Question 1

How do you measure coating thickness on non-metals?

Accepted Answer

The ultrasonic pulse-echo technique is used to measure the thickness of coatings on non-metal substrates (plastic, wood, concrete, and composites) without damaging the coating. Ultrasonic coating thickness gages (e.g. PosiTector 200) emit a high frequency sound pulse that travels into the coating via a coupling gel and reflects from ANY surface that is different in density.

Coating thickness readings are obtained by measuring the time taken for the ultrasonic signal to propagate from the probe to the coating/substrate interface and back. The travel time is divided by two and multiplied by the velocity of sound in the coating to obtain the thickness of the coating.

Question 2

Do your instruments require any formal training for use? Do you offer ‘demo’ models?

Accepted Answer

No. Our instruments are designed for simple operation, feature easy-to-use menus, both full and quick instruction manuals, and helpful videos. In lieu of demonstration models, we provide unlimited technical support via telephone and/or email, and a limited 30-day money back guarantee.

Question 3

Is the PosiTector 200 calibrated at the factory?

Accepted Answer

The PosiTector 200 arrives fully calibrated and ready to measure. A Long-Form Certificate of Calibration traceable to NIST or PTB is included, which documents actual readings taken by your instrument at our calibration laboratory on standards traceable to a national metrology institute. Beware of ‘Certificates’ or ‘Certificates of Conformance’ offered by competitors. These typically do not include actual instrument readings, and are often insufficient to meet common quality requirements.

The PosiTector 200 is factory calibrated to measure most polymer coatings out of the box without calibration or adjustment. If required, a simple gage adjustment can be made to a coating sample of known thickness as close as possible in composition to the intended application. For best results, the thickness of the sample should be equal to or slightly greater than the maximum expected thickness of the coating to be measured.

Question 4

Can the PosiTector 200 be used to measure coatings on metal substrates?

Accepted Answer

In many cases, yes! However, the following should be noted:
Metal Substrate Thickness: Because sound travels through metals approximately three times faster than it travels through most protective coatings, substrate thickness will largely determine the suitability of a particular coating thickness application for the PosiTector 200.

Gage Adjustment: Adjustment to the PosiTector 200 gage’s Hi Range to eliminate unwanted metal substrate back-wall echoes is typically required for improved measurement repeatability. This process of adjustment is simplified through the use of the PosiTector 200 Advanced gage’s Graphics Mode. Although a PosiTector 200 Standard gage model has the capability to accurately measure single coat applications and a total coating system thickness of multi-layer applications, we strongly recommend the use of a PosiTector 200 Advanced gage model for measurement on metal substrates.

Single Coat Applications: A minimum coating thickness of 13µm (0.5 mil) on a flat metal substrate with a minimum thickness of 1.25mm (50 mils) is usually required.
Multi-Layer Applications – Total thickness: In many circumstances, the total thickness of a multi-layer coating system over metal can be reliably measured. As in single coat applications, a minimum total coating system coating thickness of 13µm (0.5 mil) on a flat metal substrate with a minimum thickness of 1.25mm (50 mils) is usually required. Individual layers: The PosiTector 200 will measure the thickness of individual layers when each layer is thicker than 125µm (5 mils) and the metal substrate is thicker than 6mm (0.25”). A greater difference in the acoustic characteristics of each layer results in a greater likelihood of accurate individual layer measurement. A PosiTector 6000 probe is generally recommended over a PosiTector 200 probe for measuring coating thickness on metal substrates because – Lower cost Larger selection of probes (none requiring the use of an ultrasonic couplant gel) Greater accuracy Unlike PosiTector 200 probes, adjustment is not required for most protective coating properties Fully conform to international standards for measuring coating thickness over metal

Question 5

What is couplant? Do I need to use it every time I take a reading?

Accepted Answer

Couplant is required for every reading in order to propagate ultrasound into the coating. Water is a suitable couplant for smooth coatings. Use the supplied glycol gel for rougher coatings.

Question 6

Can the PosiTector 200 measure coatings that contain particles or aggregate?

Accepted Answer

Broadcast epoxy, urethane mortar and other coating systems that contain aggregates or particulate inclusions (silica, quartz flake, concrete, etc.) will present a significant measurement challenge to our ultrasonic PosiTector 200 instrument. This is caused by the tendency of the solid particles to interfere with the ultrasonic impulse and typically results in unreliable thickness readings.

Question 7

How do I ‘Zero’ the PosiTector 200?

Accepted Answer

Unlike a magnetic or eddy-current principle gage, an uncoated substrate is not required to Zero the PosiTector 200. Instead, the probe is held in the air away from the substrate when the Zero is performed.

Question 8

How often should the PosiTector probe be recalibrated?

Accepted Answer

PosiTector probes include a Certificate of Calibration showing traceability to NIST or PTB included (Long Form) with each probe - with no expiry or end date. They have no shelf life, therefore the length of time in the field is not a good indicator for recalibration intervals. Many organizations with quality programs and recertification programs require annual recalibrations, and this is a good starting point for most users.

DeFelsko recommends that customers establish calibration intervals based upon their own experience and work environment. Based on our product knowledge, data and customer feedback, a one year calibration interval from the date the instrument was placed in service is a good starting point.

Defelsko PosiTector 200

Defelsko PosiTector 200

Defelsko PosiTector 200

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