When you are operating any instrument that deals with high precision measurements, the most leading word to remember is calibration. As we have seen in an earlier article, even the most sophisticated tool has an uncertainty factor built in; and an analytical balance is no exception.
Calibration of an analytical balance is a very leading requirement to ensure that it consistently gives precise readings. As an analogy to calibrating an analytical balance, dream a musician in an orchestra tuning his instrument. The lead violinist sets one true tone and the other musicians tune their instruments accordingly. Similarly a balance needs to be tuned in relation to a true weight. To calibrate a balance, you need to set up a base point (Zero) and produce the instrument's full capacity (Span) weight. This way, you have considered two precise ultimate points, between Zero and Span. It is now possible to fancy all weights in-between with an acceptable degree of precision. There may be applications where the maximum capacity of the balance is unlikely to be ever reached. Some manufacturers offer the facility of calibrating the balance in stages, so that the user can choose the upper limit agreeing to the heaviest substance he is likely to weigh. Why should he do this? Because calibration within a reduced range results in greater accuracy.
To set about calibrating your balance, you will need a weight set that is calibrated to Astm Class 2 and a calibrated weight corresponding to the maximum value. It is recommended that purchase the calibration weight along with the balance. The actual course for calibrating a balance will often depend on the brand and model. Here are a few typical methods.
Ensure that the balance is sufficiently energized by switching it from 30-120 minutes (depending on the model) before you start the procedure. Verify the level of the balance by checking if the level indicator bubble is in the town of the circle. The level can be adjusted by means of the leveling screws at the balance's four corners. Press the On button to briefly turn the balance on. Next, press the tare button to tare the balance with an empty pan. Then the Cal/Menu button on the balance should be pressed and held. Cal (or Calibration) will appear on the display. When the display blinks the value of the calibration weight, the weight should be settled on the pan. Take care not to cope the weight with bare fingers. After a while, the display will read zero and that is when the calibration weight should be removed.
Some balances have an internal motorized auto-calibration feature, which plainly adds to the cost. Moreover, balances with an external certified calibration are beloved by Iso 9000. That is why such balances also allow for external calibration. The benefit of external calibration is more suitable and thrifty to send the cut off calibration mass to a testing facility than to take off the inbuilt internal calibration mechanism and send it out for re-calibration. Moreover, if your preparing owns several of the same analytical balances, you only need one external traceable calibration, in order to comply with Iso mandates.
