Dial indicator hand in wrong position below the zero point
If the dial indicator has turned reverse below the zero point,normally it needs not to calibrate the test force first, just need to use the test block to calibrate the hardness tester ,if the hardness value is accurate, just need to erase the 3000 kg indicate line on the dial indicator with alcohol pad/stick and remark it in the right position, and calibrate procedure step is as below:
1.First use the test block to calibrate the hardness tester and make the dial indicator hand to arrive to 3000kg(now it should be 2900kg due to dial indicator hand below the zero point) for 8 times, and then to read the Birnell indentation diameter and look up the chart to get the Brinell hardness value.
2.Second,to use the same test block to calibrate the hardness tester again, and this time to make the the dial indicator hand to arrive to 3000kg(now 2900kg) for 9 times,and then to get the hardness value, to compare the two times hardness value, if two times hardness value is within the indicator error range, that can certify that the test force and pressure no problem,no need to calibrate it,just re make the 3000kg indicate line in right position.