Richmeters GY910 thickness gauge for measuring the thickness of paint and varnish coatings. Paintwork thickness gauge on arduino Do-it-yourself thickness gauge from a multimeter

Unfortunately, very often, when selling their cars, car owners resort to various tricks to hide visible flaws. So, for example, an unscrupulous car owner can put a thick layer of putty on the body of his car, which will hide scratches and small dents.
After some time, the putty will fall off, and the newly minted owner of the vehicle will “fly a pretty penny”. The Paint Thickness Gauge will help you determine if the coating thickness of a particular vehicle meets the standards. So, avoid unpleasant consequences in the future.

This device is very useful when you need to measure the thickness of the paintwork. The need for this measurement arises when the condition of the car body is examined. How to use the meter? Everything is pretty simple. The meter must be applied to a specific surface and a button is pressed. During the measurement process, you need to slightly rotate and shake the device so that the arrow deviates as much as possible. After the arrow deviates, you can read the thickness value.

Norm of thickness of a paint and varnish covering:

- ordinary paint - 0.15 ... 0.3 mm;

- metallic paint - 0.25 ... 0.35 mm.

If the thickness of the coating on the car body does not exceed the permissible norms, then you can be sure that body defects are not hidden under a layer of putty.

This device is made according to a simple scheme. Despite this, the meter gives sufficient accuracy when measuring. It is also "mobile" and compact, which is a huge plus. After all, the meter can be easily taken with you to the car market. The following figure shows the meter circuit.

When creating the device, the scheme of Yu. Pushkarev was taken as the basis. There were some flaws in his circuit, so the device did not work quite correctly. After minor changes in Pushkarev's scheme, this scheme appeared.

(if you don’t understand anything on the diagram, you can take an express course ““)

The paint coating thickness gauge is powered by a Krona battery, the current consumption is not more than 35 mA. Even if the battery voltage drops to 7V, the device will remain operational. The temperature range during operation is from ten to thirty degrees Celsius (plus). The device itself is inside a plastic box, dimensions - 120 * 40 * 30 mm.

A master oscillator is assembled on the DD1 timer (Figure 1). It generates special pulses (rectangular), the duty cycle of which is equal to two, and the frequency is 300 Hz. Rectangular pulses are converted to a sinusoid thanks to the integrating chain R3C2. This improves the accuracy of the measurement. Using the tuning resistor R5 (signal level regulator), you need to set the optimal mode for the transformer T1, which is measuring. At the output of UZCH DA1, the signal amplitude will be 0.5 V.

In the measuring transformer there are W-shaped plates, which are located end-to-end. However, there are no end plates. The metal base acts as a magnetic contactor. This base is coated with a paint coating, which is being investigated. The size of the non-magnetic gap in the magnetic circuit circuit will directly depend on the thickness of the coating. That is, the thicker the coating, the larger the gap will be. The larger the gap, the lower the voltage on the transformer (secondary winding). The larger the gap, the less the connection between the windings. The decoupling capacitors are C5 and C7. The R6C4 circuit is used as a filter that eliminates the high-frequency components of the signal.

The current in the secondary winding of the transformer, which is rectified by the VD1 diode, can be found using the RA1 microammeter. When changes occur in the GB1 battery, in the degree of its discharge, accordingly, changes occur in the amplification factor of the UZCH DA1. Thanks to the voltage regulator DA2, the gain remains stable. You can find out the battery voltage using the SB2 pushbutton switch and the R8 resistor. Measurements are taken only when the SB1 button is pressed.

In order to create a threshold that inhibits the VD1 diode, you need to use a special transistor cascade, namely VT1R9R10R11. With it, the initial offset will be supplied. Thanks to this cascade, the ammeter needle will not deviate. The only exception will be the case when there is a magnetic contact in the transformer field. Thanks to all this, it will be possible to set the maximum possible thickness on the meter, and the measurement accuracy will be as accurate as possible. There are certain limits in which thickness can be measured. Subject to all characteristics in this meter, the limits will be from 0 to 2.5 mm. The error in measurements will be 0.5 mm, if the coating thickness is from 0 to 1 mm. If the coating thickness is from 1 to 2.5 mm, then the error will be 0.25 mm. Resistor R10 can be increased to 3.9 kΩ. This is necessary in order to increase the measurement accuracy, because the measurement limits will decrease from 0 to 0.8 mm. Due to this, the scale will “stretch”, and the threshold, which unlocks the VD1 diode, will rise.

