JJG (Light Industry) 50.1-2000 "Paper and Cardboard thickness tester verification procedure" specifies the verification and use requirements for paper and Cardboard thickness testers with a measuring range of not more than 4mm. The procedure is suitable for manual and electric thickness testers and covers the principle of contact measurement method. The specification requires verification of the thickness indication Precision, Zero Stability, Appearance and the function of each component of the instrument. The verification items include measurement head and anvil surface roughness, flatness and contact pressure to ensure the measurement accuracy of the instrument. The verification period is generally one year to ensure the long-term stability and reliability of the instrument.