Basic Info.
Standard
Celsius/Fahrenheit
Origin
Beijing, China (Mainland)
Product Description
Digital high precision crack depth measuring instrumentHMG SERIES Crack Depth GaugeUsed in the equipment maintenance of the operating system -- for the equipment parts with cracks, the development status of cracks can be mastered through regular inspection, and the timely and economical repair or update time can be determined to ensure the safety of the system.Used in the quality control of the manufacturing process -- for the work piece with cracks in the processing process, the repair and rescue measures can be formulated or decided according to the crack depth measurement results and the manufacturing process standard requirements.Host size: handheld model: 180x100x43mm, Portable model: 67x148x190mmStandard probe: φ19x130 mm, replaceable gold-plated probeQuality: less than 1kg (including built-in rechargeable battery)Handheld HMG - P12 Performance FeaturesLightweight portable size and ordinary digital multi meter similar, weight less than 1Kg (include rechargeable batteries).Excellent performance is nondestructive to the part under test. High reliability of measurement data. Resistance to the environmentStrong interference ability. With zero automatic correction function.The continuous working time of dc power supply is long and the site is easy to use.Simple operation intelligent operation, easy to master, the number display intuitive and simple.Single row probe placement method Single row probe placement Crack block Double-row probe placement method The main parametersScope of application: surface crack depth measurement of conductive materialsWorking principle: combination of ac potential method and computer technologyPower source: built-in rechargeable NiMH batteryPower adaptor: input: AC 220V/50Hz current:DC 800mAWorking hours: continuous use for 12 hoursMeasuring range: ferromagnetic material 0 -- 100mmMeasurement accuracy: the relative error is no more than 10% at full rangeResolution: not less than 0.1mmThis instrument does not need the user to carry on the numerical calibration.The random vertical crack test block is used to check whether the instrument is in normal working state, not used to calibrate the test block. When the relative error between the instrument reading and the nominal depth of the specimen is less than 10%, the instrument is in normal working condition Very short cracks can also be measured Surfaces with a small radius of curvature can also adaptMethod of measurementThe operation method is to cross the probe on both sides of the crack and perpendicular to the measured surfacePress down the probe and read the measurement data directly on the LCD display screen of the host computer.Probe selectionStandard type according to the different arrangement of 4 probes, standard probeIt can be divided into two types: single-column type and double-column type.Special probe can be customized according to different engineering application occasions and special requirements of the tested object.Excellent quality imported precision devices, advanced manufacturing technology, excellent quality and reliable.Widely used in machinery manufacturing, petrochemical, aerospace, nuclear power and other industrial fields in non-destructive testing.There are standard models for conventional measurement and customized models for special conditionProvide technical support for difficult problems in engineering measurement, and carry out special research on the measurement requirements of special working conditions.Operation:- Power on the gauge
Press the power button after confirming that the main engine is firmly connected to the probe. Do not plug or unplug the probe with power on! Press the POWER button of the main engine, and the red indicator POWER ON will prompt the POWER to be connected, and the LCD screen of the main engine will display 00.00 later, and the main engine will begin to work after a little preheating. If the yellow indicator light is LOW BAT, or the LCD screen is dim and flickering, it indicates that the battery pack is short of power, and when the voltage is too LOW, there will be a continuous "wow... "Prompt sound, please shut down the power supply of the main engine in time and start working after charging the battery. See 4.1 charging instructions for charging methods.- Initial value measurement
The initial measurement value is recorded at the crack - free part.Method: hold the probe, press down the probe near the crack under test with no smooth defect, and pay attention to the uniform force, so that all the four probes have a stable and reliable elastic contact with the surface under test.If the initial measurement is between 0 and 2.0mm, the initial reading is simply subtracted from the subsequent crack depth measurements. Subsequent operations can skip 5.5 and 5.6 and directly enter 5.7 measurement steps.If the initial value is greater than 2.0mm, see 5.5.Tips!!!!! When the probe is moved on the part under test, the probe must be separated from the part under test to avoid bending the probe.5.5 Customization of user materialsIf the initial display value is large when measuring the crack free part under test, it indicates that