Do you know the basic methods of infrared detection? What is eddy current detection?

The importance of detection technology is self-evident. To a certain extent, detection provides a guarantee for our safety. In previous articles related to detection, the editor explained about oxygen detection and photoresistor detection technology. In order to improve everyone’s understanding of detection technology, this article will introduce infrared detection and eddy current detection.

The importance of detection technology is self-evident. To a certain extent, detection provides a guarantee for our safety. In previous articles related to detection, the editor explained about oxygen detection and photoresistor detection technology. In order to improve everyone’s understanding of detection technology, this article will introduce infrared detection and eddy current detection.

Do you know the basic methods of infrared detection? What is eddy current detection?

1. The basic method of infrared detection

The basic methods of infrared detection are divided into two types, namely passive and active.Passive infrared detection is widely used in the infrared detection and diagnosis technology of equipment; active infrared detection can be divided into single-sided method and double-sided method

In infrared detection, the heating method of the measured target is also divided into steady-state heating and non-steady-state heating.

There are many ways to install and carry infrared detection instruments, such as fixed, portable, vehicle-mounted and airborne (helicopter loading).

(1) Passive infrared detection

The so-called passive type refers to the method of infrared detection during the heat exchange process between the target and the environment without heating the target under test and only using the condition that the temperature of the target under test is different from the ambient temperature. Passive infrared detection is used in running equipment, components and scientific experiments. Since it does not require an additional heat source, this method is basically adopted at the production site.

(2) Active infrared detection

Active infrared detection is to actively heat the measured target before infrared detection. The heating source can come from the outside or inside of the measured target. There are two heating methods: steady state and non-steady state. Infrared detection can be based on different conditions. It is carried out during the heating process, or it can be carried out after the heating has been stopped for a certain period of time.

1) Single-sided method: The heating and infrared detection of the measured target are performed on the same side of the measured target.

2) Double-sided method: Compared with the above-mentioned single-sided method, the double-sided method separates the heating and infrared detection of the measured target.

Perform on the front and back sides of the target.

(3) Heating method

1) Steady-state heating: When the measured target is heated until its internal temperature reaches a uniform and stable state, then it is placed in an environment lower (or higher) than the constant temperature for infrared detection.

This method is mostly used for quality inspection of materials. If there are defects such as cracks, holes or debonding inside the tested object, the heat flow in the heat exchange between the tested object and the environment will be hindered by the defect, and the corresponding outer surface will be blocked. There will be a temperature change, and there will be a temperature difference compared to a surface without defects.

2) Unsteady heating: heating the target to be measured does not need to make its internal temperature reach a uniform and stable state, and infrared detection is performed when its internal temperature is not uniform and has heat conduction.

3) If the heat is evenly injected into the measured target, the speed at which the heat flow enters the interior is determined by its internal condition. If there is a defect in the interior, it will become a thermal resistance to block the heat flow. After a certain period of time, heat accumulation will occur. The corresponding surface will produce thermal anomalies. The change in heat flow caused by defects depends on the location, orientation, geometric dimensions and thermophysical properties of the material.

2. Eddy current testing

Eddy current is when a conductor is placed in a changing magnetic field, due to the vortex induced electric field around the changing magnetic field, the induced electric field acts on the free charge in the conductor to move the charge and form an eddy current.

Do you know the basic methods of infrared detection? What is eddy current detection?

Eddy current Testing (abbreviation ET). Known Faraday’s law of electromagnetic induction, an alternating current is connected to the detection coil to generate an alternating magnetic field perpendicular to the workpiece. When the detection coil is close to the workpiece to be inspected, the surface of the workpiece induces eddy currents and simultaneously generates a magnetic field opposite to the original magnetic field, which partially offsets the original magnetic field, resulting in changes in the resistance and inductance of the detection coil. If there is a defect in the metal workpiece, the intensity and distribution of the eddy current field will be changed, and the impedance of the coil will change. By detecting the change, it can be judged whether there is a defect.

Do you know the basic methods of infrared detection? What is eddy current detection?

With the development of microelectronics and computer technology and the adoption of various signal processing technologies, eddy current testing transducers, eddy current testing signal processing technologies, and eddy current testing instruments have developed rapidly.

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