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GAOTek Coating Thickness Gauge with Wide Measure Range (Accurate)
GAOTek Coating Thickness Gauge with Wide Measure Range (Accurate)

Coating Thickness Gauge with Wide Measure Range (Accurate)

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GAOTek Coating Thickness Gauge with Wide Measure Range (Accurate) of 0.047 in to 8.85 in (1.2 mm to 225 mm) and is designed to measure ultrasonic conductors such as glass, ceramic, metal, plastic etc. Auto power off mode, coupling status indication, low battery indication and auto linear compensation are some of its important features. The device has a special memory that retains its settings even when the power is off. It adopts the ultrasonic measuring principle and provides an accurate and fast measurement of thickness for industrial materials.

Key Features

  • Auto calibration to assure the accuracy
  • Advanced auto linear compensation software program enhances the precision by correcting the non-linear accuracy of transducer
  • 10 thickness measurement storage and recall function available, which facilitates the height work or working in wild area
  • Sound velocity measurement with a given thickness by a sample hardware to measure the sound velocity, which avoids the further conversion or consultation of the table
  • Advanced memory that retains all of its settings even when the power is off
  • Auto power off mode designed to conserve battery life
  • Low battery indication
  • Use “up arrow” and “down arrow” keys to make a quick adjustment for the sound velocity/thickness and a quick recall to the stored data
  • Provides coupling status indication
  • Adjustable 12 sound velocities for different materials

Technical Specifications

Measuring Range 0.047 in to 8.85 in (1.2 mm to 225 mm) (steel)
Accuracy ± (1% H + 0.1) mm
Display 4-digital LCD display
Minimum Display Unit 0.003 in (0.1 mm)
Minimum Limit for Tube Measuring Ф 0.78 in x 0.11 in (20 mm x 3 mm) (steel)
Sound Velocity Range 1000 m/s to 9999 m/s
Working Frequency 5 MHz
Power Supply 3 V x 1.5 V AAA alkaline batteries
Operating Current Normal operation ≤ 50 mA
Backlight on ≤ 120 mA
Stand-by current ≤ 20 µA
Sound Velocity with a Given Thickness Range 1000 m/s to 9999 m/s
Size 2.83 in x 5.74 in x 1.14 in (72 mm x 146 mm x 29 mm)
Weight 0.44 lbs (202 g)
Operating Temperature 32 °F to 104 °F (0 °C to 40 °C)

Additional Information

Parts Description

LCD Diagram

Keypad Diagram

Operation Condition

  1. Operation area condition: For areas that are equal or bigger than the area, this unit is suitable for measurement. To measure the slim parts axially that is not vertical to the surface, the area shall not be too small, and if it’s small error will be shown.
  2. Curved surface condition: When the material is curved surface like boiler wall or tubing, the curvature radius must be more than or equal to39 in (10 mm), and the wall thickness must be more than or equal to 0.11 in (3 mm).
  3. Roughness condition: This gauge wildly applies upon the rough hardware/material, for most cases, the company’s provided transducer can make an exact measurement. However, if the roughness is too big due to the rust etc. the error measure may happen, in such case, please try to minimize the roughness or select the 2.5 MHz transducer (optional accessories).
  4. Working temperature condition: Material thickness and sound velocity will change along with temperature. In a normal measurement, environment temperature impact can be The transducer is made of propylene material, considering the protection of the transducer and its precision we recommend that the surface temperature of the hardware/workpiece should not be over 60, otherwise the transducer cannot put into use.

Operation temperature: 32 °F to 104 °F (0 °C to 40 °C)

Relative humidity: < 90% RH

Hardware/workpiece/material temperature: < 140 °F (60 °C)

Do not apply in violent vibration/erosive material. Avoid impact and humidity.

Operation Instruction

Before measurement

  • Connect the transducer with the main unit, press to turn on, LCD displays full screen for 0.5 seconds with back light, then icon will keep scanning with figure testing in 2 times. After that, LCD displays the last applied sound velocity with the registered memory unit, indicating the gauge is ready for use.

  • Sound velocity adjustment and revision – Press VEL to enter sound velocity adjustment, press or to select your desired velocity (There are 12 velocities stored in this unit). If you need to customize the sound velocity, during the adjustment press VEL again to enter velocity revision, while pressing or to revise the velocity, VEL and m/s icon will keep blinking. Press VEL to confirm and save the revised velocity, the unit will go back to normal status.


A calibration should be made for every replacement of transducer or batteries, this operation is sufficiently important to assure the measuring precision. If necessary, this step should be repeated when the accuracy is critical. Before calibration, put few provided coupling agent on the standard sample block to couple the transducer and the sample block. Press CAL to enter calibration mode, the vertical bar will keep scanning with CAL, VEL, m/s display, until the LCD displays 0.15 in (4.0 mm) indicating the calibration is completed. After calibration, sound velocity will back to your selected value, and ready to measure.