the material characteristic of the current workpiece is greatly different from the default material characteristic of the instrument, and user material customization is required.Operation method:1) press the host custom button CAL.2) press down the probe near the crack under test and remove the probe after hearing the sound of "di". "CAL" appears on the display. Repeat the measurement at the same position for several times (at least 3 times).3) press the button CAL again to make it pop up.4) press the MAT button, press the probe again in the same position, hold for 5 to 10 seconds, remove the probe after hearing the sound of "di", observe the display screen, the display value changes to 000.0 or 000.1, then the custom operation of material is completed.5.6 Selection of user materialsAfter the user-defined material is complete, there are two options for continuing the crack depth measurement. One is the default material mode, when the material selection button MAT is in the unpressed state; Second, enter the user's material mode for measurement, and press MAT button. The crack depth value measured is customized for the current user's material.5.7 MeasurementMethod of measurement1) hold the probe and place the probe.When using the single-row probe to measure, two probes are placed on both sides of the crack. For the double-row probe, the two red circular pit striding marks should be aligned with the direction of the measured crack on the surface. The probes on both sides of the line should be placed on both sides of the crack. See figure 5.2) Press down the probe perpendicular to the measured surface, and pay attention to the uniform force, so that the four probes have smooth and reliable elastic contact with the measured surface. The sound of "di" indicates that the measurement is effective and the probe can be removed. At this time, the number on the LCD screen is the crack depth value (mm) at the measured position.Tip!!!!! The crack width had a slight effect on the measured results but could not exceed the distance between two adjacent probes.5.8 record readingIn order to obtain stable test results, each measurement point should be measured at least 3 times, and each measurement value should be recorded to obtain the average.In the measurement process, the display value of the last time has no influence on the next measurement result, so it does not need to clear the screen.5.9 Power on the gauge if not use.5.10 Inclined crack measurement methodAt present, the common methods of nondestructive testing to determine the surface crack depth of materials are based on the assumption that the defect is perpendicular to the surface. In fact, the orientation of some surface defects in the metal is not completely perpendicular to the surface, but has a certain inclination Angle. After determining the inclined direction and Angle of the crack, the depth of the crack from the surface can be determined by simple calculation. As shown in FIG. 9, crack dip Angle and crack penetration depth D were obtained by measurement, and crack depth D was obtained by calculation. FIG.9 Where d -- crack depth;D -- crack invasion length;-- the Angle between the crack and the surface.When = PI /2 (the crack is perpendicular to the surface of the workpiece).When the four electrodes are arranged in a straight line, the probes are placed on both sides of the crack (close to the crack edge and parallel to the crack, see figure 10). If the crack is inclined to one side, there will be a difference in the two potential differences, and the crack will be inclined to the side with a large potential difference. Accordingly, the inclined direction and inclination Angle of the crack can be determined.Method of measurementStep 1: determine whether the crack is inclinedThe probe was placed on the left side of the crack, and the pressure was applied to make the probe perpendicular to the measured plane to ensure a good contact between the probe and the measured part. The probe was as close to the crack as possible and parallel to the edge of the crack, as shown in FIG. 10-11. Then the probe was placed on the right side of the crack, and the pressure was applied to make the probe perpendicular to the measured plane, so as to ensure a good contact between the probe and the measured part, and as close as possible to the crack and parallel to the edge of the crack. Continuous measurements were made several times, and the numerical values were recorded. If the two measurements are the same or close, the direction of crack invasion is perpendicular to the surface. If the difference between the two measurements is large, it indicates the direction of crack invasion and the surface inclination. The crack inclination Angle is determined according to the following steps.FIG.10Step 2: crack inclination Angle measurement Left side crack measurement Right side crack measurement1) press OBL on the operation panel of the host machine.2) four probes in the probe, near the crack on the left side of the pressure, the LCD display "with", should make the probe and measured perpendicular to the plane, and make a probe against crack, can ensure good contact probe and measured, and as far as possible close to the