CEM DT-156 Digital Paint Coating Thickness Gauge Tester

1. Introduction

1.1 General Information

The CEM DT-156 coating thickness gauge is designed for non-destructive, fast, and precise coating thickness measurement. It operates on either the magnetic induction principle or the eddy current principle, depending on the type of probe used. The gauge can automatically select the appropriate principle or allow manual selection via the menu system.

This device conforms to the following industrial standards:

• GB/T 4956-1985
• GB/T 4957-1985
• JB/T 8393-1996
• JJG 889-95
• JJG 818-93

1.2 Application

The principal applications for the DT-156 lie in corrosion protection. It is ideal for manufacturers, customers, paint shops, electroplaters, and industries such as chemical, automotive, shipbuilding, and aircraft engineering. It is suitable for use in laboratory, workshop, and outdoor environments.

Figure 2: Scope of application for the DT-156, including car paint, rubber, paint, and enamel.

1.3 Description of the Gauge

The gauge measures coating thickness on steel substrates using the magnetic induction principle (Fe) and on non-ferrous metal substrates using the eddy current principle (NFe). Measurement values and user information are displayed on an LCD with backlight for easy reading in various lighting conditions.

Figure 3: Diagram illustrating the DT-156's ability to measure coatings on both magnetic (Fe) and non-magnetic (NFe) materials.

It offers two operating modes: DIRECT and GROUP mode. DIRECT mode is for quick, occasional measurements without saving individual readings but providing statistical analysis for up to 80 readings. GROUP mode allows measurement and storage of up to 400 readings across 4 groups, with individual calibration and statistical analysis.

2. Supply Schedule

The following items are included with your DT-156 Coating Thickness Gauge Tester:

• DT-156 Gauge
• Two AAA batteries
• Plastics carrying case
• Operating instructions (English)
• Calibration Iron substrate
• Calibration Aluminum substrate
• Precision Standard foils
• USB connecting cable
• CD with PC analysis software
• Gift box

3. Specifications

4. Components and Controls

Figure 4: Front and back view of the DT-156 with labeled components.

1. LCD display
2. Red key for OK/YES/MENU/SELECT function in menu mode
3. Up / Left Key
4. Power ON/OFF key
5. Blue key for ESC/NO/BACK function in menu mode, or backlight ON/OFF in working mode
6. Down / Right Key
7. Zero Calibration key
8. Battery cover
9. USB connecting port

5. Setup

5.1 Power Supply

The DT-156 operates on two AAA batteries. To check the battery charge, press the power key. If the LCD does not illuminate or switches off after about one second, replace the batteries immediately. Note that the gauge may provide faulty measurements if the battery voltage is too low.

5.2 Replacing the Battery

1. Place the gauge upside down on a suitable surface.
2. Remove the screws from the battery compartment using a cross-tip screwdriver.
3. Raise the lid of the compartment.
4. Remove the old batteries.
5. Insert new AAA batteries, ensuring correct anode and cathode positioning.
6. Close the lid and fasten with screws.

Figure 5: Back view of the DT-156, showing the battery compartment.

6. Operation

6.1 Menu System and Basic Settings

Press the Power ON/OFF key to turn on the gauge. It will start in measuring mode. To enter the MENU mode, press the red-bar button. The menu system allows configuration of various settings and viewing of statistics.

Menu Structure Overview:

• Statistic view: Average, Maximum, Minimum, Number, Standard Deviation (S.DEV)
• Options:
  • Measure mode (Single, Continuous)
  • Working mode (Direct, Group 1-4)
  • Used probe (AUTO, Fe, No Fe)
  • Unit settings (μm, mils, mm)
  • Backlight (ON, OFF)
  • LCD Statistic (Average, Maximum, Minimum, S.DEV)
  • Auto power off (Enable, Disable)
• Limit: Limit settings (High limit, Low limit), Delete limit
• Delete: Current data, All data, Group data
• Measurement view
• Calibration: Enable, Disable, Delete Zero N, Delete Zero F

6.2 Measuring Modes

The DT-156 offers two primary measuring modes:

• CONTINUOUS Mode: Provides a running display of readings without requiring the probe to be lifted between measurements. Readings are not accompanied by a beep and are automatically entered into the statistics program as long as memory is available.
• SINGLE Mode: Readings are accompanied by a beep. Other functionalities are similar to Continuous mode.

Additionally, there are two working modes:

• DIRECT Mode: Recommended for simple, quick, occasional measurements. It provides statistical analysis for up to 80 readings, but individual readings are not saved permanently. Statistical values are reset when the gauge powers off or switches to GROUP mode.
• GROUP Mode: Allows measurement and storage of up to 80 single readings and 5 statistical values per group (up to 4 groups, total 320 readings). Calibration and limit values can be set and stored individually for each group.

Figure 6: The DT-156 demonstrating its dual working mode for both magnetic and eddy current measurements.