Thickness measurement

Put the coupling agent on the area to be measured to couple the transducer with the hardware/workpiece, LCD will display the thickness reading.

Sound velocity measurement

With a given thickness to read out sound velocity of material: Obtain the thickness of material by using Vernier caliper/micrometer, then couple the transducer with that sample material until a reading displays on the LCD, remove the transducer and press or to adjust the reading to match the thickness by caliper/micro meter, then press VEL to display the sound velocity and save in current sound velocity memory unit.

Data storage

  • Keep pressing STORE for 2 seconds to enter the data store mode, LCD display THICKNESS, mm, M icon with the first memory unit. If the first memory unit is not being registered, so LCD will display 0.0.
  • Press or to select your desired memory unit (1-10).
  • After picking up the memory unit, the new measurement will renew the memory unit, when the measurement completed the last reading will be stored in the selected memory unit.

Review the saved data

In normal status, press STORE for 2 seconds to enter into review data mode, press or to display saved data orderly. Press STORE to exit the review mode and back to normal status.

Low battery indication

When icon flashes, please replace the batteries for further measurement.

LCD back light and automatic power off

Before turn on the gauge, hold pressing CAL, and press button to turn on, the back light will be activated every operation will turn on the back light for 7 seconds. This unit will be turned off automatically in 2 minutes without any operation.

Measurement Tips

  • Cleaning surface – Before measuring, the dust, dirt, rusting and grease etc. that adheres on the hardware/workpiece must be removed off and cleaned.
  • Decreasing the roughness of surface – Too rough surface may result in measure error/fault reading. Please try to make the surface smooth by milling, polishing, filling or using high viscosity coupling agent.
  • Rough machining surface – The regular tiny texture/slots resulting from rough machining process may cause error, and the compensation method is the same as in the above point, adjusting the angle between the crosstalk segregating board of the transducer a metal membrane crossing the detector bottom center and linear texture/slots (parallel or vertically) may also get a better result.
  • Measuring pipe and tubing – When measuring cylindrical parts to determine the thickness of the pipe wall, an orientation of the transducers is important. If the diameter of the pipe is large than approximately 4 in, measurements should be made with the transducer oriented so that the gap in the wear face is perpendicular (at the right angle) to the long axis of the pipe. For smaller pipe diameters, two measurements should be performed, one with the wear face gap perpendicular, another with the gap parallel to the long axis of the pipe. The smaller of the two displayed values should then be taken as the thickness at that point.
  • Complex shape material – For complex shape material measurement, please refer to the above point, the smaller of the two reading should then be taken as the thickness.
  • Non-parallel surface – To get a satisfying ultrasonic response, the surface must have its one measuring side parallel with another, otherwise, you will obtain the wrong result.
  • Influence of the material temperature – The size and sound velocity of material will change with the temperature when the precision is critical, please make the measurement in 2 samples of the material under the same temperature to determine the proper reading resulting from the temperature. When taking the measurement for steel parts in high temperature, this method may be adopted to obtain the correct reading.
  • High acoustic reduction material – For materials in fiber, proliferous or big granular, acoustic dispersion will cause the energy attenuation that may result in abnormal readings (practically the reading less than the actual thickness), in this case, the material is not suitable for the gauge.
  • Reference sample block – For calibration for the gauge, a given thickness or sound velocity of the material is very important. Calibration needs at least one referring standard sample block. This gauge is provided with a 15 in (4.0 mm) sample block on the front cabinet, please see for calibration operations.

In different material and situation, only one sample block may not satisfy every calibration. The more similar sample block, the more exact reading is obtained. Ideally, referring block is a group of different thickness and same material, by calibrating to the referring block, the effect of variation of sound velocity will be minimized. To get the most exact measure, a set of referring block is very important.

In most situations, using one referring block will get a satisfying measurement. This referring block must be the same material with the same thickness as the parts to be tested. The referring block should be read out the thickness by the micrometer.

When measuring thin material which thickness close to the minimum limit range of this unit, please use a referring block to define an exact limit of this material (0.04 in (1.2 mm) for steel material). Do not measure the material of which the thickness is under the minimum limit.

When the material is a complex alloy in a large size, block that has a similar thickness with the material should be selected for calibration.

For most hardware by forging/casting, they have different inner structure, so that the sound velocity is slightly different. To reach the exact reading, the referring block has the similar structure as the hardware.

In comment measurement, you check the sound velocity on the table given in this manual instead of taking calibration for the referring block. However, this table is just for reference, sometimes the sound velocity will be different caused by different physical/chemical factors. The sound velocity of mild steel is adopted on the reference table.

