Answer :
Final answer:
In a dial indicator, the second smaller needle represents the coarse reading of the total number of revolutions that the larger needle has completed. It essentially keeps track of the number of complete rounds made by the primary needle.
Explanation:
In the context of dial indicators, a second smaller needle typically represents the coarse reading of the total number of revolutions that the larger needle has completed. Similar to an analog meter, the primary (larger) needle swivels on a scale to give precise numeric values, while the secondary (smaller) needle, often called the revolution counter, helps to count the number of total rounds or revolutions made by the primary needle. This allows the user to read both fine measurements (from the primary needle) and coarse measurements (from the second, smaller needle).
For instance, if you consider a dial indicator with each revolution representing 1mm on the larger needle, the smaller needle will increment by 1 for every complete revolution, thereby reading the measure in millimeters(1 revolution = 1mm).
Accuracy is paramount in measurements, hence one must always ensure to read the correct value to avoid errors, bearing in mind the absolute and relative precision of the device.
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