MANUAL TT-220 TT-220
INDEX 1. GENERAL 2 1.1 Scope of applications 2 1.2 Basic working principle 2 1.3 Basic configuration TT220 2 1.4 Technical Parameters 3 1.5 Main functions 3 2. OPERATION OF GAUGE 4 2.1 Basic allocation (single / continue mode) 4 2.2 Measurement 5 2.3 Deletion of data 5 2.4 Statistics 6 3. CALIBRATION 7 3.1 Calibration standard 7 3.2 Calibration methods 7 3.2.1 Zero point calibration 7 3.2.2 Two points calibration 8 3.3 Basic calibration 8 4. INFLUENCING FACTORS 9 4.1 Description of influencing factors 9 4.2 Operating rules 10 5. MAINTENANCE AND REPAIR 11 5.1 Maintenance 11 5.2 Charging 11 5.3 Malfunction 11 5.4 Table of Error codes 12 Manual TT-220 1
1. GENERAL 1.1 SCOPE OF APPLICATION The thickness gauge TT220 can perform fast, non-destructive and precise measurement of thickness of non-magnetic coating on a magnetic metal base, e.g. aluminium, chromium, copper, enamel, rubber and paint-coating on steel, iron and non-austenic stainless steel base. The TT220 can be widely used for detection in the manufacturing industry, metal processing industry, chemical industry and inspection and testing of commodity. It is especially suitable for measurement in construction on-site. 1.2 BASIC PRINCIPLE The thickness gauge is based on the magnetic measuring method. Basic operating principle: When the probe comes into contact with the coating, the probe and magnetic metal base make up a closed magnetic circuit. As the existence of non-magnetic coating causes change of magnetic resistance of magnetic circuit, the thickness of coating can be calculated by measuring the change. 1.3 BASIC CONFIGURATION TT220 1) Basic configuration TT220 Standard specimen Standard base Charger 1 set 1 box 1 piece 1 set 2) Parts of thickness gauge. 1. Probe F1 integrated 2. Liquid crystal display screen 3. Up key: 4. Down Key: 5. Mode Key: MODE 6. Switch/clear Key: On/C 7. Charge socket 8. Spare socket 2 Manual TT-220
1.4 TECHNICAL PARAMETERS Model: Principle: Measuring range: Lower limit: TT220 magnetic induction 0-1250 microns 1 micron Accuracy (H= nominal value): zero-point calibration: ± (3%H)+1 micron two-point calibration: ± (1%-3%)H+1 micron Minimum radius workpiece: convex 1.5/concave 9 mm Minimum measuring area: Ø 7 mm Critical measuring thickness: 0.5 mm Operating temperature: 0-40 0 C Humidity max.: 75% Power supply: NiCd Battery 2 x 3.6 volt Dimensions: 150mm x 55.5mm x 23mm Weight: 150 gr. 1.5 MAIN FUNCTIONS 1) Zero point calibration and two points calibration 2) Five statistic data; average (MEAN), maximum (MAX), minimum (MIN), number of measurements (NO), standard deviation (S.DEV.). 3) Fifteen values can be obtained by means of statistical calculation. 4) Continuous measurement (CONTINUE) and single measurement (SINGLE) 5) Automatic switch off 6) Deletion: delete single/all data 7) Buzzing for next measurement 8) Indication of underpressure on probe 9) Error codes automatically on display Manual TT-220 3
2. OPERATION Before starting In order to acchieve accurate readings, the zero point calibration or two points calibration should be carried out for accurate measurement. See chapter 3. Indication of low voltage: If a sign flashes on the display after switching on or during the process of measurement, it means that the battery is almost empty. If the sign is stable, the batteries are completely down, and the gauge will automatically switch off. Recharge ± 12-14 hrs. 2.1 BASIC ALLOCATION The gauge works in two basic ways: normal measurement and basic calibration (only for special cases; see chapter 3). The normal measurement comprises: single measurement and continuous measurement. The switch-over of the above mentioned operating ways is called basic allocation and is performed during switching-on. If the gauge is already switched-on, the change of basic allocation must be carried out after automatic switching-off. 1) Normal switch-on: Press the on/c key. With a buzzing the gauge will show the results of the previous measurement Then the gauge enters into the mode of normal measurement without any change of the basic allocation. The display will show for example: 30 µm 2) Switch-on with change of basic allocation: The switch-over of the above mentioned operating ways is called basic allocation and is performed during switching-on. If the gauge is already switched-on, the change of basic allocation must be carried out after automatic switching-off. Note: It is allowed to change only one basic allocation each time. Press key: MODE + on/c + MODE Function on display: SINGLE or CONTINUE measurement mode. RESET? (this is no normal delete function!): If you DO NOT wish to RESET the gauge completely, then press any key seperately afterwards to return to the normal state If you DO want to RESET and Basis-calibrate the gauge then press all keys together: = MODE + on/c + + 4 Manual TT-220
