Has zero error.
The zero error in the vernier calipers and micrometer screw gauge when the O mark on the main scale is not in line with the pointer.
The first step is to find the zero error and hence the zero correction. Rotate the micrometer until the fixed and movable jaws contact each other - not too hard and not too soft but just right, you should geta feel for this. Rarely will a micrometer will read zero. You need to figure out the zero error. It may be positive or negative. If the zero error is positive then the zero correction is negative and vicevers. Now open the micrometer and insert the object to be measured and close the micrometer with ideally the same sense of pressure you felt when you found the zero error. Now read the micrometer. You add the zero correction to get the true value.
This micrometer has zero error.The zero marking on the thimble is below the datum line. So this micrometerhas a positive zero error.In this case we will take the reading on the thimble.Thimble reading = 0.03 mmSo the micrometer has a zero error of +0.03 mm.Whatever reading we take on this micrometer we would have to subtract +0.03 mmThe zero marking on the thimble is above the datum line. So this micrometerhas a negative zero error.In this case we will have to count the number of divisions on the thimble between the zero marking and the datum line.No. of divisions = 3Measurement of each division = 0.01mmSo the micrometer has a zero error of -0.03 mm.Whatever reading we take on this micrometer we would have to subtract -0.03 mm
It depends on what type of instrument is being used.If it is a Vernier caliper,the zero error is caused when the zero on the vernier scale is shifted either to the right(+ve error) or the left(-ve error) of the of the zero mark on the main scale.The way to find the zero error is quite similar to the Micrometer screw gauge one but still they are different due to their different parts.For the Micrometer screw gauge,the zero error occurs when the zero mark on the circular scale is either shifted up(-ve error) or shifted down(+ve) from the horizontal line on the main scale(sleeve).
The gap between the zero of the main scale division and zero of the circular scale division when the circular scale is tightly fixed is known as zero errror of micrometer screw gauge.
This is the measurement recorded when, in fact, it should be 0. It is the measurement when there is nothing to measure but the reading is not exactly 0 because the calibration has gone off.
we can find the zero error by closing the jaw of screw guage if the zero of main scale(MS) is concide with the zero of circular scale (CS) there is no zero error and if they are not concide there is a zero error in screw guage .
InstrumentA micrometer is a guage measuring device used to measure small lengths with an accuracy of 1\100 mm Unit of lengthA micrometer is exactly one millionth of a meter the least is 0 (zero)
if the zero of vernier scale lies on the right side of the zero of the main scale , then error is known as a positive error .
The zero error of vernier calliper is defined as :-The zero error is equal to the distance between the zero of the main scale and the zero of the vernier scale.