Resources
DONGRU app
Connect your DONGRU instruments, capture readings and generate reports straight from your phone.
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Industry Applications
Automotive Paint Inspection: How a Coating Thickness Gauge Detects Putty, Repaint and Collision Repair
Automotive paint inspection uses an Fe/NFe dual-mode coating thickness gauge: it first auto-switches principle by substrate (steel or aluminium), then judges from the deviation…
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Industry Applications
Steel Structure Coating DFT Acceptance: From Spot Layout to the 80/20 Rule
Acceptance of steel structure protective coatings is governed by SSPC-PA 2-2022 for spot count and pass/fail rules, and by ASTM D7091-22 for instrument operation.…
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Measurement Principles
Optical Measurement Principles: What Transmittance, Haze and Gloss Actually Measure
Transmittance measures the share of visible light that passes through a material (VLT), haze measures the scattered fraction of that transmitted light, and gloss…
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Measurement Principles
Substrate Thickness, Curvature and Edges: Three Geometric Effects That Distort Readings
The geometry of the part changes the reading systematically: a substrate that is too thin pulls the reading low, curvature changes the coupling between…
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Measurement Principles
Resolution, Accuracy, Repeatability: Three Specifications People Constantly Confuse
Resolution is the smallest displayed step, accuracy is how far a reading can sit from the true value, and repeatability is how well repeated…
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Measurement Principles
Type 1 vs Type 2: Why Magnetic Pull-Off Gauges Are Obsolete
ASTM D7091-22 and SSPC-PA 2-2022 sort coating thickness gauges into two types: Type 1 magnetic pull-off and Type 2 electronic. Type 2 gauges read…
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Measurement Principles
Measuring Coating Thickness on Non-Metallic Substrates: ASTM D6132 and Ultrasound
Coatings on concrete, wood, plastic, glass and fibreglass cannot be measured by magnetic induction or eddy current; they require ultrasonic coating thickness measurement to…
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Measurement Principles
Echo-Echo Through-Coating Mode: Why You Do Not Have to Grind a Painted Pipe
Echo-Echo mode calculates wall thickness from the interval between successive back-wall echoes, automatically ignoring the coating on the surface. Painted, coated pipework and hulls…
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Measurement Principles
Ultrasonic Pulse-Echo Thickness Measurement: Sound Velocity × Time ÷ 2
An ultrasonic thickness gauge fires a sound pulse and times its round trip between the two surfaces of the part, converting that time with…
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Measurement Principles
Fe vs NFe vs Dual Mode: A Quick Guide to Substrate Identification
Choosing a principle comes down to one question: is the substrate ferromagnetic? If yes, use magnetic induction (Fe). If not, and the substrate is…
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Measurement Principles
Eddy Current Coating Thickness Measurement: Why It Only Works on Non-Ferrous Metal
Eddy current testing drives a high-frequency coil to induce eddy currents in a conductive substrate and derives non-conductive coating thickness from the change in…
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Measurement Principles
Magnetic Induction Coating Thickness Measurement: How a Magnetic Field Becomes a Number
Magnetic induction uses a probe to generate a low-frequency magnetic field and reads how the ferrous substrate responds to it, deriving the thickness of…