6.3 Probe Operation Modes

The probe can operate in three modes:

• AUTO: The gauge automatically selects the working principle (magnetic induction for steel, eddy current for non-ferrous metals).
• Fe: The probe works in magnetic induction principle (for ferrous metals).
• No-Fe: The probe works in eddy current principle (for non-ferrous metals).

6.4 Unit Settings

You can switch between Metric units (μm, mm) and imperial units (mils). In "μm" mode, the unit will automatically switch to "mm" when the reading exceeds 850μm.

6.5 Backlight

The backlight can be turned ON or OFF via the MENU system or by pressing the blue-bar button once in working mode.

6.6 Auto Power Off

The gauge will automatically power off after approximately 3 minutes of inactivity. This feature can be enabled or disabled via the MENU system.

7. Calibration

Accurate calibration is crucial for precise measurements. The accuracy of the reading depends on how closely the calibration sample matches the product sample in terms of material, size, and curvature.

7.1 General Hints for Calibration

Before calibration, ensure the measuring point and probe tip are free from grease, oil, or metal scraps. Even slight impurities can affect measurements.

7.2 Calibration Methods

There are four different methods available:

• Basic Calibration: Recommended for measurements on even surfaces with material, size, and curvature similar to the zero plate.
• Zero-point Calibration: Recommended if measurement errors up to ±(3% of reading + constant probe error) are acceptable.
• One-point Calibration: Recommended if expected readings are close to the calibration value and the permitted probe error is max. ±(1%...3% of reading + constant probe error).
• Two-point Calibration: Recommended for measurements on rough surfaces or for precise measurements on smooth surfaces where the expected thickness lies between two calibration foils.

7.3 Performing Zero-point Calibration

1. Switch on the gauge, ensuring it is at least 10cm away from any metal.
2. Place the probe vertically and rapidly on an uncoated sample (zero coating thickness).
3. The LCD will display the measurement. Lift the probe rapidly (at least 10cm from metal substrate).
4. Press and hold the ZERO button for about 1.5 seconds until the LCD displays "0.0 μm". The calibration is complete.
5. Repeat this procedure several times. The gauge saves the mean value of the previous calibration point.

Figure 7: Performing zero-point calibration on the DT-156.

7.4 Storing Calibration Values

Calibration values are stored in memory until changed. If an incorrect reading or command is entered, or if the gauge switches off, the calibration procedure should be restarted.

8. Limit Function

The DT-156 allows you to set high and low limits for measurements in both DIRECT and GROUP modes. Any reading that falls outside these set tolerance limits will trigger a warning indication:

• H: Reading above the high limit.
• L: Reading below the low limit.

Limit values are set via the MENU system.

Figure 8: The DT-156 displaying the limit alarm function.

9. Measurement Using Statistics

The gauge calculates statistics from a maximum of 80 readings in DIRECT mode, and up to 400 readings across 4 groups in GROUP mode. The following statistical values are calculated:

• NO.: Number of readings in Work Mode.
• AVG: Average value.
• S.DEV: Standard deviation.
• MAX: Maximum reading.
• MIN: Minimum reading.

In GROUP mode, if the storage capacity is exceeded, statistics will not be updated, but measurement can continue. If the memory is full, subsequent readings will be omitted from the statistics and marked with "FULL" in the LCD. In DIRECT mode, if the memory is full, the newest reading replaces the oldest, and statistics are updated.

10. Data Processing

All measurement readings from all work modes can be downloaded to a PC via the USB port for data analysis. Refer to the provided software guide for detailed instructions on using the PC analysis software.

11. Troubleshooting

The following list of error messages explains how to identify and eliminate common faults:

• Err1, Err2, Err3: Indicates a probe connection fault or deviant signal.
• Err1: Specifically for Eddy current probe issues.
• Err2: Specifically for Magnetic induction probe issues.
• Err3: Indicates issues with both probes.
• Err4, 5, 6: Reserved for future use.
• Err7: Thickness fault.

12. Maintenance

To ensure accurate readings and prolong the life of your DT-156, keep the probe tip and measuring surfaces clean. Regularly check for and remove any grease, oil, or metal scraps from the probe tip. Store the device in its carrying case when not in use.

13. User Tips

• Always perform a zero-point calibration before critical measurements to ensure accuracy.
• For best results, especially on uneven surfaces, utilize the two-point calibration method.
• Keep the probe and measuring surface clean to avoid distorted readings.
• When taking multiple readings, use the statistics function to get a reliable average.

14. Warranty and Support

The CEM DT-156 Coating Thickness Gauge Tester comes with a one-year guarantee from the date of purchase. For technical support or warranty claims, please contact your vendor.

This product is CE certified, indicating compliance with European safety, health, and environmental protection requirements.

Figure 9: Example of CEM certifications, including CE.

15. Company Introduction Video

Learn more about CEM and their commitment to precision measurement: