What requirements apply to instruments and controls used to measure, regulate, or record?

Instruments or controls you use to measure, regulate, or record temperatures, hydrogen-ion concentration (pH), sanitizer efficacy or other conditions, in order to control or prevent the growth of microorganisms of public health significance, must be: (a) Accurate and precise as necessary and appropriate in keeping with their purpose; (b) Adequately maintained; and (c) Adequate in number for their designated uses.