Working as a Physicist: Measurements

Measurement process: A structured approach where a physicist first identifies what needs to be measured, then chooses an appropriate instrument before finally recording the measurement.
Physical quantities: These are properties or characteristics of matter that can be measured, such as length, time, mass, and electric current.
Units of measurement: All physical quantities possess units. The SI units (International System of Units) are globally recognised and accepted.

Choosing the right instrument: Instruments should be chosen based on accuracy, precision, range, and resolution requirements. Examples of common instruments include rulers, stopwatches, and ammeters.
Calibration: Physicists must ensure instruments are accurately adjusted to measure quantities. Instruments can drift over time due to wear and tear, temperature changes or other factors affecting their accuracy.
Resolution: This refers to the smallest change in quantity that an instrument can detect.
Techniques: Different techniques might be required for different measurements. For example, a vernier caliper might be used for more accurate length measurements while an oscilloscope might be used to measure voltage changes over time.

Random errors: These are unpredictable fluctuations in measured values around the true value due to limitation in precision of the instrument or observer. Random errors can be reduced by taking a larger number of readings and finding the average.
Systematic errors: These errors occur in a predictable manner and are often due to faults in measurement instruments, or human error such as misreading a scale. Systematic errors cannot be reduced by taking more readings, they can only be eliminated by improving the measurement process.
Absolute and relative errors: Absolute error is the magnitude of the difference between the exact value and the approximation. Relative error is the absolute error expressed as a fraction of the true value.
Accuracy and precision: Accuracy is how close the measurement is to the actual value, while precision is how consistent the measurements are with each other.
Error bars: Used in graphs to show the range of uncertainty for each data point.

Tabulation: A systematic way of recording and organising data for easy interpretation.
Graphical methods: Useful for visualising relationships between different physical quantities.
Statistical analysis: Allows physicists to make inferences from the data collected, such as establishing relationships or trends.
Significant figures: Recorded measurements should only include those digits that are reliable and meaningful. The rules of significant figures help physicists to report measurements accurately.

Integrity: Physicists must ensure the accuracy of their measurements and should not manipulate data to fit preconceived theories or hypotheses.
Industry standards and regulations: Where measurements relate to safety, environmental, or other regulatory standards, these must strictly be adhered to.
Responsible use of resources: Physicists should consider the environmental and cost implications of their measurement processes and strive for efficiency and sustainability.