All parts are located on the printed circuit board, as shown in the figure below. One side of the board is made of foil fiberglass, its thickness is 1 mm. Initially, there was no transistor stage VT1R9R10R11 at all. Later, in the course of small changes, it appeared. The cascade is assembled as a canopy, since there is no space for it on the board.

The device has both fixed resistors and trimmers. Permanent - MLT-0.125, and trimming - SPZ-276. Capacitors C4, C2 and C1 include KM-6 (or K10-23, K10-17). Capacitors C6, C5 and C3 include K50-35. As an ammeter, a recording level indicator is used (the part was taken from an Elektronika-321 tape recorder). Microammeter indicators:

- deviation current (total deviation) - 160 μA;

- resistance (frames) - 530 Ohm.

In order to wind the transformer T1 on the magnetic circuit Ш5Х6, you need to use a transformer from a pocket receiver. You can take both the output and matching transformer. There will be two hundred turns in the primary winding, and four hundred and fifty turns in the secondary. The wire used for windings is PEL 0.15. You will also need plates (W-shaped). The plates are smeared with epoxy glue, then (after the glue has dried) the ends of the package are processed with a velvet file. The transformer is glued inside the device, in a rectangular hole in the box. In this case, the ends of the magnetic circuit (working ones) should protrude by 1 ... 3 mm. outside of the box.

Parts usage and replacement:

1. Timer KR1006VI1 - you can use LM555 instead.
2. Stabilizer KR1157EN502A - you can take KR142EN5A (L7805V) or 78L05 as a replacement. The 78S05 is best as it gives the least power output. A lot of power is not needed.
3. Differential amplifier DA1 - KIA LM386-1 (microcircuit) is used as this part.

The motor of the resistor R7 should be in the middle position, only after that you can start setting up the device. The transformer (with the end of the magnetic circuit) must be attached to the steel sheet (clean and flat surface). Further, using the resistor R5, the arrow must be set to the final division in the scale of the ammeter PA1. The instrument must be calibrated. This is done by laying paper sheets between the metal surface and the transformer. The thickness of the sheets should be 0.1 mm (density - 80 g / m2). Paper can be used the most common, A4. Before starting the calibration, the body of the device must be disassembled, and a graph paper should be placed under its arrow. The graph paper will record readings during the calibration process. Then, using a graphic editor, you need to draw a scale, print it on a printer (color) and carefully paste it inside the device. After that, the device can be assembled.

Resistor R8 must be selected correctly. When using a new battery and pressing the SB1 and SB2 buttons, the following should happen - the arrow on the microammeter should deviate to the final division on its scale. Be sure to note the division on the scale when the battery is discharged. It can be determined by taking measurements with the battery connected, discharged to 7V. You can also use an AA battery to determine the division when the battery is discharged. The battery must be connected in series with the Krone, while not forgetting to change its polarity. Next, you will need to calculate the difference between the values ​​\u200b\u200bwith and without a battery, and then add one quarter to this difference. This will be the desired value on the scale when the battery is discharged. The scale can be divided into two colors: the normal state is in green, the discharged state is in red.

On a note:

- if the device is used in bad weather conditions and low temperatures, then you need to keep it warm, in your pocket, and take it out just before the measurement itself.

- if the magnetic circuit used has a Ш8Х8 core, it will be necessary to reduce the frequency of the generator. This can be achieved by increasing the value of C1 to a value of 47 nF. Then the performance of the device will be at the highest level.

– Only pure metal materials may be used in the calibration process! If materials that contain various impurities are used, the device may not react to them.

12 volt antifreeze heater 12 Volt DC Motor Speed ​​Controller

This car paint gauge chart can determine with a high degree of accuracy whether the car being tested has undergone a body repair procedure, which is especially true before buying a used friend on wheels.