Attention please!! Measuring after setting the gauge to B-Calibrate will delete former standard basic calibration! Perform the basic calibration only in these special cases: - When the tip of the probe is worn out - When it is used for special purposes If the error of measurement evidently exceeds the given limits, the characteristics of the probe have to be calculated again, which is called basic calibration. SEE CHAPTER 3! 2.2 MEASUREMENT Switch on the gauge Bring its probe perpendiculary in contact with the surface to be measured and press In the SINGLE-mode the display will now show a reading after buzzing. Lift the gauge away from the surface before carrying out the next measurement. (To renew the magnetic induction it is necessary to take the probe away from the surface). In the CONTINUE-mode the display will show continuously different readings without buzzing. Move the probe gently and with constant pressure over the surface to get an amount of readings. Statistics will show the exact number of readings etc. afterwards. Note: The continuous measurement is not applicable for calibration, calibrate in single mode. 2.3 DELETION 1) Single deletion: When there is a large error in the result of one measurement and you don't want the figure to enter into the statistical calculation, then press the MODE key and the gauge cues DEL ONE?. Then press the on/c key and this reading is deleted. (If you do not want to delete it, you can press the Up key A or Down Key V to return). MODE key > DEL ONE? >on/c> µm 2) Total deletion: If you want to delete all the data stored to renew the measurement, you can press the MODE key two times and the screen shows DEL ALL?. Then press the on/c key and all the stored data will be deleted. (If you don't want to delete them, you can press the Up key or Down Key to return them.) MODE key 2X> DELALL? >on/c> µm Manual TT-220 5
2.4 STATISTICS Repeat a measurement over 3 times, but not more than 15 times. Press the MODE key 3 times. The screen shows: MODE key 3x > DIS. STATS? (Display statistical values) Press Up key or Down Key The display will show successively for example: MEAN 100 µm (average value) NO. 5 (number of measurements) MAX 103 µm (maximum measured value) S. DE\1. 1.6 µm (standard deviation) MIN 99 µm (minimum measured value) If you want to return to the mode of measurement afterwards, press MODE key or on/c key again. Higher accuracy In order to raise the accuracy of the measurement, the measurement may be carried out at the measured point many times (but not more than 15 times) and gross errors may be deleted by means of the deleting function. The results will then be processed by using the statistical function and an accurate thickness of the coating will be obtained. 6 Manual TT-220
3. CALIBRATION In order to achieve an accurate measurement, the gauge must be calibrated. 3.1 CALIBRATION STANDARD A foil of known thickness or a test piece with coating of known thickness can be used as standard specimen for calibration, which is shortly called calibration standard. 1) Calibration foil For the foil is referred to as non-magnetic metal or non-metallic foil or gasket, which is suitable for calibration on curved surfaces. 2) Standard testplate / block with coating Uniform non-magnetic coating of known thickness firmly bonded to the testplate/block can be used as a calibration standard. 3) Substrate / base For the gauge, the magnetic conductivity and surface roughness of the substrate or base of the standard testblock should be similar to that of the measured workpiece. In order to verify suitability of the standard, a comparison of readings of measurement of the bases of standard testplate and workpiece must be carried out. 3.2 CALIBRATION METHODS Two methods of calibration are used. Zero point calibration Two points calibration In addition, there is a basic calibration for probe. (see paragraph 3.5) 3.2.1 ZERO POINT CALIBRATION Carry out one measurement on the base. The indication of the gauge is (X, Y mm). Press on/c key once. The screen shows (0.0 mm) or a higher value. The first zero calibration is fulfilled. In order to calibrate zero point precisely, it is necessary to repeat the above operations until the value (0.0 mm) is reached or a value very close to (0.0 mm). Repeat not more than 15 times. Otherwise an indication (E 07) will be shown as a cue. Measurements can be carried out after the zero point calibration is finished. 3.2.2 TWO POINTS CALIBRATION Calibrate the zero point as stated above. Carry out measurement on a standard foil or other specimen with a thickness approximately equal to that of the measured coating. The display shows (x, x mm). Manual TT-220 7
