Short Answer
Zero error is the error that occurs in a measuring instrument when its pointer or reading does not show zero even though the quantity being measured is actually zero. This means the instrument has a built-in mistake before measurement begins.
Zero error affects the accuracy of all measurements taken using that instrument. To get the correct value, the zero error must be identified and then added or subtracted from the measured reading. Common instruments that show zero error include vernier callipers, screw gauges, and ammeters.
Detailed Explanation :
Zero Error in Measuring Instruments
Zero error is an important concept in measurement and experimental science. Every measuring instrument, whether simple or advanced, must show zero when no quantity is being measured. However, due to wear and tear, manufacturing defects, improper handling, or calibration issues, some instruments do not show zero when they should. This mistake in the initial reading is called zero error.
Understanding zero error is necessary because it directly affects the accuracy and reliability of the measurement. If zero error is not corrected, every reading taken using the instrument will be incorrect and misleading.
Meaning of Zero Error
Zero error occurs when a measuring instrument does not start from zero even when the true value is zero. This means the instrument has a built-in shift in reading. For example:
- A vernier calliper may show 0.02 cm even when the jaws are fully closed.
- A weighing scale may show 200 g without placing anything on it.
- A micrometer screw gauge may show a slight reading even before measurement begins.
In all these cases, the initial or starting point is wrong. Such an error must be corrected before using the instrument.
Why Zero Error Occurs
Zero error can occur due to several reasons:
- Improper handling of the instrument
- Dust or dirt between measuring surfaces
- Wear and tear from long use
- Manufacturing defects
- Inaccurate calibration
- Loose or damaged parts
Because of these factors, the instrument fails to return to its true zero position when not measuring anything.
Types of Zero Error
Zero errors are mainly of two types:
- Positive Zero Error
This occurs when the instrument shows a reading above zero when it should show zero.
Example:
If a vernier calliper reads +0.03 cm when fully closed, it has a positive zero error.
To correct this, the zero error is subtracted from the observed reading.
- Negative Zero Error
This occurs when the instrument shows a reading below zero when it should show zero.
Example:
If a screw gauge reads –0.02 mm when nothing is measured, it has a negative zero error.
To correct this, the zero error is added to the observed reading.
These two types help us understand whether the instrument is reading more or less than it should.
How Zero Error Affects Accuracy
Zero error changes every measurement taken using that instrument. For example:
If an instrument with +0.05 cm zero error is used to measure 5.00 cm, the instrument may show 5.05 cm.
If the error is not corrected, all readings become inaccurate.
Because accuracy is very important in science, engineering, and laboratories, identifying and correcting zero error is an essential part of measurement.
Correcting Zero Error
To correct zero error, follow these steps:
- Check the instrument before measurement — make sure it reads zero when nothing is measured.
- Note the zero error — whether it is positive or negative.
- Apply correction —
- For positive zero error → subtract the error.
- For negative zero error → add the error.
This ensures that the final reading becomes correct.
Examples of Zero Error in Common Instruments
Vernier Callipers
The main scale and vernier scale may not align at zero, causing zero error.
Students often see this error in physics labs.
Screw Gauge
If the pitch scale and circular scale do not align at zero, a zero error is present.
Pointer Instruments (Ammeter or Voltmeter)
If the needle does not rest at zero when no current flows, the instrument has zero error.
Why Zero Error Must Be Removed
Zero error must be corrected because:
- It affects accuracy of all readings
- It leads to wrong calculations
- It affects experiments and results
- It reduces reliability of instruments
- It creates systematic error in every measurement
By correcting zero error, measurements become more reliable, consistent, and scientifically valid.
Conclusion
Zero error is the error that appears in a measuring instrument when it does not show zero even though the actual measurement is zero. It can be positive or negative and must be corrected to ensure accurate readings. Zero error affects every measurement taken with that instrument, so identifying and correcting it is essential in scientific experiments, laboratory work, and engineering measurements. Correcting zero error ensures precision, accuracy, and reliability.