) is 1,000 metres (m).
Centi:
“Centi-” means 1/100th, so a centimetre (cm) is 1/100th of a metre.
| Prefix | Symbol | Multiple |
|---|---|---|
| Exa | E | 1018 |
| Peta | P | 1015 |
| Tera | T | 1012 |
| Giga | G | 109 |
| Mega | M | 106 |
| Kilo | k | 103 |
| Hecto | h | 102 |
| Deca | da | 101 |
| Deci | d | 10-1 |
| Centi | c | 10-2 |
| Milli | m | 10-3 |
| Micro | μ | 10-6 |
| Nano | n | 10-9 |
| Pico | p | 10-12 |
| Femto | f | 10-15 |
| Atto | a | 10-18 |
A Kilo for weight is 1000 grams, while a kilo for bytes is 1024 bits.
Length is measured by multiple instruments; a few important ones are:
A metre rule is a measuring tool used to measure length or distance. It is a long, flat piece of metal or plastic with markings on it that indicate different measurements in metres.
Working
To use a metre rule, simply line up the starting point of the measurement with the “0” mark on the ruler, and read the measurement at the end point. It’s important to make sure the ruler is straight and not bent when taking measurements.
A Vernier Caliper is a measuring tool that is used to measure the distance between two points with great precision.
Working
It consists of two main parts: a main scale and a vernier scale. The main scale is fixed and has markings that indicate the measurement in millimetres or inches. The vernier scale is a sliding scale that is used to measure smaller increments of measurement that are not visible on the main scale. By reading the main scale and the vernier scale together, a precise measurement can be taken.
A micrometre screw gauge is a precision measuring instrument used to measure small distances or thicknesses.
Working
It consists of a long, thin metal rod with a screw thread on one end, and a handle on the other. The micrometre screw gauge is used by rotating the handle to move the rod towards or away from the object being measured. The distance between the object and the end of the rod can be read on a scale, which is usually marked in increments of 0.01mm.
Mass is measured by multiple instruments; a few important ones are:
A physical balance is a device used to measure the weight or mass of an object. It works by comparing the unknown weight to a known weight, called a standard weight.
Working
It consists of a beam with a pivot point in the middle and two pans hanging from either side. The unknown weight is placed on one pan, and standard weights are added to the other pan until the beam is level and the two pans are in balance.
An electronic balance is a type of scale that uses electronic sensors to measure the weight of an object. It typically displays the weight on a digital screen and can be used to weigh items with a high level of accuracy.
Time is measured by multiple instruments; a few important ones are:
A stopwatch is a device used to measure the time that has passed. It can be started and stopped at any point, allowing the user to measure the duration of an event or activity. They typically have a digital or analogue display that shows the time in seconds or minutes. These stopwatches are further divided into two other types:
A mechanical clock can measure time for up to 0.1 seconds. It starts up when its knob is pressed and stops when the knob is pressed again.
A digital stopwatch can measure time up to 0.01 seconds. It starts when a button on it is pressed and stops when that button is pressed again. It further has an option that registers a “lap“.
The human reaction is slower than any mechanical process, which happens almost instantly. This means that all machines that require humans to stop or start will have a margin for error. A better replacement for devices like these would be “light gates” because light travels almost instantly.