The generator assembled on the domestic timer KR1006VI1 generates rectangular pulses with a repetition rate of about 300 Hz and a duty cycle of two. At the output of the generator, in order to improve the accuracy of the results of measuring the thickness of the paintwork, there is a low-frequency filter on resistors and capacitors R3, C2, R4, R5. Trimmer resistance R5 is a level regulator that sets the optimal level of operation of the device. A low frequency amplifier is assembled on the LM385 chip.

The transformer is actually the measuring sensor. It is made of W-shaped plates without closing plates, because their role is performed by the car body. Thus, the higher the thickness of the paint coating, the higher the non-magnetic gap and therefore the smaller the coupling between the transformer coils. To cut off high-frequency interference at the output of the amplifier, there is a filter R6C4. Capacitor C5 is separating.

The results of measurements of the thickness gauge of the car paintwork are obtained using a tester with a KD522A diode. The 78L05 stabilizer allows the circuits to work with the built-in measurement accuracy and when the power supply of the krone battery is reduced to 7V.

Switch SB1 allows you to check the degree of rarefaction of the battery. The measurement is carried out with the button SB2 pressed.

The transformer was borrowed from a radio receiver with a W 5x6 magnetic circuit and slightly rewound. The primary winding contains 200 turns of PEL 0.15 wire. Secondary - 450 turns of the same wire. When assembling the transformer plates, they must be coated with epoxy glue.

The adjustment of the automobile thickness gauge is carried out by setting the R7 potentiometer engine to the leftmost position. The transformer must be placed away from any metal objects. By rotating the resistance slider R5, you need to achieve a deflection of the microammeter needle by five percent. Then the transformer is leaned against a clean steel sheet and by changing the value of the resistance R7, the maximum possible deviation of the microammeter needle is achieved. Then the device is simply calibrated by placing sheets of paper 0.1 mm thick between the steel sheet and the transformer.

To obtain the results of measuring the thickness of the car paintwork, you need to attach the transformer to the surface under study, then press the SB2 button and slightly shake the device from side to side to achieve the maximum possible deviation of the ammeter needle. The thickness of the factory paintwork in a car is usually about 0.15 ... 0.3 mm, and metallic paint 0.25 ... 0.30 mm.

I propose to assemble a thickness gauge circuit on an inductive sensor. The sensor, as in the previous case, will be a miniature W - shaped transformer, assembled on one side of the coil, without end plates. If its open side is leaned against a metal surface, then, depending on the thickness of the non-magnetic gap, the inductance of the coil changes. One way to measure the thickness is to connect the coil as the inductance of an LC oscillator. Then the signal goes to the detector, and then to the display device.

In the process of searching for a used car suitable for me, I was faced with the need to check the paintwork (LCP) for uniformity, to identify painted or putty parts. At first, a professional paintwork thickness gauge fell into my hands, but they didn’t give it to me for long, and the process of finding a car, on the contrary, was stretched out in time. The meter had to be returned to the owner, and a suitable machine was not found.
Is it possible to make the simplest paint thickness gauge yourself?
The first result of an Internet search was a classic circuit based on a two-winding transformer with an open magnetic system.

A signal is applied to the primary winding, and a signal is sent to the meter from the secondary winding. The measured sample closes the magnetic system and the thicker the paint, the less the connection between the windings, the lower the output signal. But it was too lazy to look for suitable iron for the transformer and wind it, continued the search. In addition, such schemes have a strong nonlinearity in the dependence of the signal level on the coating thickness.
Then I came across a circuit that works based on a change in the inductive resistance of the sensor. A calibrated signal (preferably sinusoidal) is applied to the measuring coil, the coil is included in the arm of the measuring bridge, after zero is set, the measurement is taken.

