1. After long-term natural aging, the rock structure is uniform, the coefficient of expansion is minimal, the internal stress
disappears, and the rock is not deformed, so the precision is high;
2, not afraid of acid, lye erosion, will not rust, do not need to oil, not easy to adhere to the dust, maintenance, maintenance easy and simple, long service life;
3, no scratch, not prevented by constant temperature condition, temperature measurement accuracy can be maintained at room temperature;
4, no magnetization, the measurement can be smooth movement, no hysteresis, not affected by moisture, good planeness.