X-Ray Thickness Gauge: How Does it Compare with Direct Contact and Optical Gauges?

Non-contact thickness and coating weight gauges ensure correct measurements and help companies to minimize raw material waste. They do this by calculating the dimensions of thickness or various types of coatings to meet the exact specifications of the end products. It is vital to get accurate thickness measurements of the finished applications. Otherwise, incorrect thickness computations will affect the final product’s mechanical properties.

When it comes to measuring metallic coatings, you will come across several types of thickness gauges. The most common among them are x-ray, direct contact, and optical gauges. But which is the best and most suitable choice for your industry?

Direct contact gauges are not affected by reactions with alloys. But the mechanical tolerances of the frame make it difficult to measure anything near the strip’s centerline. Moreover, direct contact gauges are prone to micro-vibrations and noise. This means that the signal must be filtered to minimize the noise. Sometimes, this process results in delays.

You may then be considering optical laser gauges. This category of gauges operates on the principle of using triangulation to compute distance measurements. But they come with their own set of disadvantages, especially when you deploy them in steel mills. Environmental effects of both hot mills and cold mills create huge challenges for optical sensors to accurately gauge.

You cannot trust the performance of laser gauges in industries that generate huge amounts of steam or mist. This is a common phenomenon in rolling mills. Plus, its laser camera technology sometimes even distorts the measurement resolution, up to a few microns. This small difference might not hamper process line applications, but it is not suitable for high-speed cold rolling mills. Additionally, the design of its sensor frame exhibits a short arm length to minimize the effect of thermal expansion on the outcome. This leads to restrictions in the allowable strip thickness. The total measurement area gets restricted, even up to a few centimeters.

Finally, non-contact x-ray and isotope-based thickness gauges are the only possible technology that can be deployed for accurate closed loop and AGC measurement applications with tough environmental conditions that you may find in a hot strip mill. These gauges emit photons at a high frequency, which is 1000x that of regularly available isotopes. X-ray gauges give the most accurate measurements since they work on radiation detection and have the best signal to noise ratio. You might think that you can achieve the same level of accuracy by using multiple isotope pellets to enhance the signal, but this practice is unsafe.

The choice of the perfect thickness gauge depends on the measurement accuracy levels you desire for your finished product. Therefore, we strongly advise you to understand the precise requirements and then choose the technology that best suits your needs.