How to select a laboratory balance?

1. Weight Capacity of the Analytical Weighing Balance

You’ll need to select a balance that displays sample weight to the resolution desired. This is described as readout. Readout can be to several decimal places presented in grams or milligrams.

Select a balance with a weighing capacity in excess of the samples you plan to weigh. Some balances also specify the minimum load that can be placed on the weighing plate.

2. Analaytical Balance Weighing Errors

Balance errors are expressed several ways including: linearity and repeatability. Linearity describes the maximum difference between the true weight of the sample over its weighing range and the deviation of readout from that weight.   If you draw a plot of the real sample weight vs. the weight displayed, for a perfect balance this plot would be a straight line.  But nothing is perfect. Laboratory balance specification tables present linearity as a plus/minus (±) figure which represents the maximum ± deviation of the curve from the straight line. For ABT balances with a 10 mg minimum sample size linearity is ±0.2 mg or ±0.3 mg depending on balance capacity; for the ABT balance with a 1 mg minimum load and 101 g capacity linearity is ±0.15 mg.

Repeatability (designated by some manufacturers as reproducibility) is the ability of a balance to display the same result when an object is repeatedly weighed under the same conditions.  Repeatability is usually the standard deviation of 10 consecutive measurements of a calibrated test weight. In the 10 mg minimum load balances discussed here repeatability is 0.1 mg, and for the 1 mg minimum load balance it is 0.05 mg.

Analytical balance accuracy is highly dependent on where the instrument is placed and how it is maintained.  We direct your attention to our post on setting up and maintaining your balance to avoid weighing errors and to insure long term reliable performance.  Again we invite you to contact our experts for advice and suggestions on choosing the correct balance for your weighing requirements.

YK Scientific Instrument is a professional manufacturer and exporter of Laboratory Balances.

Should you have any enquiry, please contact us: sales@yk-instrument.com