mom31257 Posted September 12, 2013 Share Posted September 12, 2013 If I use a digital scale that does not show any decimal places in the reading, should I consider that an exact measurement? Should I list the measurement to the 10th place with a zero? For example, I weighed a large steel nut at 30 grams. Do I list the measurement as 30 or 30.0? I posted this in the Chemistry social group, but I need to know this morning and don't know if anyone will see it or not. Thanks! Quote Link to comment Share on other sites More sharing options...
Brenda in MA Posted September 12, 2013 Share Posted September 12, 2013 Amy, You cannot list any more significant figures than what the scale displays. Since the scale is showing you 30 grams, that means that the actual weight (assuming the scale is calibrated correctly) is between 29.5 g and 30.4 g, so you cannot list the weight as 30.0 grams (which would mean that the actual weight is between 29.95 and 30.04 g). You should list the weight as 30 grams. Brenda Quote Link to comment Share on other sites More sharing options...
mom31257 Posted September 12, 2013 Author Share Posted September 12, 2013 Thanks, Brenda. I kept reading things about going one more decimal place than the instrument measures when you are using something you have to estimate such as a ruler or thermometer, so I wasn't sure if that applied to electronic equipment or not. Quote Link to comment Share on other sites More sharing options...
Brenda in MA Posted September 12, 2013 Share Posted September 12, 2013 Yeah, that's right with something like a ruler where you can see how much past one line the measurement is, you can sometimes put one more decimal place, like you could probably estimate pretty well whether a reading was 30, 30.5, or 31, but going more "fine" than 0.5 is probably not a good idea in that case. However, with a digital readout that shows 30, you have no way of knowing how close you are to 29.5 or to 30.4, so just putting the number as 30 is the best way to go. Brenda Quote Link to comment Share on other sites More sharing options...
Julie of KY Posted September 12, 2013 Share Posted September 12, 2013 As soon as you record 30.0, you are saying you have three significant figures and that your measurement is somewhere between 29.95 and 30.04. Quote Link to comment Share on other sites More sharing options...
AngieW in Texas Posted September 12, 2013 Share Posted September 12, 2013 Technically, you should record the answer as 3.0 x 101 g or as .030 kg to show that you have two significant digits. If you just record the answer as 30 g, the number of significant digits is ambiguous. Quote Link to comment Share on other sites More sharing options...
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