crack, the attachment between the probe and crack parallel to the edge as far as possible, as shown in figure 10 V1 measuring position. After continuous measurement, press the "AVE" button and the LCD will display "End1".Attention!!!!! Do not let any probe fall into the crack opening line or cross the other side of the crack. All 4 probes must be on the left edge of the crack.3) place the probe of the four probes placed near the crack on the right side, under pressure, LCD display "with", should make the probe and measured perpendicular to the plane, and make a probe to crack, can ensure good contact probe and measured, and as far as possible close to the crack, the attachment between the probe parallel with the edge of the crack as far as possible, as shown in figure 10 V2 measuring position. After several continuous measurements, press the confirmation button AVE, and the display screen will display the crack inclination Angle "xx0".Attention!!!!! Do not let any of the probes fall into the crack opening line or across the other side of the crack. All four probes must be on the right edge of the crack.Step 3: determine the crack invasion lengthCrack depth was determined in accordance with the standard crack depth measurement method (see 5.1 -- 5.8), i.e., invasion length D.Step 4: crack depth calculationAccording to the measured crack inclination Angle and crack invasion length D, the crack depth D can be calculated by using formula (1), as shown in figure 9.Factors related to crack depth measurement accuracyUnder some specific conditions, the measured value of the instrument cannot accurately reflect the real depth of the measured crack, so the operator should pay attention to and make a correct judgment. Generally, the following physical factors affecting the measurement accuracy need to be considered.6.1 surface condition of the object under testThe workpiece surface under test should be clean and smooth to ensure good and stable electrical contact, as fluctuations in contact resistance may lead to incorrect measurement results.6.2 edge effectIf the crack under test is perpendicular to an edge, note that the probe is placed at least twice as far from the edge as indicated by the edge crack depth measurements.However, the depth of the crack at the edge of the workpiece is usually unknown. For example, if the crack depth is shown to be a certain value when measured at the edge, then the correct measurement result can be obtained by placing a probe beyond the value at the edge.If the crack is parallel to the workpiece edge, even if the crack is close to the edge, the measurement error caused by the edge effect need not be considered.6.3 deep cracks on workpiece with finite thicknessIf the actual crack depth is close to the workpiece thickness, the measured value will be greater than the crack depth. In this case, the current will be blocked by the bottom surface of the crack and cause a large potential drop. This effect is negligible when the crack depth is less than 90% of the workpiece thickness.6.4 short fatigue cracksAccording to the measurement principle of potential method, the length of crack is generally required to be greater than three times its depth. In practice, most cracks meet this condition. However, some cracks may be as long as they are deep (for example, an arc-pit crack), in which case the measured value is 10-20% smaller than the actual depth of the crack because a portion of the current does not flow under the crack but circumvents the surface.6.5 crack widthAn important feature of the potential method is that the crack width does not affect the measurement of the crack depth because the current path between the two electrodes of the probe is independent of the crack width. Of course, the crack width cannot be greater than the distance between the two measuring probes.6.6 multi-crack distributionThe non-continuous distribution of cracks in the workpiece will affect the measurement accuracy. In some cases, there is a metal contact zone between the two side walls of the crack in the depth direction. This kind of crack is actually composed of several continuous crack sections. See figure 12. In this case, only the topmost crack depth can be measured because the current causes a short circuit in a continuous place, so that the reading does not represent the actual crack depth D, but the crack depth D closer to the surface. Therefore, in the crack depth measurement, the continuity of the crack itself is the premise to ensure the high precision measurement. Because the current always flows along the path of least resistance, that is, over the first metal contact bridge. This type of crack is often FIG.126.7 material heterogeneityThe inhomogeneity of material structure has a certain influence on the measurement, because the inhomogeneity of material directly causes the change of measured value. However, the general measurement area is not too large, so this effect can be ignored.7. Troubleshooting of common problemsProblem 1: when the crack depth is measured, only 000:0 is displayed on the display screen.If it still shows only 000:0, it means that the probe is not connected to the main machine. Please turn off the power supply of the