Precise sensors for thickness measurement | Micro-Epsilon

07 Jul.,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.

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.

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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.

How to Measure the Diameter and Wall Thickness of Steel Pipes? -

Measuring the diameter and wall thickness of steel pipes accurately is essential for various engineering, construction, and manufacturing applications. There are different tools that can be used for this purpose, including calipers and micrometers. In this section, we will explain how to measure the diameter and wall thickness of steel pipes using these tools.

Here are two common measuring instruments used for measuring the diameter and wall thickness of the pipe:

  1. Caliper: To measure the diameter of a steel pipe, calipers can be employed. Calipers are versatile tools that come in different types, such as vernier calipers or digital calipers. To begin, open the caliper jaws and place them on opposite sides of the pipe. Close the jaws until they make contact with the outer surface of the pipe, ensuring a firm but not excessive grip. Read the measurement displayed on the caliper scale or digital display, which corresponds to the pipe’s outer diameter.
  2. Micrometers: Measuring the wall thickness of a steel pipe can be done using a micrometer. Micrometers are precise measurement instruments that allow for accurate readings. Start by opening the micrometer and positioning the pipe between its spindle and anvil. Gently tighten the micrometer until the pipe is firmly held in place. Read the measurement displayed on the micrometer scale or digital display, which corresponds to the pipe’s wall thickness.

It is important to note that when measuring the wall thickness of a steel pipe, the measurement should be taken at multiple points around the circumference. This helps account for any variations in thickness that may exist. Take several measurements and calculate the average to obtain a more accurate representation of the wall thickness.

Both calipers and micrometers offer reliable and accurate measurements of steel pipe dimensions. However, it is crucial to ensure that the measuring tools are properly calibrated and maintained for precise readings. Regular calibration and inspection of these tools help maintain measurement accuracy and reliability.

In summary, measuring the diameter and wall thickness of steel pipes can be achieved using calipers and micrometers. These tools provide accurate readings, enabling engineers, manufacturers, and professionals to make informed decisions regarding material selection, compatibility, and overall pipe performance.

How to Measure the Outer Diameter and Wall Thickness of a Pipe Using Calipers

Accurate measurement of the outer diameter and wall thickness of a pipe is crucial for various engineering, construction, and manufacturing applications. Calipers are versatile tools that provide precise measurements for these parameters. In this comprehensive guide, we will explain in detail how to measure the outer diameter and wall thickness of a pipe using calipers, ensuring accurate and reliable results.

  1. Choosing the Right Calipers:
    • Select a caliper suitable for the pipe size and measurement accuracy required.
    • Digital calipers offer ease of use with instant and accurate readings, while vernier calipers provide a traditional approach with high precision.
  2. Preparing the Calipers:
    • Ensure that the caliper jaws are clean and free from debris.
    • Check the zero point or calibrate the calipers if necessary to eliminate any measurement errors.
  3. Measuring the Outer Diameter:
    • Open the caliper jaws and position them on opposite sides of the pipe.
    • Gently close the jaws until they make firm contact with the outer surface of the pipe.
    • Take note of the measurement displayed on the caliper scale or digital display.
  4. Measuring the Wall Thickness:
    • Keep the caliper jaws in the same position on the pipe.
    • Open the caliper jaws slightly and realign them to make contact with the inner surface of the pipe.
    • Gently close the jaws until they make firm contact with the inner surface.
    • Take note of the measurement displayed on the caliper scale or digital display.
  5. Calculating the Wall Thickness:
    • Subtract the outer diameter measurement from the inner diameter measurement obtained from the caliper.
    • The resulting value represents the wall thickness of the pipe.
  6. Repeating the Measurements:
    • To ensure accuracy, repeat the measurements at multiple points along the pipe’s length.
    • Take several measurements of the outer diameter and wall thickness, and calculate the average for more precise results.
  7. Recording and Verification:
    • Record the measured outer diameter and wall thickness for future reference or documentation.
    • Double-check the measurements to ensure accuracy and consistency.
  8. Maintenance and Calibration:
    • Keep the calipers clean and well-maintained for optimal performance.
    • Periodically calibrate the calipers to maintain measurement accuracy.

Conclusion: Measuring the outer diameter and wall thickness of a pipe using calipers provides precise and reliable results for engineering, construction, and manufacturing purposes. By following these step-by-step instructions, professionals can ensure accurate measurements, enabling them to make informed decisions regarding material selection, compatibility, and overall pipe performance. Regular maintenance and calibration of the calipers contribute to maintaining measurement accuracy and reliability over time.

How to Measure the Outer Diameter and Wall Thickness of a Pipe Using a Micrometer 

Accurately measuring the outer diameter and wall thickness of a pipe is essential for various engineering, construction, and manufacturing applications. Micrometers are precise measurement instruments that provide accurate readings. In this comprehensive guide, we will explain in detail how to measure the outer diameter and wall thickness of a pipe using a micrometer, ensuring precise and reliable results.

  1. Selecting the Right Micrometer:
    • Choose a micrometer suitable for the size and measurement accuracy required.
    • Micrometers are available in various types, such as digital micrometers and vernier micrometers, each offering unique advantages.
  2. Preparing the Micrometer:
    • Ensure that the micrometer’s measuring faces are clean and free from any debris.
    • Verify the zero point or calibrate the micrometer if necessary to eliminate measurement errors.
  3. Measuring the Outer Diameter:
    • Place the pipe between the micrometer’s spindle and anvil.
    • Gently tighten the micrometer until the pipe is firmly held in place.
    • Read the measurement displayed on the micrometer scale or digital display, corresponding to the pipe’s outer diameter.
  4. Measuring the Wall Thickness:
    • For measuring the wall thickness, ensure that the micrometer’s anvil rests on the outer surface of the pipe, while the spindle touches the inner surface.
    • Gently tighten the micrometer until firm contact is made with both surfaces.
    • Read the measurement displayed on the micrometer scale or digital display, representing the pipe’s wall thickness.
  5. Taking Multiple Measurements:
    • To ensure accuracy, measure the outer diameter and wall thickness at multiple points along the pipe’s length.
    • Take several measurements and calculate the average for more precise results.
  6. Recording and Verification:
    • Record the measured outer diameter and wall thickness for future reference or documentation.
    • Double-check the measurements to ensure accuracy and consistency.
  7. Maintenance and Calibration:
    • Keep the micrometer clean and properly maintained for optimal performance.
    • Regularly calibrate the micrometer to maintain measurement accuracy.

Conclusion: Measuring the outer diameter and wall thickness of a pipe using a micrometer provides precise and reliable results for engineering, construction, and manufacturing purposes. By following these step-by-step instructions, professionals can ensure accurate measurements, enabling them to make informed decisions regarding material selection, compatibility, and overall pipe performance. Regular maintenance and calibration of the micrometer contribute to maintaining measurement accuracy and reliability over time.

If you want to learn more, please visit our website Precision maintenance-free steel pipe diameter measuring gauge.