odel：YC-HSP540D
Origin：Beijing
Purpose：A special instrument for measuring the change of length (volume) of concrete specimens during hardening under certain environmental conditions.

The shortcomings of available horizontal concrete shrinkage expansion meter:
(1) Hard steel or quartz glass is recommended for the calibration rod material in the standard, but the available calibration rod in the market is mostly made of stainless steel. Its linear expansion coefficient is too high, which is easy to cause errors due to the influence of temperature fluctuation.
(2) The accuracy of the micrometer is poor, even if the best electronic micrometer is used, because its measurement error is more than 3um. Generally, the error of the micrometer is more than 5um, which will cause a great error for the shrinkage of concrete specimens in the later period.
(3) Manual reading records during the test process are prone to errors, which is caused by human errors or errors in data transcription.
Moreover, the same specimen needs to be measured more than a dozen times in the whole test cycle. The above error factors will be enlarged continuously, and it is likely that there will be conflicting phenomena between early and later results. We can’t find the root cause of the problem.