The Limitations of Measuring Instruments

Imagine you were doing an experiment in which you were required to measure the temperature of a liquid. What should you consider when choosing a thermometer?

Resolution
Do you need to measure to the nearest degree, half a degree or tenth of a degree. The resolution is the smallest possible difference the instrument can detect. A high resolution isn't always the best, especially when there is a high degree of uncertainty in the measurements.

Sensitivity
If a small change in the quantity you are measuring produces a large change in the reading from the instrument (e.g. the needle moves a lot) then it is very sensitive.

Calibration
Calibration is the process of establishing the relationship between a measuring device and the units of measure. You would calibrate a set of scales by putting test masses on and checking that the correct reading is given. Trading standards officers visit shops to do this.

Response time
How long does it take before the meter registers a correct reading?

Stability
How prone is the instrument to random errors?

Zero error
When the quantity is zero then the meter should read zero. If it doesn't then every reading will be out by at least this amount. Zero error is a good example of a systematic error, i.e. one that is due to a bias in the system.