<P> The accuracy of micrometers is checked by using them to measure gauge blocks , rods , or similar standards whose lengths are precisely and accurately known . If the gauge block is known to be 0.7500 '' ± . 00005 '' ( `` seven - fifty plus or minus fifty millionths '' , that is , `` seven hundred fifty thou plus or minus half a tenth '' ) , then the micrometer should measure it as 0.7500 `` . If the micrometer measures 0.7503 '' , then it is out of calibration . Cleanliness and low ( but consistent ) torque are especially important when calibrating -- each tenth ( that is , ten - thousandth of an inch ) , or hundredth of a millimeter , `` counts '' ; each is important . A mere spec of dirt , or a mere bit too much squeeze , obscure the truth of whether the instrument is able to read correctly . The solution is simply conscientiousness -- cleaning , patience , due care and attention , and repeated measurements ( good repeatability assures the calibrator that his / her technique is working correctly ) . </P>
<P> The accuracy of micrometers is checked by using them to measure gauge blocks , rods , or similar standards whose lengths are precisely and accurately known . If the gauge block is known to be 0.7500 '' ± . 00005 '' ( `` seven - fifty plus or minus fifty millionths '' , that is , `` seven hundred fifty thou plus or minus half a tenth '' ) , then the micrometer should measure it as 0.7500 `` . If the micrometer measures 0.7503 '' , then it is out of calibration . Cleanliness and low ( but consistent ) torque are especially important when calibrating -- each tenth ( that is , ten - thousandth of an inch ) , or hundredth of a millimeter , `` counts '' ; each is important . A mere spec of dirt , or a mere bit too much squeeze , obscure the truth of whether the instrument is able to read correctly . The solution is simply conscientiousness -- cleaning , patience , due care and attention , and repeated measurements ( good repeatability assures the calibrator that his / her technique is working correctly ) . </P>
the least count of a mere scale is
the least count of a mere scale is
ten - thousandth of an inch ) , or hundredth of a millimeter
ten - thousandth of an inch ) , or hundredth of a millimeter