An Absolute Uncertainty Calculator is a tool used in scientific measurements and experiments to determine the range of possible values for a measured quantity.
Imagine you’re measuring the length of a table using a ruler. You might measure it as 150 cm, but due to limitations in the ruler’s markings and your ability to read it precisely, there’s some uncertainty in this measurement.
An absolute uncertainty calculator might determine that the true length could be anywhere between 149.5 cm and 150.5 cm. In this case, we’d say the length is 150 cm ± 0.5 cm, where ±0.5 cm is the absolute uncertainty.
Absolute Uncertainty Calculation Chart
| Measurement | Value | Uncertainty | Result with Uncertainty |
|---|---|---|---|
| Length | 10.2 m | ± 0.1 m | 10.2 m ± 0.1 m |
| Mass | 5.67 kg | ± 0.02 kg | 5.67 kg ± 0.02 kg |
| Time | 3.45 s | ± 0.05 s | 3.45 s ± 0.05 s |
| Temperature | 25.3°C | ± 0.2°C | 25.3°C ± 0.2°C |
| Voltage | 12.0 V | ± 0.1 V | 12.0 V ± 0.1 V |
Absolute Uncertainty Formula
The formula for absolute uncertainty depends on the specific situation, but a common approach is:
Absolute Uncertainty = (Maximum Value - Minimum Value) / 2You measure the width of a door five times and get the following results: 80.2 cm, 80.5 cm, 80.3 cm, 80.1 cm, and 80.4 cm.
Find the maximum value: 80.5 cm
Find the minimum value: 80.1 cm
Apply the formula: (80.5 cm – 80.1 cm) / 2 = 0.2 cm
Therefore, the absolute uncertainty in this measurement is ±0.2 cm, and we’d report the door width as 80.3 cm ± 0.2 cm.
How do I calculate absolute uncertainty?
To calculate absolute uncertainty:
Take multiple measurements of the same quantity.
Identify the highest and lowest measured values.
Calculate the difference between these values.
Divide the difference by 2 to get the absolute uncertainty.
You’re measuring the temperature of a liquid. You take five readings: 22.1°C, 22.3°C, 22.0°C, 22.2°C, and 22.4°C.
- Highest value: 22.4°C
- Lowest value: 22.0°C
- Difference: 22.4°C – 22.0°C = 0.4°C
- Absolute uncertainty: 0.4°C / 2 = 0.2°C
The result would be reported as 22.2°C ± 0.2°C (using the average of all measurements as the central value).
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