main machine and carefully check whether the interfaces between the main machine and the probe are firmly connected. Tighten loose or detached joints.If the measurement is normal on the test block, the reason is that the conductivity of the measured material is too different from the measuring range of the instrument. If this kind of material needs to be measured regularly, please give your instrument to the distribution unit to reset the measuring range of the conductivity.Question 2: during the measurement, the display value of the measurement remains unchanged.The reason is that the trigger device is temporarily locked, and the probe is repeatedly pressed down and raised several times in any part of the part under test, and the number on the display screen can jump. If it still doesn't work, turn off the power and turn it back on.Problem 3: the number on the display screen is dim, the measured value is unstable, or there is no display.The reason is that the battery power is insufficient. Please turn off the power supply of the host computer to charge the battery.8. Principle of ac potential methodWhen the current passes through the test part, a certain current and potential field will be formed. If there is a crack on the workpiece surface, the effect on the current potential field will be different with the different shape, size and size of the crack. The method of measuring potential distribution is used to judge the condition of crack in metal material.FIG. 2 shows the current and potential fields of four current electrodes (or current probes) arranged in a straight line respectively at the crack free part (a) and crack free part (b) of the workpiece. A constant current through current probes A and B generates A current field in the workpiece and A potential distribution related to the composition and structural characteristics of the material. The potential difference between A certain point can be detected through another pair of electrodes c and d and displayed on the voltmeter. It is assumed that the influencing factors and geometric dimensions related to the material are the same, and the same current is used to test the samples without cracks and with cracks respectively. Obviously, the difference between the potential difference between the samples without cracks and the potential difference between the samples with cracks between the measured poles c and d is caused by cracks. If the test current, material and thickness of the workpiece under test remain unchanged, and only when the crack depth changes, the potential difference is a function of the crack depth. Through numerical analysis and calibration, the potential difference signal obtained by the electrical measurement system can be converted into the crack size, so as to measure the crack depth.The current used in the potential detection method is dc and ac, dc method has the advantages of simple equipment, no ac signal interference, the disadvantage is that the impact of thermoelectric emf is large, generally only used for point measurement. The ac potential method can not only overcome the influence of thermoelectric emfs, but also be used in production inspection. In addition to point measurement, continuous measurement, recording and automatic marking can also be realized. HMG series crack sounder adopts ac potential method; A frequency selective amplifier with low noise and high amplification ratio is designed to eliminate the external electromagnetic interference and ensure high measurement accuracy. The power supply is powered by high-energy batteries, which is convenient for field use. PC communication interface preset, according to user needs for functional expansion.
Address:
E506, Power Creative Building, No. 1 Shangdi East Road, Haidian District, Beijing, China
Business Type:
Manufacturer/Factory
Business Range:
Industrial Equipment & Components, Instruments & Meters, Tools & Hardware
Management System Certification:
ISO 9001
Company Introduction:
Mitech is a manufacturer specializes in Non-Destructive Testing (NDT) instruments. Located in Beijing, Mitech has a professional engineer team devoted in R&D and manufacturing advanced high technical instrument; Its main products are ultrasonic digital flaw detectors, portable metal hardness testers, handle ultrasonic thickness gauges, and coat thickness gauges etc.
Until now, Mitech has distributors dispersed in major cities of China and offers excellent after-sale service. Mitech′s instruments are widely used in domestic generating industry, petroleum and chemical industry, pressure vessel manufacturing industry and so on, for providing quality control procedure; Customers are satisfied with the high-quality, good reliability and its prompt after-sale services.
Mitech′s mission is to provide customers with the best products and services, make contributions to the development of our world, the company is active in communicating with our distributors and customers both present and potential, main conversions and exhibitions of non-destructive testing are good chances for people to know more about Mitech and its products. Mitech welcomes to join hands with more friends.
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