Systematic Errors Systematic errors cause all readings to be above or below the right value.
Systematic errors can happen when the measuring instrument is faulty or has not been set correctly, or when a person takes every measurement the wrong way.
A zero error is a type of systematic error. It happens when you use an instrument that has not been set to zero. This may be because of wear and tear (for example, the ends of a metre stick wearing away) or forgetting to reset an instrument (such as an electronic balance).
15.4
N
40 N 350 N 350 N
Fig. 15.4.2 A worn metre stick
Fig. 15.4.3
Coal 310 N
Coal 310 N
Zeroing an Electronic Balance
Most electronic balances have a button on the front that says ‘zero’ or ‘tare’.
When you turn on the balance, press this button once before you use the balance. This will reset the reading on the balance to zero.
The spring balance on the left should read zero, but because of a systematic error it reads 40 N with nothing attached to the hook. Now every reading will be heavier by 40 N. The actual weight of the bag of coal is 310 N, but the balance reads 350 N