Couldn't it be even simpler? The train of thought is something like this: "if the sensor is an inductance, then you need a device for measuring inductance"

I also remembered that I have several Arduino boards lying around. Took a couple of years ago to play.
I formulated, for myself, the task - "Measuring the inductance on the Arduino with a minimum of attachments."
As a result of searching, I came across the page https://github.com/sae/Arduino-LCQmeter/blob/master/LC-gen.ino
this program became the prototype of the simplest LKP meter.
As the main board, Arduino nano was chosen for its small dimensions.
The essence of the work is as follows: a “pump” pulse is applied to the measured LC circuit, after which the counter is started until the signal on the circuit passes through the “0” of the comparator, after which the process is repeated.
As a result, the counter reading is proportional to the resonant frequency of the LC circuit.
At first I tested the idea on the table, with the output of information to the computer. It seems to work
Although I had an LCD module, but with it the device turned out to be bulky and required the manufacture of a case.
I decided to make an indication of the thickness on the LEDs.
I drew a diagram, soldered the shield on a breadboard, provided for battery voltage control.

The problem turned out to be the manufacture of the coil. If I found many and different cups of ferrite armor cores, then I did not find a single coil frame. After several attempts to make the frame myself, the following solution was found: two cardboard cheeks were installed on the conical body of a ballpoint pen, and approximately the appropriate number of turns were wound to fit inside the core. The wire took the minimum thickness that was at hand (about 0.08), I don’t remember the number of turns, something around 100. After winding, I removed one cheek. and pushing the other cheek, he placed the resulting coil inside the core. Dropped coils, tucked into the coil with tweezers. After that, he dripped superglue onto the coils and closed the coil with the remaining cheek. I fixed the coil on the board with hot glue.
The capacitor is preferably metal-film, but not ceramic, since ceramics of such a capacity have an unacceptable TKE
As a result, we got this design:

Program text for download:

Working with the device:
Since different machines have different paint thicknesses, the calibration procedure is done first. In addition, the calibration procedure makes it possible to reduce the influence of temperature on the measurement results. To calibrate, you need to press the device to the surface of the car, and press the "calibration" button
After the calibration, the value of the thickness of the paintwork, expressed in "arbitrary units" is written to the eeprom.
to carry out the measurement, the device is applied to different places of the car's paintwork and the "Measurement" button is pressed. If the deviation of the measured result from the recorded one is small, the green LED lights up.
If the deviation exceeds a certain limit - the white LED lights up - "suspicious"
If there is a second layer of paint, or there was polishing, one of the blue "paint" or "polishing" lights up
If the coating is close to zero or exceeds 0.2, then the red LEDs "putty" or "metal" light up
Each thickness measurement is taken 3 times and then the value is averaged. Perhaps once is enough. This will allow you to get results almost instantly.

Do not consider this craft as a sample of the finished product. This is just an example of how you can solve the problem with "improvised" means. But, I suspect that on the basis of this meter, you can make a meter with professional accuracy. To do this, you will need to wind the coil with high quality, select a capacitor with a minimum TKE, connect the screen module, select the formula for converting the "raw" value into micrometers.

Boris Padorin, LLC "Dolina-Service"

In works related to the application of a protective coating on steel surfaces, it often becomes necessary to determine the thickness of the layer or the thickness of the paintwork and other materials when buying a used car. Despite the apparent complexity, this can be determined in several simple ways.

In industrial devices, ultrasonic thickness gauges are usually used for this, which work on the principle of echo - location. A sensor is applied to the protective layer, which is a piezoelectric transducer, to which packs of ultrasonic vibrations are fed. The ultrasonic signal passes through the protective coating and is reflected from the metal surface. The reflected signal is captured by the sensor, amplified and fed to a phase detector, which compares the phase of the transmitted and reflected signal, and then produces a signal proportional to the delay time, and hence the thickness of the coating. This method is quite accurate, but very difficult to implement independently. Simpler devices can be made on the basis of capacitive or inductive sensors. The measurement errors of these devices are much higher than those of ultrasonic meters, but in most cases this is not important. If the coating is paintwork, then you can use a capacitive sensor, which is two small metal plates glued to a dielectric base and pressed against the surface of the layer. Between the plates, the capacitance is measured, which depends on the dielectric constant of the coating and on its thickness. The device must be calibrated for each type of paintwork. More convenient inductive sensors. The sensor is a miniature W - shaped transformer, assembled on one side of the coil, without end plates. If you press it with the open side against a metal surface, then depending on the thickness of the non-magnetic gap formed by the protective coating, the inductance of the coil changes. One way to measure is to include the coil as the inductance of an LC - low frequency oscillator. Next, the signal is fed to the frequency detector, and then to the display device. The method is good, but rather complicated. A diagram of a simpler device, but fairly accurate, is shown above.