Press Up key or Down Key to correct the reading to make it equal to the nominal value. note: Even if the reading conforms to that of the standard specimen, it is absolutely necessary to press the Up key or Down Key both once to calibrate. If you want to more accurately carry out the two points calibration, you can repeat above operations to raise the accuracy of calibration and reduce accidental errors. Sand-blasted surface While the characteristics of the sand-blasted surface cause great deviation of measured value from the true value, the thickness of coating shall be determined in the following way: A. Calibrate the gauge on a smooth surface with the same radius of curvature and base in the way shown in paragraphs above. B. Carry out measurement on an uncoated and a surface that is sand-blasted in the same way about ten times. Get an average value Mo. C. Carry Out measurement on a coated surface ten times and get an average value Mm. D. The thickness of coating is (Mm-Mo) ±s. where s (standard deviation) is the larger of Mm and Mo. 3.3 RESET AFTER EMERGENCY AND BASIC CALIBRATION OF GAUGE This function shall not be used unless it is absolutely necessary! After automatic switch-off, press keys + MODE simultaneously to force the gauge to reset in case of malfunction or failure to switch on after charging. The basic calibration will be changed and the data will be lost in that case. As a result, the basic calibration has to be carried out again! Therefore the function shall not be used unless it s absolutely necessary. After RESET? has appeared on display: lf you DO NOT wish to RESET the gauge, then press any key (MODE or on/c or or ) seperately afterwards to return to the normal state If you DO want to RESET and Basis-calibrate the gauge then press all keys together: = MODE + on/c + +. Basic calibration is only necessary in the following cases: - When the tip of the probe is worn out - When the TT220 is used for a special purpose. If the error of measurement evidently exceeds the given limits, the characteristics of the probe must be calculated again, which is called basic calibration. The probe may be calibrated again by inputting 6 calibrating values: 1 zero value and 5 values of known thickness. How to handle (or send your gauge to your supplier for this procedure): After RESET? press all keys to enter into the mode of basic calibration: B-Calibrate Calibrate to zero value (see zero point calibration). Continuously repeat many times to get an average value of multiple calibrations so as to raise the accuracy of calibration. Carry out calibration of 5 increasing thicknesses using standard foils (see two points calibration). Repeat calibration for each thickness several times to raise the accuracy. Each thickness must be at least 1.6 times the preceding one, ideally two times, e.g. 50, 100, 200, 400, 800 microns. The maximum thickness should be near to but lower than the upper limit of the probe. After input of the 6 calibrating values, measure the zero point again. The gauge will now automatically switch off. Since the new calibrating values have already been stored in the gauge, it will work according to the new calibrating values when switched on. 8 Manual TT-220
4. INFLUENCING FACTORS The main factors influencing the accuracy of measurement of the gauge are magnetic conductivity of the base, thickness of the base, edge effect, curvature, deformation of test-specimen, roughness of surface, external magnetic field, adhering matters, pressure of probe, etc. 4.1 DESCRIPTION OF INFLUENCING FACTORS 1) Magnetism of base metal The magnetic measurement of thickness is influenced by variation of magnetism of the base metal (in actual application, the variation of magnetism of mild steel is considered insignificant). In order to avoid the influence of the cold working factor of heat-treatment, standard specimen with the same characteristics as the base metal of the test-specimen shall be used for calibration of the gauge. 