Business and Professions Code § 12504
CHAPTER 5. Weighing and Measuring Devices
Upon the written request of any person who intends to use or sell for commercial purposes any weight or measure, or weighing or measuring instrument in any county, the sealer for such county shall test or cause to be tested, as soon thereafter as is practicable, the weight or measure, or weighing or measuring instrument referred to in the request.
Such written request shall not relieve the person making it from any violation of the provisions of this division or of the responsibility for using or selling any incorrect or unsealed weight, measure, or weighing or measuring instrument.