What precautions should be taken when using a Vickers hardness tester?

Taiwan Nakazawa answers for you: The Vickers hardness tester itself will produce two types of errors: one is the error caused by the deformation and movement of its parts; the other is the error caused by hardness parameters exceeding the specified standards. For the second type of error, the hardness tester must be calibrated with a standard block before measurement.
Regarding the calibration results of the Rockwell hardness tester, a difference within ±1 is qualified. For stable values with a difference within ±2, a correction value can be given. When the difference is outside the range of ±2, the hardness tester must be calibrated and repaired or another hardness testing method must be used for determination.
Each hardness scale has a de facto range of application, which should be selected correctly according to regulations. For example, when the hardness is higher than HRB100, the HRC scale should be used for testing; when the hardness is lower than HRC20, the HRB scale should be used for testing. Because when exceeding its specified testing range, the precision and sensitivity of the hardness tester are poor, the hardness values are inaccurate, and it is not suitable for use. Other hardness testing methods also stipulate corresponding calibration standards. The standard block used for calibrating the hardness tester cannot be used on both sides, because the hardness of the standard surface and the back surface is not necessarily consistent. It is generally stipulated that the standard block is valid within one year from the date of calibration.