1.What are the core standard materials for calibration?
Standard thickness plates (standard samples): These are crucial calibration tools. They are typically a set of thin steel sheets calibrated and certified by an authoritative metrology institution (such as the National Institute of Metrology, China), covering the instrument's measurement range. The standard plates must have clear traceability and uncertainty.
Step blocks: Used for multi-point calibration, checking the instrument's linearity across the entire measurement range.
Zeroing plate/base plate: Used to establish the zero point of the measurement reference.
2.What are the main calibration steps?
Cleaning and Preheating: Ensure the measuring head's optical window (non-contact) or probe (contact) is free of oil and oxide scale. Simultaneously, ensure the instrument is powered on and preheated to a stable operating state.
Zero-Point Calibration: Place the instrument's measuring head in a sample-free state (or place it on a dedicated deviation-free substrate) and adjust the displayed value to zero.
Range Calibration (Multi-point Calibration):
Place a standard plate of known thickness in the measurement area.
For non-contact instruments (such as X-rays), the instrument measures the amount of radiation attenuation passing through the steel plate and compares it to the known thickness of the standard plate, automatically correcting the internal curve.
For contact instruments, static calibration is performed using a standard plate to simulate online operating conditions, comparing the measured displacement with the standard value.
Typically, at least three different thicknesses of standard plates (low, medium, and high) are required for calibration to ensure accuracy across the entire range.
3.How can linearity and repeatability be verified?
Repeatedly measure the same standard plate and observe the fluctuation of the data (repeatability); measure different points and observe the consistency (linearity).
4.Does the standard plate need to be compatible with the material being tested?
If measuring cold-rolled steel sheets, the standard sheet must also be made of steel. If measuring aluminum alloys or copper, a standard sheet of the corresponding material must be used.
5.What are the key points to note?
Environmental Consistency: The ambient temperature and humidity during calibration should be as close as possible to the production environment, as temperature changes can cause thermal expansion of the steel plate and instrument drift.
Periodic Mandatory Verification: According to national metrological regulations, thickness gauges used for trade settlement or quality control are subject to mandatory verification and must be verified periodically (usually annually) by a legally authorized metrology institution, which will issue a verification certificate.
Integrated Testing and Validation: After calibrating the thickness gauge, it is often necessary to perform integrated testing with an automatic thickness control system to ensure control accuracy.