Glossary of thickness gauging
Calibration refers to a series of operations performed to ascertain
differences between actual equipment values and reference values.*
Confocal multi-colour measurement
Confocal measurement simplifies mounting requirements and enables stable measurement of any surface or shape. The confocal method allows larger measurement ranges and higher accuracy across the entire measurement range.
Dynamic Thickness Gauging System
At the dynamic measuring system, the measuring point changes its position in the whole system, depending on time or path.
Linearity is an indicator of a measurement system‘s capability. The value represents the maximum error value between an ideal value and the actual measurement result. For example, when a target is moved 1 mm using a measurement system with a linearity of ±5µm, the displayed value is said to possibly include an error margin of ±5µm (e.g., 9.995µm to 1.005µm).*
The measuring system remains in the static mode. The Y-coordinate of the measuring system remains unchanged during the measuring process. As the material travels in the X-direction, thickness measuring values are taken along a straight line.
At macro traversing, the Y-coordinate of the measuring system changes dynamical. The system oscillates back and forth between two fixed Y coordinates (Y1 and Y2) at constant speed.The two coordinates Y1 and Y2 result from the two edges of the current material to be measured. Only the movement of the material in X direction produces Thickness Gauging values along a sinusoidal line. The measurement is performed over the whole width of the material.
Macro traversing with track measuring
The macro traversing with track measuring basically works like macro traversing. In addition, the material width to be measured can be subdivided into more tracks with the LTM-S measuring software. Each track has two unique Y coordinates (YS, YE) that determine the track width. This makes it possible to hide tracks (partial areas) during the measurement or to include only relevant tracks for further processing in the measuring data analysis.
Thickness Gauging by using laser technology can only take place with a relative movement between the material to be measured and the lasers.It describes the speed at which the material moves in relation to the laser sensors.
The measuring accuracy of a Thickness Gauging System provides information about how accuracy is achieved in order to respect the specified tolerances within a reliable measuring.
The measuring center point is defined as the point or dimension in which both laser beams (Z direction) meet at an optimal measuring distance. The reference is always the lower edge of the measuring system.
Depending on the customer‘s application and the corresponding dimensions of the measuring system, lasers with a defined sampling rate are used. Using the sampling rate [Hz] and the material speed [m/ s] known by the customer, the measuring density (number of measured alues per path) can be calculated.
The measuring distance is the distance range between laser to the material (Z - direction) in which a plausible measuring data acquisition is possible.
The goal ist o guide the material to be measured along the lasers with a constant distance. Ideally, the distance between laser and material should be identical to the optimal measuring distance.
Depending on the requirements or the selected Thickness Gauging System, a wide range of measuring modes are possible. These can be selected in the LTM-S measurement software and stored depending on the product. Basically, dynamic measurement systems (LTM-SMART, LTM-MAXI, LTM-ULTRA) offer a wider choice of measurement modes.
ROLAND ELECTRONIC Thickness Gauging Systems allows following measurement
modes, according to each type:
• Line measurement
• Macro-Taversing with track measurement
The measuring range is the range that a sensor can perform measuring. Measuring ranges are generally written as ±xx mm based on the reference distance.*
Measuring system analysis according to method 1
In order to comply the measuring quality, the accuracy or correctness of the measurement during the production process, the LTM-BASE,
LTM-SMART, LTM-MAXI and LTM-ULTRA Thickness Gauging Systems are equipped with a corresponding software tool to perform the measuring system analysis according to method 1.
During micro - traversing the Y - coordinate of the measuring system changes dynamically. The system oscillates back and forth between two freely selectable Y coordinates (Y1 and Y2) at a constant speed. The resulting traversing path is always smaller than the current bandwidth or material width. As the material moves in the X direction, thickness measurements are taken along a sinusoidal line.
The reference distance is the sensor heads default zero point. This is commonly represented as the distance from the bottom of the sensor head to the center of the measuring range.*
Repeatability represents the overall difference in a measurement value taken at the same location on a target.*
Sampling frequency / Sampling speed
The sampling frequency / sampling speed represents the number of data points the measurement system can measure per second. A measurement system with a sampling frequency of 100 Hz can perform 100 measurements in 1 second. Measurement systems with faster sampling frequencies are capable of providing more accurate target measurements with inline measurement, and because multiple averaging processes can be performed at once, measurements will be stable.*
Static Thickness Gauging System
At the static measuring system, the measuring point remains unchanged in relation to the whole production line system.
Thickness Gauging Software LTM-S
The LTM-S (internal client) Thickness Gauging Software supplied with the LTM-BASE, LTM-SMART, LTM-MAXI and LTM-ULTRA systems includes all the tools necessary to operate, to process, to display and to provide the recorded thickness gauging values.
A laser hits the target, light reflected off of the target is concentrated through the receiving lens and is focused onto the light receiving element. If the distance from the sensor to the target changes, the angle of the reflected light changes causing the position of the received light to change on the light receiving element. This change is proportional to the movement amount of the target, because we know the distance between each position on the light receiving element we are able to determine displacement.*
Unit Passing Line
The unit passing line defines the dimension which results from the distance between the reference edge of the unit (Z-direction) and the measuring center point minus half the material thickness. As a measure of the material thickness, the most commonly measured nominal thickness is used.
The working area is defined as the area (Z-direction) in which the material to be measured may move to the working position in order to ensure a plausible measurement data recording. The working area can not be fully utilized.
* Courtesy of: Keyence, „Measurement library“, www.keyence.com/ss/products/measure/measurement_library