CSC Blog Instrument Accuracy? Is it only an illusion?

Regularly I'm asked the question; "How accurate is this moisture balance?"The questioner asks for the answer in terms of percent (%) moisture. When I answer "it depends", I always get the unspoken response, "Why did I ask this stupid idiot?"Absolute MeasurementWhen inquiring about the precision of measurements such as weight or temperature, the responses are clear-cut and tied to the accuracy of the instruments. For instance, 25 grams or 50 degrees with a margin of plus or minus (+/-) 0.1 gram or 1/2 degree.Percent is A Relative Measurement When questioning the accuracy of your percentage reading, the answer can be quite complex. This complexity arises from the fact that percentage (%) is a relative measurement. Take, for example, the outcome of a Loss on Drying (LOD) moisture test, which is heavily influenced by the size of the sample used.To better grasp this concept, consider how the result of an LOD moisture test is derived. It involves subtracting the weight of the sample at the end of the test from its initial weight, and then dividing this difference by the original weight of the sample. This calculation ultimately yields a % moisture reading.Sample SizeThe upcoming analysis will shed light on the impact of both sample size and instrument precision. We will delve into a sample containing 23.5% moisture, examined using an electronic LOD moisture balance with a sensitivity of 0.001 grams and a repeatability of +/- 0.005 grams.Sample Analysis