Certified coated metal plates and polystyrene blocks are ideal for verifying the accuracy and operation of coating thickness gages and are an important component in fulfilling both ISO and in-house quality control requirements.
Many organizations require verification of gage accuracy at the test site each time a coating thickness gage is put into service and at frequent intervals during use. Ideal for this purpose, DeFelsko certified coating thickness standards have measured values traceable to a National Metrology Institution.
Certified Plastic Shims (foils) provide an economical alternative to coated metal plates. They have a reduced accuracy of ±2 µm (±0.08 mil). A coating thickness gage measures shim thickness when this shim is placed over a smooth metal surface (zero plate).
Non-Certified Plastic Shims (foils) provide a quick operational check of the instrument and they allow the user to perform practice measurements when placed over metal.
Alternatively, they can be placed over an uncoated metal substrate. They are not suitable for use with magnetic pull-off gages.
Shims overview:
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Zero Plates are available as uncoated precision machined steel or aluminum (6061-T6) in a variety of plate sizes.
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Use with Certified Coated Metal Standards
Coated Metal Standards for magnetic and eddy current gages usually include an uncoated zero plate. The first gage measurement is taken on the zero plate to verify that the gage measures zero correctly. If not, electronic gages can usually be adjusted to "0" on the zero plate. After this adjustment is performed, the gage should measure within tolerance on the coated standards.
Use with certified and non-certified plastic shims and polystyrene blocks
A zero plate provides a convenient base onto which plastic shims and polystyrene blocks can be placed for verification purposes. Check zero, adjust to "0" if necessary, then place the shim/block on the zero plate and measure.
Substitute as a base for materials without a substrate
Zero plates can be used to provide a substrate where none exists. Large sheets of material such as paper, plastic, fabric and rubber can be measured with a coating thickness gage by placing the material over the zero plate. This is useful when the measured item is too large to access with a micrometer or other device. For example the screen printing industry uses zero plates to measure the thickness of a the "substrate" being printed.
Certified thickness Standards are used to verify the accuracy and operation of coating thickness gages and are an important component in fulfilling both ISO/QS-9000 and in-house quality control requirements. Contracts often specify that coating thickness measurements be taken by gages whose measurement accuracy is traceable to a National Metrology Institute such as NIST or PTB.
Standards are typically purchased as an accessory to DeFelsko coating thickness gages. Many customers find it more practical to verify the accuracy of their own gages in-house, rather than utilize DeFelsko’s calibration services. This is particularly true when many gages are in use and/or when accuracy verification is performed often.
There are 5 types of coating thickness Standards available from DeFelsko:
Certified Coated Metal Plates are the best solution for verifying the calibration, accuracy and operation of most magnetic, eddy current or ultrasonic coating thickness gages including magnetic pull-off gages as well as many competitive models. They fulfill both ISO and in-house quality control requirements. At ±0.43 µm Certified Coated Metal Plates are our most accurate solution. A durable epoxy coating over 1018 steel or 6061-T6 aluminum and protective binder ensures long life.
Certified Polystyrene Blocks are for use with gages that measure over 1500 µm (60 mils) with an accuracy of ±(2.5 µm + 0.05% of thickness) [±(0.1 mil + 0.05% of thickness)].
Certified Plastic Shims (foils) provide an economical alternative with a reduced accuracy of ±2 µm (±0.08 mil). A coating thickness gage measures shim thickness when placed over a smooth metal surface (zero plate). Alternatively, they can be placed over the customer’s uncoated substrate. They are not suitable for use with magnetic pull-off gages.
Non-Certified Plastic Shims (foils) provide a quick operational check of the instrument and they allow the user to perform practice measurements when placed over metal. A set is included with most electronic DeFelsko coating thickness gages. They are not suitable for use with magnetic pull-off gages.
Zero Plates are uncoated steel or aluminum disks. A zero plate is included with most coated metal sets. The first gage measurement is on a zero plate to verify that the gage measures zero correctly. Electronic gages can usually be adjusted to “0” if necessary. A zero plate is also a convenient base onto which a plastic shim or polystyrene block can be placed for measurement.
Standards should be replaced when they become visibly worn or scratched.
Your electronic PosiTector and PosiTest gages come with NON-CERTIFIED PLASTIC SHIMS for use as a quick reference out in the field or on the floor. But these non-certified plastic shims are not ideal for verifying gage accuracy for the following reasons:
We include non-certified shims with our electronic gages to provide a quick verification of gage operation and allow the user to perform practice measurements when placed over metal.
Yes, our Standards may also be used with many competitive gages provided they operate on magnetic, eddy current, or ultrasonic principles.
Certified Standards are used to verify the accuracy and operation of a coating thickness gage. Select the Standard that most closely matches the measuring range of your gage. See our Ordering Chart for assistance.
