Range & Resolution of Instruments (Edexcel International A Level Physics)
Revision Note
Range & Resolution of Instruments
All instruments have a range and resolution
The range is the highest and lowest value an instrument can measure
The resolution is the smallest increment an instrument can measure
Examples of resolutions for instruments are:
Experimental Instrument | Typical Resolution | Typical Range |
Metre ruler | 1 mm | 0 – 1 m |
Vernier Calipers | 0.1 mm | 0 – 300 mm |
Micrometer Screw Gauge | 0.01 mm | 0 – 25 mm |
Top-pan Balance | 0.01 g | 0 – 1 kg |
Protractor | 1° | 0 – 180° |
Stopwatch | 0.01 s | 0 – 9 hours 59 mins 59.99 seconds |
Thermometer | 1 °C | –10 °C – 110 °C |
Voltmeter | 1 mV – 0.1 V | 0 – 1000 V |
Ammeter | 1 mA – 0.1 A | 0 – 10 A |
Oscilloscope | 1 Hz | 0 – 200 MHz |
These are just examples of ranges and resolutions for these devices
For example, some multimeters may have a bigger or smaller range depending on their model
The resolution of an instrument gives its absolute uncertainty for a digital device
For an analogue device, such as a thermometer, ruler or pan balance, the uncertainty is ± half the resolution
This is because when reading between the millimetre scale the measurement will be rounded up or down by eye from the midpoint at 0.5 mm
Worked Example
Two digital thermometers display a reading in °C.
Thermometer 1: 80.13 °C
Thermometer 2: 42.0 °C
Which thermometer has the better resolution?
Answer:
The resolution is given by the smallest increment that the thermometer can read
For thermometer 1 this is 0.01 °C
For thermometer 2 this is 0.1 °C
Therefore, thermometer 1 has the better resolution
Examiner Tips and Tricks
Exam questions can refer to different instrument with various ranges and resolutions, for example, ammeters with resolution of 0.2 mA instead. Always use the information given in the question, and look carefully at the scales given. Never just assume the resolution of a piece of instrument given in an exam question.
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