Precise sensors for thickness measurement | Micro-Epsilon

01 Sep.,2025

 

Precise sensors for thickness measurement | Micro-Epsilon

It is important to know the thickness of the plates for the manufacture of aluminium plates. The non-contact profile measuring system measures the profile of the plates using a capacitive sensor. At the same time, the width of the plate is determined during the measurement. The reversing rolling stand and the following roller stands can be better adjusted using the data obtained. The system is integrated in the existing roller track. Installed directly before the cropping shear where the plate is stationary for the cut, the production process is not impaired.

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In the production of battery separators the in-line monitoring of the profile thickness is an important measurement task within the framework of quality assurance. A measurement system with high spatial resolution and a high sampling rate is needed for the determination of the profile structure. This task represents one of the classical fields of application for the laser-based triangulation sensor in the Series ILD . The battery separator is manufactured in an extrusion process. For the thickness measurement the optical sensors are mounted on a welded C-frame. This traverses on air bearings without making physical contact on a hard rock base. In this way the vibration of the top belt is minimized and a precise measurement facilitated.

It is often the case for sheet machining that sheets must be transported individually in machines. Therefore, it is essential that only one sheet gets into the machine. If two sheets are on top of each other, the process will be halted. This task is resolved in a simple way using thickness measurement. If the current measured value is different from the thickness of one sheet, an error is detected. The measurement is independent of the absolute position of the sheet in the measuring gap. Depending on the requirement, laser, optical, capacitive or eddy current sensors can be used for this.

optoNCDT ILR-100 laser distance sensors from Micro-Epsilon measure the coils based on the phase comparison method. For this measurement task, a sensor is mounted at a distance of 0.2 to 10 m facing the radius of the coil. It continuously measures the distance to the coil. As the diameter of the steel strip coil is constantly reduced by the unwinding process, the distance between the coil and the sensor consequently increases. The sensor reliably detects this change in distance and transmits it as a measurement value via the RS422 serial interface to the production process control system. An early warning message can now be issued via the control system, even before the material has been completely unwound.

When producing potato crisps, factors such as consistency, quality and taste depend to a significant degree on the thickness of the potato slices used. Depending on the process parameters and the condition of the tools used, the thickness of the cut slices changes slowly but steadily during the production time. This is why it is important to continuously monitor the thickness during production by using the scanCONTROL -50BL sensor. The sensor projects a laser line onto a conveyor belt, which continuously guides sample slices along it.

A special measuring system has been developed for the quality control of display glass. The glass pane is placed on a measuring table by a robot. A measuring arm with several confocal sensors traverses the glass pane there. If any thickness discrepancies are found, the pane is marked as NOK and rejected. The scanCONTROL laser scanner simultaneously circumnavigates the edges and checks these for defects and dimensions. After the check has been completed successfully, the pane is lifted back into the production process and the next measurement is started.

The thickness of manufactured films is frequently a decisive quality criteria in production. Specially developed thickness measurement systems are used as early as possible in the production for the check of the thickness. Dual sensors consisting of two sensors with different measuring principles measure the thickness across the complete width of the film from one side without contact. A thickness profile of the flat film is thus produced using which the production systems can be regulated extremely precisely. The dual sensors are compiled differently depending on the type of film.

A consistent yarn thickness is a prerequisite in the textile industry for high quality products. Therefore, the naturally occurring yarn thickness fluctuations must be eliminated. The yarn is drawn to a constant thickness using a stretching tool. The measured data for controlling the stretching tool are provided by an eddy current sensor which indirectly measures the thickness. The thickness is transmitted to the eddy current sensor using sensing rollers. After the stretching, the result of the processing operation is also checked by an eddy current sensor.

A special measuring system has been developed for the quality control of glass. The glass pane is placed on a measuring table by a robot. A measuring arm with several confocal sensors traverses the glass pane there. If any thickness discrepancies are found, the pane is marked as NOK and rejected. The scanCONTROL laser scanner simultaneously circumnavigates the edges and checks these for defects and dimensions. After the check has been completed successfully, the pane is lifted back into the production process and the next measurement is started.

The specification of the thickness of glass panes is an optimization process between a required mechanical strength and efficient use of materials. In the manufacturing process the glass thickness is measured and the conformance to prescribed tolerances is monitored. The measurement is carried out with displacement sensors working on the eddy-current principle. Here, the sensor hovers over the glass surface and measures through the glass to a metal plate situated behind it. The values can be read off directly on the device; an analog output voltage facilitates further evaluation.

Inner liners are used in every tyre to prevent the air from escaping. As the inner liner is a characteristic relevant to safety of every tyre, there are high requirements for compliance with the target data. An important criterion is the layer thickness. The system for measuring the thickness of inner liners operates without contact and wear-free. The inner liner is routed through the measuring system immediately after the calender roller. A measuring head traverses above the surface. An eddy current sensor measures the distance to the reference roller while an optical micrometer measures the distance to the rubber surface. The system can be integrated in the heating circuit of the calender roller for better temperature compensation.

In the manufacturing of plastic panels, thickness profile measurements must be carried out due to the necessary quality assurance. For this purpose two laseroptical displacement sensors are mounted on a traversing device, one underneath and one above the panel which passes along a defined path. The preprogrammed measuring points are sampled consecutively. Irrespective of the exact height position of the panels, the accurate material thickness is obtained by simple coupling of the synchronously measured distance values from both sensors. The output of the desired measurement log is realized with the aid of a PC system in the fully automatic sequence of the profile measurement table.

In order to protect PCBs from environmental influences such as humidity, they are coated with a protective clear varnish. This ensures error-free operation. The automotive industry in particular demands a minimum thickness for this protective coating.