The device is a generator of stable frequency and amplitude, in series with the output, which turns on an inductive sensor, the resistance of which is proportional to the square root of the inductance. The voltage after the sensor is detected, normalized and fed to the display device. For indication, you can use a small dial indicator, re-calibrating its scale, but LED indication is more convenient. In the proposed device, a transformer from a subscriber loudspeaker (radio point) is used as a sensor. The transformer is assembled on one side, without end plates, and filled with epoxy together with the rest of the elements, in a small case. The working surface of the sensor is polished to a metal shine. The advantages of the device are its small dimensions and the ability to measure the thickness of any non-magnetic coatings, even electrically conductive ones, for example, the thickness of aluminum deposition or copper plating on a steel surface. The instrument is calibrated using non-magnetic plates of known thickness. The circuit can use any low-voltage operational amplifiers with low current consumption. For the selected types of op amps, the resistances of the resistors between terminals 4 and 8 set the consumed current and amount to 1 ... 1.5 MΩ. You can use dual op amps, such as LM358 or similar. The K561LA7 chip can be replaced with K561LE5 or any inverter logic elements. If you want to improve the accuracy of the analog-to-digital converter, you can use the LM339 quad comparator instead of a digital microcircuit. You can simplify the circuit even more by using the A 277 (K1003PP1) chip for linear light indication, although the current consumption will increase. In this case, the K561LA7 and KR1533ID3 microcircuits, together with the strapping resistors, will not be needed - the input of the microcircuit is connected to the output of the second op-amp. The NE555N timer (KR1006VI1) in the circuit is used not only as a stable frequency generator for the sensor, but also as a negative polarity inverter to obtain a voltage of -2 V, which is necessary for the normal operation of the op-amp. A properly assembled circuit starts working immediately - it remains only to individually calibrate the LED bar for indicating trimmers and non-magnetic plates of known thickness.

When assessing the technical condition of a used car, the first thing they pay attention to is the body, whether there are any defects on it. In addition to the obvious damage visible to the naked eye, there are others hidden from the inattentive gaze. To say for sure whether a used car has hidden defects, you need to know the exact thickness of the paintwork: if you had to deal with used car dealers, then you might notice that they carry a special device with them, with which, within two to three minutes can determine whether the car was involved in an accident or not.

In some cases, a thickness gauge can save you a lot of money.

This device is the paintwork thickness gauge. In skillful hands, such a device helps to find out a lot of useful information about the past of a used car.

Types of thickness gauges

Today, there are several types of this device on the market with a variety of operating principles, but the most common among motorists are ultrasonic, magnetic, electromagnetic and eddy current thickness gauges. Their price and capabilities, of course, differ from each other, so we will consider each type and its specialization separately.

Ultrasonic Thickness Gauge

• Ultrasonic thickness gauges. They are a universal solution for checking paintwork with a thickness gauge: this paint thickness gauge works equally well not only on metal surfaces, but also on composite materials, ceramics and plastics, which gives ample opportunities for use: you can qualitatively check the paintwork with an ultrasonic thickness gauge not only on the body , but also on the decorative component of the car, such as a plastic bumper or a carbon insert.
  The only downside is the price. The cost of the simplest ultrasonic thickness gauge for car paintwork starts at 10,000 rubles. However, such a device is considered professional, not focused on the average buyer, so this drawback, one might say, is far-fetched.

