Surface Thickness Calibration

Surface Thickness Calibration

Share This Post


In simple terms, calibration is establishing, correcting, or marking the scales of (anything) in order to determine its quality (something, such as a thermometer tube): to establish the accurate correction factors by calculating the variation from a standard in order to standardize (anything, such as a piece of measurement equipment). On the other hand, different industries define it in different ways. In industry definition, calibration means the documented comparison of the measurement equipment against an already known traceable range value to ensure measurement accuracy and quality.

One needs to only see the major calibration organization’s definitions to understand how difficult the calibrations are. Depending on numerous organizations, numerous definitions of calibration exist. In this blog, you will learn about surface thickness calibration and its use.


 Introduction to Surface Thickness Calibration

For inspectors and applicators, measuring physical characteristics such as coating thickness, surface profile, and the dew point is a typical task. However, an equipment usage ratio and the way of using it measures the accuracy of those equipment’s measurements. Even high-quality electronic instruments might produce inaccurate data if one skips Calibration, Verification, and Adjustment. In this blog, we’ll also talk about the value of a “long form” calibration certificate, the qualifications for performing one, and the applications that can call for field adjustments.


Importance of Surface Thickness Calibration

The main purpose of the calibration is to restore/realign the gauge to meet/exceed the manufacturer’s demanding accuracy.

Surface thickness calibration can achieve:

  • Efficient coating thickness,
  • Good production quality,
  • The established production process,
  • Controlled cost expenditures etc.


When to Recalibrate

Since the accuracy of most of the measuring equipment decreases with usage, periodic calibration (or recertification) is necessary throughout the life cycle of an instrument. Calibration interval is crucial for an equipment’s good functional capabilities. A calibration interval means the predetermined time between an instrument’s calibrations. The majority of manufacturers do not include calibration intervals as part of calibration certificates in accordance with ISO 17025 criteria. Why? Considering that they are unaware of the gauges’ usage frequency, environment, and maintenance level.

If you don’t have experience with an instrument, one year is a good starting interval between calibrations. A good grasp of experience and regular verification can adjust the interval too. Customers with new instruments can utilize the purchase date or servicing date as the beginning of their first calibration interval. The negligible effect of shelf life minimizes the importance of the actual calibration certificate date.



Adjustments in surface thickness calibration

Adjustment of coating thickness gauges is essential. Coating thickness gauges gauge the substrate’s magnetic characteristics rather than the coating’s thickness. Therefore, these characteristics deteriorate with the coating thickness. This happens due to the deterioration of the probe.


Other elements, however, may have an impact on the substrate’s magnetic characteristics. These consist of the following:

  •  Mass
  •  Composition
  •  Geometry
  • Surface roughness

The majority of coating thickness gages are factory calibrated for use with flat, smooth carbon steel. If one performs an adjustment, they can measure precisely on applications with varied surface roughness, geometry, composition, or mass:

Adjustment: aligning gauge readings with a known thickness sample to increase accuracy on a surface.

It’s vital to remember that every adjustment only takes into consideration if the substrate’s shape, composition, and/or mass is in the precise area. An equipment needs additional adjustments frequently if any of these variables change over the portion or work.

In fact, all coating thickness gages are the same. For the best instructions on how to tune your specific instrument, contact the manufacturer or see the user handbook.


Gauges of Surface Thickness Calibration

Pull-off (PosiTest or PosiPen) gauges function by letting a permanent magnet come into direct contact with the coated surface using pull-off (PosiTest or PosiPen) gages. The calibrators can determine the coating thickness value on a scale or display on the gage by measuring and interpreting the force required to remove the magnet from the surface. The thickness of the dry coating, or the distance between the magnet and the steel, determines the nonlinear inverse relationship between the magnetic force binding the magnet to the surface. The calibrators may remove the magnet from a thick coating with less force.

Another type of gauge, the electronic gauge, uses electronic circuitry to translate a reference signal into coating thickness. To function, electronic ferrous gages use two distinct magnetic principles. Some people utilize a permanent magnet that increases the magnetic flux density at the magnet’s pole face when placed close to steel. Coating thickness depend on this change in flux density, which changes inversely to the distance between the magnet and the steel substrate. These changes in magnetic flux density are often measured using hall elements or magnet resistance elements placed at the pole face. Temperature correction is necessary since these elements’ responses are temperature dependent.

 In account of the surface thickness calibration based on electromagnetic induction, other ferrous electronic gauges function. Calibrators create an altering magnetic field at the probe by energizing a coil containing a soft iron rod with an AC current. Probing the steel substrate raises magnetic flux density in the rod, similar to a permanent magnet. A second coil notices this difference. The second coil’s output depends on the coating’s thickness. Due to the temperature dependence of the coil characteristics, these gauges also require temperature adjustment.


Ask about our services

We have been certified by BAB & NABL as an ISO/IEC 17025-approved calibration laboratory. Additionally, we produce and sell Instrument Test & Calibration Benches and Service Field Calibration Equipment. Besides electrical calibration, we also provide Electronic Calibration, Mechanical Calibration, Dimensional Calibration, Temperature Calibration, Moistness Calibration in Humidity Chamber, Weight/Vacuum Calibration, Power/Torque Calibration, Surface Thickness Calibration, Equalizations/Scales Calibration, Hardness Testers Calibration, Autoclaves Calibration.

Please leave a comment below or give us a call if you have any questions about electrical calibration. One of our engineers will be happy to assist you.