Bar diameter gauge has the characteristics of intuitionistic and clear revealing the relationship between rolling parts in rolling process, providing comprehensive analysis of product measurement, better realizing process control, speeding up start-up time, easy to master and adjust the rolling mill, simple operation, cost saving and space saving. Bar diameter gauge measures geometric dimensions such as diameter, cross-section, ellipticity, without measuring blind area, timely and accurately reflects the size change of the measured rolled piece, can alarm various common defects (ears, rollers, etc.) in the rolling process, can carry out statistics and analysis of the measured data, and can communicate with the production system computer in real time, measure data transmission, and also has the functions of real-time communication and data transmission. Correction function. The bar diameter gauge is equipped with the Blue Peng measurement and control software system. Its operation interface screen can display real-time information such as measured outer diameter value, ellipticity, cross-sectional chart, trend chart and so on. It has the function of statistics and analysis, can store historical data for a long time, and has the function of query. It can process the data acquired from the measurement unit (all test values are read and displayed continuously and real-time after processing and filtering). According to the set measurement products, the diameter value, ellipticity, average diameter and other information can be calculated. Bar diameter gauge can display the actual diameter digitally with contour graphic display (cross section). Diameter gauge has alarm function. When the measured value exceeds the upper and lower limit of the preset alarm, the screen will display the alarm with digital color change, and the digital signal and relay output sound and light alarm. Regular parameters such as alarm tolerance, product material and material thermal expansion and contraction coefficient can be set. Bar diameter gauge is suitable for continuous on-line measurement of hot-rolled round steel, thread steel, bar, wire rod, high wire, etc. Real-time display of measurement data and graphics, measurement results can be displayed on the LED large screen display, synchronous display measurement accuracy is high, fast. Real-time recording and storage of measurement data, large amount of data, complete storage of measurement results, suitable for production line quality monitoring, quality tracking and process analysis. It is a good assistant for rolling production line to detect, identify and provide sound and light alarm directly the oversize size and non-roundness of the measured object.