Up to now, it was not possible to perform a measurement without destroying the target. Confocal sensors from Micro-Epsilon solve this measurement task without making contact with the target and therefore in a non-destructive manner. They providethe thickness values in real time.

confocalDT IFS confocal sensors with a measuring range of 1 mm are used. These sensors are characterized by their extremely small measuring spot size of only 8 µm and excellent precision for measuring thin layers.

When optical data carriers are produced, the data are initially transferred to a master. Depending on the number of copies, different dies made of nickel are produced from the master by galvanisation. These dies must show a thickness of 297 µm ± 3 µm for faultless production. It is checked several times during the galvanisation that this dimension is complied with. The company ISEDD GmbH from Bielefeld has developed a measuring device for this which enables fast and accurate inspections of the dies. Capacitive sensors from Micro-Epsilon are used for the thickness measurement.

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Thickness measurement using displacement sensors is a wide application area. Basically there are distinctions between non-destructive/destructive, non-contact/with contact and one-side/two-sided thickness measurement. The Micro-Epsilon measuring techniques for thickness measurement are all emission-free whereby no emissions regulations of any kind have to be complied with.

Thickness measurements must be performed both with contacting as well as with non-contact sensors whereby non-contact measuring techniques show advantages as regards accuracy and measuring speed.

There is also a distinction between one-sided and two-sided thickness measurement. Two-sided thickness measurements are carried out with at least one pair of sensors which are installed together on one axis. This pair of sensors measures the target synchronously. The difference between the measurement results (C-A-B) produces the thickness of the measuring object.

One-sided thickness measurements must only be performed with non-contact sensors. In doing so, the target is only measured with one sensor and either only a part of the target thickness (e.g. layer thickness) or the complete measuring object thickness is measured.

Thickness measurements are mainly used in process control and quality assurance, e.g. for the control of extrusion systems or 100% checking of tube diameters.

Precise thickness specifications are assigned for the manufacture of rubber film which is rolled using calender rollers. Random-sample manual measurements, as previously carried out, are no longer sufficient for today’s demands on quality assurance. Consequently, a system with three fixed tracks has been adapted for in-line inspection of the thickness. For each track an eddy current sensor of Type U6 is built into a jockey follower system which measures against an stainless steel roller. Controllers of the range multiNCDT series 100 are employed for the evaluation electronics. The stainless steel roller represents the reference system for the measurement.

The oil film thickness for combustion engines describes the gap and thus the quantity of oil between piston and cylinder wall. Thus it is sometimes a determining factor for smooth operation and durability. As the oil film can only be integrated and really measured in the firing condition, it is extremely difficult to manufacture sensors for these environmental conditions and then also find space for them. Specially miniaturised eddy current sensors from Micro-Epsilon are capable for this. The smallest with only 2.4 mm external diameter is integrated directly into the cylinder wall and ground to its shape. There, it measures the distance from sensor to piston or the space available for the engine oil for lubrication in every stroke.

To prevent damage, laser-based optical displacement sensors are employed in front of the inlet for profiled sheets in presses to enable the detection of double sheets. The sensors are mounted opposite one another, above and below the passing sheets. Irrespective of the actual position of the sheets, the material thickness is obtained by

simple coupling of the distance signals from both sensors. For adjustment a master sheet for each type of sheet is inserted into the measuring gap and the resulting signal set to zero. The zero value is monitored within a tolerance. The sensors are operated in special protective housings because of the harsh ambient.

Layer thickness measurement belongs to the group of one-sided, non-contact thickness measurement. Basically, only the layer thickness of electrical insulators can be measured for opaque objects. An eddy current sensor penetrates the insulating layer without damage and measures the distance to a layer underneath it. At the same time, a second sensor, a laser triangulator measures the insulating layer. The layer thickness is obtained by offsetting both signals. This method of measuring with two sensors using different principles is called the dual sensor technique by Micro-Epsilon.

A second possibility is the layer thickness measurement of transparent materials using confocal measurement technology. The emitted white light penetrates the measuring object and provides a peak in the signal graph at every material transition. For example, the film thickness between two glass panes can be easily measured in this way.

Application Solutions for Inner and Outer Diameter Measurement

Traditionally, inner diameter measurements were done with hand tools like vernier calipers, inside micrometers, telescope gauges or bore gauges. While these tools offered high levels of precision, they also required time and expertise... making them susceptible to human error.
Today, measurement sensors like laser scanners and optical comparators are commonly used to measure ID/OD. These sensors are highly accurate and work well for difficult-to-reach and contact-sensitive applications.

When looking for the best way to measure outer diameter, there are several important factors to consider, including the shape of the target, the type of measurement system, and the installation environment. Selecting equipment that doesn't adequately meet your needs can lead to insufficient precision and increased man-hours during production, so choosing the right equipment is important. This site is designed to help you discover the best way to perform outer diameter measurements with confidence.

The radius of a cylinder is defined as the distance from its center to any point on its edge, and it’s a linear measurement that extends from the center of the circumference. Since the OD measurement is defined as a straight line passing through the center of the cylindrical space and connecting both sides, we can easily deduce that the radius is ½ of the diameter.
Conversely, the ID measurement is twice the radius of the inner circle. Radius measurements are rather important when it comes to determining the mechanical properties of parts such as gears, wheels, and pulleys.
Find the best measurement method and the right equipment to measure "Radius (R) and Inner Diameter."

When looking for the best way to measure radius (R), there are several important factors to consider, including the type of measurement system and the installation environment. Selecting equipment that doesn't adequately meet your needs can lead to insufficient precision and increased man-hours during production, so choosing the right equipment is important. This site is designed to help you discover the best way to perform radius measurements with confidence.

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