In most instances, it will be more economical to trade-in Standards for a new set. Trade-in reduces the price of new Standards by 20%.
Use with Certified Coated Metal Standards
Coated Metal Standards for magnetic and eddy current gages usually include an uncoated zero plate. The first gage measurement is taken on the zero plate to verify that the gage measures zero correctly. If not, electronic gages can usually be adjusted to "0" on the zero plate. After this adjustment in performed, the gage should measure within tolerance on the coated standards.
Use with certified and non-certified plastic shims and polystyrene blocks
A zero plate provides a convenient base onto which plastic shims and polystyrene blocks can be placed for verification purposes. Check zero, adjust to "0" if necessary, then place the shim/block on the zero plate and measure.
Substitute as a base for materials without a substrate
Zero plates can be used to provide a substrate where non exists. Large sheets of material such as paper, plastic, fabric and rubber can be measured with a coating thickness gage by placing the material over the zero plate. This is useful when the measured item is too large to access with a micrometer or other device. For example, the screen printing industry uses zero plates to measure the thickness of the "substrate" being printed.
Shims, sometimes referred to as foils, are small, colored plastic strips of varying thicknesses between ~25 µm (1 mil) and ~1.5 mm (60 mils). They measure 3 x 8 cm (1 x 3 inches). Shims are commonly used to simulate a coating.
For electronic magnetic and eddy-current gages, they are placed onto an uncoated piece of ferrous or non-ferrous metal, and then measured with the gage. Shims may be used individually or stacked to create additional thicknesses.
Ultrasonic coating thickness gages can only measure one shim thickness at a time. The shim must be placed over a flat, rigid object such as a glass pane. The substrate material does not have to be the same material as the material being tested.
Although they are made of the same material and cut to the same dimensions, there is a difference in accuracy, packaging and purpose. Neither is suitable for use with magnetic pull-off gages.
Certified Plastic Shims (foils) provide an economical alternative to coated metal plate Standards with a reduced accuracy of ±2 µm (±0.08 mil). Gage performance can be conveniently verified in the field or in the lab on a regular basis as called for by some international test methods. Shims are placed over a smooth metal surface (zero plate) and a measurement taken. These strips of flat polyester can be used to adjust (optimize) a coating thickness gage in the intended range of use directly over the customer's uncoated substrate.
Certified Plastic Shims are sold individually or as a complete set of eight. Each Certified Shim is individually serialized and labeled with its measured thickness (mils and microns) obtained with measurement equipment traceable to NIST. They are packaged in their own plastic protective pouch. One Certificate of Calibration showing traceability to NIST is included with each shim or set of shims. Their labeled thicknesses are accurate to within ±2 µm (±0.08 mils). They are for use with electronic magnetic, eddy-current and ultrasonic coating thickness gages.
Non-Certified Plastic Shims (foils) are used to provide a quick verification of gage operation when placed over metal and they allow the user to perform practice measurements.
Non-Certified Shims are sold as a set of five packaged in one cardboard envelope. Their labeled thicknesses have accuracies ranging from ±5 to 20%. One set is included with most DeFelsko electronic coating thickness gages. They are for use with electronic magnetic, eddy-current and ultrasonic coating thickness gages.
When adjusting to a shim thickness, resultant gage measurements are less accurate and must be recalculated by taking into account the tolerances of both the instrument and the shims. When shims are used it is necessary to be aware of the possibility of additional measurement errors. Factors experienced with plastic shims that are not usually present with coated metal plate Standards include (but are not limited to):
Shims, which are permissible for adjusting electronic gages with constant pressure probes should not be used for adjusting mechanical pull-off gages including the PosiTest FM and PosiPen. Shims can act as a leaf spring and cause the probe of a magnetic pull-off gage to be "pushed" off the surface prematurely, resulting in an erroneous reading.
Yes, but the cost effective alternative is to trade them in on the purchase of new ones when they become visibly scratched or worn. Trade-in reduces the price of new Certified Plastic Shims by 20%. Additionally, one or more shims can be purchased separately to complete a set.
Coated metal standards require little maintenance. If plates become dirty, the epoxy surface can be gently cleaned with a cotton swab dipped in isopropyl alcohol. Do not clean the exposed metal surfaces with alcohol as this will remove any protective films. To prevent rusting, the steel standards come complete with corrosion inhibitor paper and may require periodic application of a light machine oil or 3-in-1 oil to the exposed metal surfaces. Do not apply oil to the epoxy or labeled surfaces. The aluminum plates should not require any maintenance to the exposed metal surfaces. When not in use, all coating thickness Standards should be stored in a cool, dry place.
