The second part of the question triggers another one: "Why would you want to weigh at all if your balance is not calibrated?" Balance or scale calibration is essential to achieve accurate weighing results. Ignoring this important service activity turns measuring into guesswork. In other words, it is negligent to weigh with a non-calibrated balance or scale. The accuracy of balances and scales becomes less reliable over time. This is the result of normal wear and tear caused by regular use and external factors such as mechanical shocks or hazardous environments. This may lead to a rather quick degradation or deterioration over a longer time. Periodically scheduled balance calibration in combination with frequent routine testing greatly enhances the lifetime of your balance or scale and its weighing accuracy.
But what is calibration? In simple terms, calibration is a quantitative comparison. To check the reading of a balance or scale, a reference weight is placed on the pan. The error is defined as the difference between the measured value (the reading) and the true value (the reference weight). The question whether this error is trustworthy or not, will be outlined below. At the end of balance calibration, a certificate is created, which reports on the balance or scale's readings and compares them to a reference value. Applied tolerances result in a Pass/Fail statement.
A calibration certificate reports results at the time the calibration was performed. In many cases the responsible person assumes that the calibration is valid for a year. This leads to the wrong conclusion that a calibration interval of one year is sufficient.
Ideally, calibration intervals are defined following a risk-based methodology, for example what is the probability of something going wrong and how high is the impact? A high impact and high probability corresponds to a high risk, which requires a shorter calibration interval. Otherwise a low impact and a low probability results in a low risk, allowing intervals to be extended.
To forgo calibration is a high-risk strategy. Hidden costs and risks associated with the un-calibrated balance or scale could be much higher than the cost of calibration itself. Using non-calibrated equipment can lead to production problems such as:
Environmental changes can also lead to undetected drift or increasing random errors which degrade performance. Periodically scheduled calibration along with routine testing is the best way to reduce calibration-related risk.