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This is one my lesson in my Ultimate Chemistry Course ([ Ссылка ]) which is still under construction.

Analog measurements always demand a little more energy to read them, this is why students much prefer digital instruments. In my experience as an educator, performing an analog measurement is an excellent opportunity to discuss certainty in measurement.



Always remember that for every analog measurement that you get a guess for the last digit. Take the 1st picture below for example. Think about what you are certain of when you read this measurement. You KNOW that the mass is reading somewhere in between 3 and 4 grams. Because there are even smaller divisions, you can even say that you KNOW that the weight is between 3.2 and 3.3 grams. This is where most students stop. They will say 3.2 or 3.3 grams and leave at that. If they say 3.2 grams they would be WRONG! Scientific convention states that the last decimal place in a value is an assumed guess. That means they can guess one more decimal place. Here, I would say that the marker is a little closer to the 0.3 then the 0.2, so I will call this 3.27 grams.



Now, the trickiest part of analog measurements is when the marker is exactly on one line. Take the 2nd example below. Students will be quick to call this 6 grams. If they did this, they would be discounting the precision of the instrument. Some might say, that this is 6.0 grams...and they would be wrong. They are wrong because they are certain of the tenths place digit. The correct measurement here would 6.00g...or 6.01g...or 5.99g.

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