Precautions for Accuracy

  • For very thin material – Any ultrasonic thickness gauge, when the thickness of the material to be measured is less than the minimum limit the fault reading will occur. Using sample block compare method to get a minimum limit of this material. In measuring the thin material, an error may happen that the reading is two times as the actual dimension. Another error which displays the reading much bigger than the actual. To prevent the wrong reading, double check out the minimum limit in the thin material.
  • For stained, rusting surface – The stained/rusting surface on the contra side will occur wrong readings. Sometimes a small stained spot is hard to find out. Take care for measurement while measuring the known through sting spot/suspicious area. Or using sound insulation board Celotex to locate the spot in different testing angles.
  • Identify different velocity with the various material – A fault reading would obtain when measuring the hardware with the velocity calibrated by the prior material. So a correct velocity should be adopted. The fault reading may also result from the difference between the actual velocities with the calibrated value.
  • Abrasion for the transducer – Because the transducer is made of propylene, long period use will cause the surface of transducer to become rougher which will decline the sensitivity and lead to the wrong reading. Please polish the surface with sand paper or whetstone to assure the smoothness. If the reading is still unsteady, the transducer should be replaced with new one.
  • CAL function – CAL (calibration) is used to calibrate the unit with the standard block on the panel, do press this key for calibration with other materials or the wrong measuring will take place.
  • Multilayer/composite material – It is impossible to read out the thickness of the uncoupled multilayer for the ultrasonic wave cannot go through the uncoupled space. Furthermore, the sonic wave cannot travel in the composite material at an even speed, so ultrasonic reflect principle cannot be applied for measuring the multilayer/composite material.
  • Influence from the oxidized surface – For some metals such as aluminum, a layer of oxide is being generated on their surface. The oxidized layer combines with the substrate tightly, but the sonic wave travels within 2 different materials which will lead to error reading, the more oxidized layer the reading will be more tolerant. Please calibrate the unit with the sample block that picks up along the hardware to be measured, and obtain the thickness of sample block by using micrometer/caliber.
  • Abnormal reading – A seasoned operator should be capable to distinguish the abnormal reading, practically result from rusting, erosive recess surface/incorrect calibrate sample block/the inner flaw of material.
  • Choosing and using coupling agent – Coupling agent serves the high-frequency ultrasonic wave transmitting between the transducer to the hardware. Choosing incorrect agent or wrong operation may cause error or poor coupling which lead to failure of measuring. The coupling agent should be used in proper way, typically, a single droplet of the agent is sufficient.

It is important to use a proper coupling agent, low viscosity agent (the provided agent/machining oil) is suitable for a smooth surface. For rough/vertical /aluminum surface, high viscosity agent like glycerin and lubrication grease is applicable.


  • Battery replacement – When low battery icon is showed, please replace the batteries.
  1. Press to turn off.
  2. Open the battery door properly.
  3. Replace the low power batteries by new batteries in correct polarity.
  4. When the gauge is not used for a long time, please take out the batteries.
  • Protection of transducer – The wear face of the transducer is propylene material which is easy to be scratched. While taking the measurement on a rough material, please use the transducer in gentle motion.

The temperature of the hardware should not be over 140 °F (60 °C), otherwise, it will cause damage on the transducer.

Adhering oil, dust on the wear face will speed up aging of the transducer and lead to rupture. Clean the lead-wire and transducer after use.

  • Cleaning the cabinet – Do not use solvent/alcohol for cleaning which erodes the cabinet and LCD window. Brush and sweep only with a moist cotton cloth.
  • Cleaning the sample block – The coupling agent should be put on the sample block during calibration. After using the sample block, it should be cleaned for preventing rust. In higher temperature environment, be sure to protect the block from the droplet of water. If the gauge is not in use for a long period, please apply some anti-rust on the sample block.
  • Avoid shocking/impact. Do not store the unit in high humidity environment.

Sound Velocities of Common Materials

Material Velocity (m/s) Material Velocity (m/s)
Aluminum 6320 Acetate resin 2670
Zinc 4170 Phosphor bronze 3530
Silver 3600 Turpentine 4430
Gold 3240 Glass 5440
Tin 3230 Incoloy alloy 5720
Iron/Steel 5900 Magnesium 6310
Brass 4640 Monel alloy 6020
Copper 4700 Nickle 5630
SUS 5790 Steel 4330 (mild) 5850
Acrylic resin 2730 Steel 330 5660
Water (68 °F, 20 °C) 1480 Titanium 6070
Glycerin 1920 Zirconium 4650
Soluble Glass 2350 Nylon 2620

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