Exposure of the epoxy covered steel to magnetic fields may cause the plates to become slightly magnetic. Magnetism in steel plates can affect readings taken with gages using magnetic principles. Do not store epoxy coated steel plates near magnetic sources. If your plates get exposed to a magnetic source they can be restored by using a degausser.
The polystyrene thickness standards are recommended for use with several models of ultrasonic gages. Ultrasonic gages emit a high frequency pulse of sound that travels through the material and reflects back when it encounters a different density material. The thickness of the material is calculated based on the time for the reflection (or echo) to be received and the speed of the sound in the material. Most ultrasonic gages are preset with a ultrasonic velocity that is representative of most coatings. Improved accuracy can be achieved by adjusting the gage's ultrasonic velocity to exactly match the material being measured. Some gage models allow you to directly input the material's velocity if it is known. Other models calculate the material's ultrasonic velocity by measuring a known thickness of a representative material. DeFelsko provides the ultrasonic velocity to allow the calibration standards to be used with either method.
Each national body has an organization(s) responsible for coordinating the national measurement system that provides traceability of measurement results to reference standards that are internationally recognized. The body in the US responsible for this is National Institute of Standards and Technology (NIST). If equipment is calibrated in another country the calibration of that equipment will reference the respective nation's responsible organization. Physikalisch-Technische Bundesanstalt (PTB) is Germany's equivalent of NIST.
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Stated accuracy of Td is ±3C for Td from -40 to 80C.
The following charts illustrate the maximum error of Td with respect to Ta and RH.
View PDF of Accuracy Statement here.
The innovative PosiPatch uses a magnetic ring to hold it against the surface, so no adhesive is required. This means that the PosiPatch isn’t destroyed when removed from the surface, unlike conventional patches. After rinsing with deionized water, the PosiPatch can be used again.
The PosiPatch can be reused multiple times until water begins to leak through the air-permeable membrane or the seal against the substrate.
In our tests on freshly blasted steel with a typical 50-100 micron (2-4 mil) profile, PosiPatches were reused dozens of times with no noticeable wear or leakage. Patch life will vary depending on use- if dragged along the substrate, lifespan will be reduced.
We believe that 10 uses is a very conservative estimate of lifespan and still yields the lowest per-test cost of any commercially available Bresle Method Patch. The below tables compare the per-test costs of various options, using competitive prices found online.
If performing 10 tests, and reusing the PosiPatch:
Replica Tape provides a simple way to obtain an impression of a surface for analysis. It consists of a layer of crushable plastic micro foam affixed to a 50.8 μm (2 mil) incompressible polyester film.
When compressed against a roughened surface, the foam collapses and acquires an impression, or reverse replica, of the surface. It is available in a number of grades to accommodate measurements in different profile ranges.
Placing the compressed tape (replica) into the PosiTector RTR gives a measure of the average maximum peak-to-valley height of the surface roughness profile.
Annotate images using drawing tools—ideal for identifying a specific location or area within an image
Unequal pulling force during testing caused by uneven adhesive bond lines and coating surfaces can result in random, unexplainable readings. To obtain more repeatable and meaningful adhesion measurements, it is imperative that the pulling force applied to the test dolly is uniformly distributed over the surface being tested.
Both the PosiTest AT-M manual and PosiTest AT-A automatic models compensate for misalignment. The self-aligning, quick-coupling actuator and spherical articulating dolly head enable uniform distribution of the pulling force over the surface being tested, preventing a one-sided pull-off.
Two grades of Testex™ Press-O-Film™ replica tape, “Coarse” and "X-Coarse", are available to span the primary range of surface profiles for the coatings and linings industry –– 20 to 115 µm / 0.8 to 4.5 mils.
An unfortunate characteristic of replica tape is that conventional spring micrometer measurements are most accurate near the middle of each grade's range and least accurate at the outer ends of each grade's range. That is why two other grades, Coarse Minus (< 20 µm / 0.8 mils) and X-Coarse Plus (> 115 µm / 4.5 mils), are used to check and, if necessary, adjust measurements at the upper and lower ends of the primary range.
Inside the primary range, Coarse and X-Coarse tape share a 38 - 64 μm (1.5 - 2.5 mils) "overlap" region. Measurements with conventional micrometers require a complicated and time consuming procedure of averaging one reading using Coarse grade and one reading using X-Coarse grade to achieve reasonable accuracy.
With a single measurement, the PosiTector RTR produces a more accurate peak-to-valley height measurement HL from Coarse or X-Coarse tapes that has been adjusted for their non-linearity. There is no need to average two or more replicas from different grades of tape AND there is no need to subtract the 50.8 μm / 2 mils of incompressible polyester film. The advantages are a reduction in measurement uncertainty, inspector workload, likelihood of error, and the number of replicas needed by inspectors to assure accuracy.