2) Thickness of base-metal Each gauge has its critical minimal thickness of base-metal. For the TT220 this critical value is 0.5 mm. 3) Edge effect. The gauge is sensitive to abrupt change of the surface form of test-specimen. The measurement near to the edge or corner of the test-specimen is not reliable. 4) Curvature The curvature of test-specimen has influence upon the measurement, which increases with the reduction of the radius of the curvature. See technical parameters chapter 1. 5) Roughness of the surface The roughness of base-metal and coating has on influence on the measurement. The higher the roughness, the more influence. A rough surface can cause systematic error and accidental error. To overcome those errors, the number of times of measurement shall be increased in different positions. If the base-metal is rough, zero point calibration of the gauge must be carried out in several positions on the uncoated base-metal with similar roughness. 6) Magnetic field A high magnetic field generated by surrounding electric equipment seriously interferes with the magnetic measurement of the thickness. 7) Adhering matters The gauge is sensitie to the adhering matters, which are harmful for close contact with the probe and the surface of the coating. Therefore the adhering matters must be cleared away to ensure the direct contact of the probe and the surface of the measured test-specimen. 8) Pressure of probe The pressure applied by the probe to the test-specimen exerts influence on the reading of the measurement. Therefore a basically constant pressure of the probe is kept by a spring. 9) Direction of the probe The direction of the probe exerts influence on the measurement. The probe must be kept perpendicular to the surface of the test-specimen in the process of measurement. Manual TT-220 9
4.2 OPERATING MLES 1) Characteristics of the base-metal The magnetism and surface-roughness of the base-metal of the standard-specimen must be similar to those of the test-specimen. 2) Thickness of the bas~metal Check if the thickness of the base-metal exceeds the critical minimal thickness of 0.5 mm. 3) Edge effect The measurement shall not be carried out nearby abruptly changing shapes of the test-specimen. e.g. edge, hole, corner, etc. 4) Curvature The measurement shall not be carried out on curved surface of a test-specimen with a radius of curvature under 1.5 mm (convex) or 9 mm (concave) 5) Number of readings Since the readings obtained each time are not completely identical, multiple readings must be taken in each measured area. The local difference of thickness of a coating also requires to carry out the measurement many times in any given area, especially in case of a rough surface. 6) Cleanliness of surface All adhering matters such as dust, oil stain, corrosion contaminant, etc. on the surface must be cleared away before measurement without damaging the coating. 10 Manual TT-220
5. MAINTENANCE AND REPAIR 5.1 MAINTENANCE Strictly prevent the gauge from impact, dust, moisture, high magnetic field, greasy dirt, etc. 5.2 CHARGING Usually the gauge must be charged after each 8-24 hours of operation. The time of charging is 12-14 hours. 5.3 MALFUNCTION In case of the following malfunctions: 1) The gauge can t automatically switch off 2) The gauge can t measure 3) The keyboard doesn t work 4) The measured values are always changing It is necessary to reset and set a new basic calibration. This is a time-consuming procedure (see chapter 3) and asks for special technical skill. Return the gauge to your supplier or do as follows: Press the Up key and MODE Key simultaneously to reset. Now the basic calibration is lost. It is necessary to make a new basic calibration for accurate measurement, see chapter 3. If you are not in the situation to fix a basic calibration properly, then please return the gauge TT220 to your supplier for new calibration and adjustment Manual TT-220 11
5.4 TABLE OF ERROR CODES Code Meaning of code Solution E01 Defect of gauge Reset and basic calibration E02 Spare E03 Damage of probe Repair the probe E04 Measured values of probe Avoid high magnetic field or gauge aren t reliable, Carry out measurement e.g. large fluctuation of on soft coating values of measurement in with auxiliary devices magnetic field or on soft coating E05 The probe is too close to the Take probe further base-metal while switching on from base-metal. E06 The voltage of the battery Immediately charge it is too low E07 Clear malfunction. Impossible Repeat zero point calibration reset for excessively large over 15 times values of measurement E08 Gauge damaged Return the gauge to your supplier for repair 12 T20-137 Manual TT-220
T20-137