大型工程常由拌合机来生产混凝土。混凝土是由水泥、碎石和砂加水拌合而成的。水和水泥的重量比（水灰比）对拌成的混凝土质量影响很大。在工地，由于砂的含水率经常变化，常破坏正常的水灰比。所以很需要随时测定砂的水分，以便及时调整加水量，保持正常的水灰比，从而保证混凝土的质量。

In the process of the concrete production

water and cement must be kept at suitable proportion; therefore

in order to adjust the quantity of water required

we must measure the moisture of the sand at any moment. The neutron moisture gauge may fulfil this task. The precision of measuring moisture is <0.4% (weight) . In this paper the neutron moisture gauge for concrete mixer and its calibrations and applications are reported.