The PosiTector RTR can also display a height value (H) that is comparable to what conventional analog spring micrometers would display after the 50.8 μm / 2 mils of incompressible polyester film has been subtracted.
Magnetic pull-off gages use a permanent magnet, a calibrated spring, and a graduated scale. The attraction between the magnet and magnetic steel pulls the two together. As the coating thickness separating the two increases, it becomes easier to pull the magnet away. Coating thickness is determined by measuring this pull-off force. Thinner coatings will have stronger magnetic attraction while thicker films will have comparatively less magnetic attraction. Testing with magnetic gages is sensitive to surface roughness, curvature, substrate thickness, and the make up of the metal alloy.
Magnetic pull-off gages are rugged, simple, inexpensive, portable, and usually do not require any calibration adjustment. They are a good, low-cost alternative in situations where quality goals require only a few readings during production.
Pull-off gages are typically pencil-type or rollback dial models. Pencil-type models (PosiPen shown in Fig 1) use a magnet that is mounted to a helical spring that works perpendicularly to the coated surface. Most pencil-type pull-off gages have large magnets and are designed to work in only one or two positions, which partially compensate for gravity. A more accurate version is available, which has a tiny, precise magnet to measure on small, hot, or hard-to-reach surfaces. A triple indicator ensures accurate measurements when the gage is pointed down, up, or horizontally with a tolerance of ±10%.
Rollback dial models (PosiTest shown in Fig 2) are the most common form of magnetic pull-off gage. A magnet is attached to one end of a pivoting balanced arm and connected to a calibrated hairspring. By rotating the dial with a finger, the spring increases the force on the magnet and pulls it from the surface. These gages are easy to use and have a balanced arm that allows them to work in any position, independent of gravity. They are safe in explosive environments and are commonly used by painting contractors and small powder coating operations. Typical tolerance is ±5%.
Eddy current techniques are used to nondestructively measure the thickness of nonconductive coatings on nonferrous metal substrates. A coil of fine wire conducting a high-frequency alternating current (above 1 MHz) is used to set up an alternating magnetic field at the surface of the instrument's probe. When the probe is brought near a conductive surface, the alternating magnetic field will set up eddy currents on the surface. The substrate characteristics and the distance of the probe from the substrate (the coating thickness) affect the magnitude of the eddy currents. The eddy currents create their own opposing electromagnetic field that can be sensed by the exciting coil or by a second, adjacent coil.
Magnetic film gages are used to non-destructively measure the thickness of a nonmagnetic coating on ferrous substrates. Most coatings on steel and iron are measured this way. Magnetic gages use one of two principles of operation: magnetic pull-off or magnetic/electromagnetic induction.
Magnetic pull-off gages use a permanent magnet, a calibrated spring, and a graduated scale. The attraction between the magnet and magnetic steel pulls the two together. As the coating thickness separating the two increases, it becomes easier to pull the magnet away. Coating thickness is determined by measuring this pull-off force. Thinner coatings will have stronger magnetic attraction while thicker films will have comparatively less magnetic attraction. Testing with magnetic gages is sensitive to surface roughness, curvature, substrate thickness, and the make up of the metal alloy.
Magnetic induction instruments use a permanent magnet as the source of the magnetic field. A Hall-effect generator or magneto-resistor is used to sense the magnetic flux density at a pole of the magnet. Electromagnetic induction instruments use an alternating magnetic field. A soft, ferromagnetic rod wound with a coil of fine wire is used to produce a magnetic field. A second coil of wire is used to detect changes in magnetic flux.
These electronic instruments measure the change in magnetic flux density at the surface of a magnetic probe as it nears a steel surface. The magnitude of the flux density at the probe surface is directly related to the distance from the steel substrate. By measuring flux density the coating thickness can be determined.
PosiTector users can capture and save an image copy of the current gage display by simultaneously pressing both the (-) and (+) buttons. The last 10 screen captures are stored in memory and can be accessed within the PosiSoft USB Drive.
Statistics mode continually displays/updates average, standard deviation, min/max thickness and number of readings while measuring.
Display Languages: English, French, German, Spanish, Chinese, Japanese, Portuguese, Italian, Norwegian, Russian, Czech, Polish and Korean.
All PosiTector 6000 regular separate probes are suitable for underwater measurement and are available with extended cable lengths up to 250 feet / 75 meters.
Ideal for measuring coating thickness on underwater pipes, ships, bulkheads, offshore oil rigs or anywhere extended reach is required.
Maximum cable lengths vary depending on probe type...
Extended cable lengths are also available for ferrous micro probes (F0S, F45S, F90S) and FKS probes (thick coatings) – up to 50 ft (15 m).
Note: Micro probes and FKS probes do not support underwater usage
Contact us for additional information including lead time.