A licensed public weighmaster shall: (1) Keep the scale or scales upon which he or she weighs any commodity or thing, in conformity with the standards of weights and measures; (2) carefully and correctly weigh and certify the gross, tare, and net weights of any load of any commodity or thing required to be weighed; and (3) without charge, weigh any commodity or thing brought to his or her scale by the director or peace officer, and issue a certificate of the weights thereof.