The simplest and most inaccurate magnetic thickness gauge

• Magnetic thickness gauges. They work according to the following principle: the device contains a magnet connected to an arrow pointer. You just have to attach the thickness gauge to the car body: the thinner the paint layer on the car, the stronger the attraction of the magnet to the body, the arrow will deviate more. Accordingly, the smaller the angle of inclination of the arrow, the thicker the level of coating on the body, which should alert you. The advantages of thickness gauges with a magnet include ease of operation, no need for batteries and a low price - the cheapest such unit costs about 450 rubles. However, such thickness gauges also have disadvantages. The most serious: low accuracy of readings. These devices show more or less correct results if the coating layer does not exceed 1.5 millimeters.

• Electromagnetic thickness gauges LKP. They are considered the most reliable and practical devices, since they give the most accurate results, and the cost does not exceed 3,000 rubles. Alas, there are also disadvantages. Checking the paintwork with an electromagnetic thickness gauge makes sense only on surfaces with an impurity of iron. Such an aggregate, as they say, will not pull plastics and non-ferrous metals - remember this at the time of purchase.

Eddy current thickness gauge Et 11S

• Eddy current thickness gauges. Its “trick” is the ability to estimate the thickness of the applied coating on any metals, besides, it gives the most accurate measurement results. The disadvantages of such devices include the dependence of measurements on the electrical conductivity of the metal whose coating thickness you are measuring. That is, when working with copper, aluminum and other metals with good current conductivity, the measurement results will always be accurate. But using a paint thickness gauge on, for example, iron, errors will appear in the measurements, sometimes very serious ones. An eddy current automobile thickness gauge costs around 5,500 rubles.

How to properly use and calibrate the instrument

It is necessary to use the thickness gauge wisely, otherwise it simply does not make sense. Here are a few simple tips for those who want to use a thickness gauge productively to check the thickness of a car's paint.

Buy smart. The cheaper the thickness gauge, the less its functionality: the cheapest measurement solution will help you understand whether the car was puttied or not, but there will be problems with determining an additional layer of paint. In addition, not all surfaces can be measured. To work with aluminum, you need to purchase a more expensive device, and for plastic, you will have to fork out for an ultrasonic thickness gauge, the price of which can be no less than a cheap used car.

In order not to waste money, buy a car thickness gauge with a knowledgeable person, or contact a sales assistant: explain the situation to him, and he will tell you which unit is right for you.

If your friends have a thickness gauge that suits you, just ask for it for a while. By the way, some car companies have a service for renting a paint thickness gauge. Instead of buying, you can rent a device for a small price while buying a used car.

Calibration

Video: Setting up and calibrating the thickness gauge model CHY 115

The first thing to do after purchase is to calibrate. Of course, in production, thickness gauges are calibrated, but a new unit needs to be checked. Calibrate when temperature fluctuates or when batteries are changed.

In order to calibrate the paint thickness gauge, reference plates made of plastic or steel are used, on which a layer of paint of a certain thickness is applied. If, for example, the device works with steel and aluminum, then the kit will include steel and aluminum plates for calibration. Also included is a calibration film on which measurements are made.

Calibration process:

Calibration plates with film

1. Place the thickness gauge on the desired plate and reset the values ​​displayed by the gauge.
2. Next, put the device on the calibration film and wait until the device gives out data
3. Numbers are printed on the calibration film. The same indication should be on the dial of the thickness gauge.

If the readings are different, readjust your machine so that the readings on the film and on the instrument match. If you neglect calibration, it may backfire on you in the future.

Adjust the thickness gauge for each specific case separately. Today, most thickness gauges have a range change function - always use this function, as it greatly reduces the possibility of incorrect measurement.

How to check a car with a thickness gauge

Use the thickness gauge correctly. This is important because the result of your measurements depends on it. For measurements, use the following algorithm:

Body paint thickness chart for various car brands

Before working with a thickness gauge and measuring the thickness of the paint, it is necessary to clean the car. On a dirty body, the readings of the device will be inaccurate.

Using a thickness gauge, apply it to each part of the body, starting with the front wing (any), then moving along the entire body. Measurements on each part of the body (hood, roof, door, fender, etc.) are carried out at 3-5 points, preferably at the edges and in the center. The device is applied perpendicular to the body part, if at an angle, then the readings of the device will be inaccurate.

