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apoorvk
can someone explain me how do errors in the vernier scale affects its reading? suppose you have a pair of vernier callipers, whose vernier slide won't jam into the ends properly (kinda zero error). so what do we do to correct our reading? Also can you compare with what happens in a screw gauge?
In a vernier caliper, you can either have a positive zero error or a negative zero error if the zero of the main scale does not coincide with the zero of the vernier scale. If the zero mark is slightly on the right side of the zero on the vernier we have a positive zero error. If it is on the left, then a negative zero error. To get the correct reading, the poistive zero error is subtracted from the final reading and the negative Z.E is added. For a micrometer screw gauge, if the zero on the main scale is not inline with the zero on the circular scale, then we have a zero error. If the zero mark is below the main scale line, then we have a positive zero error. If it is above the main scale (datum line), then we have a negative zero error.Again, the positive error is subtracted and negative is added to the final reading to get the correct reading.
Thanks, but how do we account for the errors in case of the vernier callipers. because we also have to match the vernier and man scale "lines" for finding the reading of the last digit in the measurement?
yes, before taking a reading with a vernier caliper , close the instrument and check the zeros of the main and vernier scale, if they coincide perfectly. If not, then you record the reading the scale is giving and add or subtract it from your final reading Similarly, check for the datum line coinciding with the zero of the circular scale in the micrometer.