Be sure to check the paintwork inside the body - in the cabin. Open the door and measure the thickness of the paint on the racks, measure the paintwork of the frame, where there will be access.

After taking all the measurements, calculate the arithmetic mean for each part, compare the obtained values ​​\u200b\u200bwith each other. Take several measurements in a row to get the most accurate result. There is always an error, so never trust the numbers obtained after one measurement - it is better to take several measurements and calculate the arithmetic mean, this guarantees the maximum reliability of the data.

Video 1: How to measure paint thickness with a thickness gauge

Pay attention to thick sections of bodywork. When measuring, keep in mind that the places of the body with a new painting differ in thickness from the places where there is a layer with only factory paint. Most often, the repainted places are 2-3 times thicker. If, when taking measurements, you find a section that is 100-150 microns thicker than the rest of the body, then you can be sure that it was repainted. If the thickness exceeds 160 microns, then there is a possibility that this place on the car body was also puttied.

There are also reverse situations: for example, the average thickness of the paintwork is 110 microns, and in some place it is less, about 80-90 microns. Why? Apparently in this place the body was polished using polish, which contains abrasive materials - during such polishing, a small layer of coating is removed.

Video 2: How to measure paint thickness with a thickness gauge

When measuring, pay due attention to the sealant and the gaps between the body elements. A layer of sealant is applied at the welding points of the body components, on the doors, the rear panel of the car, inside the hood. If you find that there is no sealant, or it is applied unevenly, and the bolts are not covered with paint, or there are chips, then this means that the part was removed for repair or replaced with a new one. Some used car dealers don't wash the car on purpose so you don't have to check the condition of the sealant. So if the seller doesn't want to take the car to the car wash, he may be afraid that you will find a lot of chips.

Look at the gaps of the car doors, trunk, hood when they are closed: if they are different, or the opening elements cling to the body, then they may have been replaced, or an additional layer of paint has been applied.

Use a paint thickness gauge to determine where "crossovers" are located on the vehicle. These are places where coating layers merge from various car body parts; these places cannot be found without special devices. Transitions are found in those places of the body where it is impossible to unscrew the parts.

An amateur is not a professional. Of course, finding out the past of the car by the thickness of the coating is the easiest way, but it will not always help. Auto repair shops also employ not the most stupid people who are well aware of the thickness of the factory body paint and will adjust the new coating layer to the range used by the manufacturer of a particular car model.

In addition, in some cases, a different thickness of the coating on the body is normal. Parts of the car are painted individually, or using different painting technologies, which, of course, affects the thickness of the paintwork. The error of factory painting ranges from 10 microns to 35 microns, while it is necessary to take into account the possible error in measurements of an automobile thickness gauge (2-4 percent).

As you can see, there are a lot of subtleties, so do not hesitate to turn to an experienced person who can literally determine by eye whether they are deceiving you or not.

What should measurements show?

As a rule, on modern cars, the thickness of the paintwork does not exceed 200 microns.

1. Therefore, if a measurement with a thickness gauge shows 200 - 300 microns of paint, then this indicates a slight re-painting, for example, a scratch has been painted over. This does not affect the technical characteristics of the car in any way, but it gives a reason to bargain.
2. If the values ​​​​are from 300 to 1000 microns, then there is putty under the paint, and this is a risk that over time it will crack and fall off along with the paint.
3. If the numbers on the thickness gauge show more than 1000 microns, then the car was in a major accident and it is better to refrain from buying.
4. The maximum that the device can show is 2000 microns, which indicates that the putty layer is very thick.

Video: How to choose and what is inside the thickness gauge.

Is the thickness gauge worth the money?

Yes, it’s worth it: the thickness gauge of the paintwork can fully pay off during the first purchase of a car: for example, if you find body defects, you can drop $ 150-300 from the price of the car, depending on the situation and the pliability of the seller.

All information in the article is purely promotional in nature, since technology does not stand still, cars are painted using the latest developments, so first of all, consult with specialists.