Incomplete disassembly of blackbody radiation source

littleshrimp

Incomplete disassembly of blackbody radiation source [Copy link]

This is a common but not commonly used thing. It is common because in many occasions where thermal imaging temperature measurement is required, a black body radiation source may be placed opposite the thermal imaging. Because thermal imaging is easily affected by ambient temperature, in order to compensate for the thermal imaging temperature measurement error, placing a black body radiation source in the "crowd" can achieve temperature compensation for thermal imaging.

An ideal black body does not reflect any light and has an emissivity of 1. At this time, we can only measure the radiation of the black body itself. The indicators of a device such as a black body radiation source include the emissivity, uniformity, and temperature control accuracy of the black body. Theoretically, the closer the emissivity is to 1, the better, so that it will not be affected by external radiation. Uniformity refers to the temperature difference at various locations on the target surface, and the smaller this temperature difference is, the better. Finally, its control accuracy. In addition to temperature compensation for thermal imaging in public places, a black body radiation source can also calibrate thermal imaging or infrared temperature measurement sensors in the laboratory. If you want the calibrated sensor to have high accuracy, you need a higher-precision calibration source.

From the outside, this blackbody radiation source is just an aluminum shell with a black target surface on the front and a temperature controller on the back.

After removing the screwed back cover, there is a Yudian thermostat on the back. The instruction manual states that the accuracy of this black body is 0.3 degrees Celsius, so the control accuracy of this thermostat is basically the same.

This thing may seem mysterious, but in fact, you can guess its structure and principle without taking it apart. It is similar to a constant temperature control box or a constant temperature heating plate. The difference is that it only heats a target surface with low reflectivity (high emissivity).

Remove the back cover and the top cover. On the right is an external thermostat and a 24V powered fan. On the top is a solid-state relay control board. Because the control current of the thermostat is limited, an external solid-state relay control board is required. At the bottom is a 220 to 24V switching power supply. On the left are components such as the heating plate.

The lower left corner is the heating plate, and there is an aluminum plate on the back of the heating plate, which is fixed with 4 screws. There are 3 sets of lines on the target surface, one set of temperature measuring lines connected to the thermostat and one set of heating lines connected to the solid-state relay, and another set is also connected to the control board of the solid-state relay. I don't know what it is used for.

The side of the thermostat.

Wiring on the back of the thermostat

Unscrew the 4 screws of the heater to remove the front and back metal covers.

From the side, the heating plate consists of an aluminum core, an outer shell and foam on the back. Unfortunately, the foam is difficult to remove. Because this device is newly purchased and has not been used yet, I don’t want to damage it and affect future measurements, so I won’t disassemble it further.

Finally, attached is a picture of using a multimeter to measure the 24V voltage output by the switching power supply during operation, which ends this incomplete disassembly.

tagetage

I have learned it. But I don't understand why it heats a target surface with low reflectivity (high emissivity)?

dcexpert

Looks very practical

littleshrimp

tagetage published on 2021-12-13 13:15 I have learned it. But I don’t understand why it heats a target surface with low reflectivity (high emissivity)? ?

Heating the target surface can keep it at a constant temperature

bigbat

What is the temperature range of this black body? It only gives an accuracy, which is a bit vague. I don't know what it is used for.

littleshrimp

bigbat posted on 2021-12-13 16:11 What is the temperature range of this black body? It only says an accuracy, which is a bit vague. I don't know what it is used for.

Room temperature +5 degrees Celsius ~ 50 degrees Celsius, mainly used in applications where thermal imaging is used for temperature measurement, such as railway stations and airports where dynamic monitoring of pedestrian body temperature is required.

迈尔风随

I roughly understand the principle, but I still don't quite understand how to use the original scene. Use it to illuminate the object being tested and compensate for the heat?

littleshrimp

Mayer Fengsui published on 2021-12-13 20:00 I roughly understand the principle, but I still don’t quite understand how to use the original scene. How to use it to illuminate the object being tested and compensate for the heat?

It is a reference source. The field of view of thermal imaging includes both black body radiation sources and pedestrians. If the temperature of the black body is set to 36.5 degrees Celsius, then by comparing the measured black body temperature with the temperature data of the pedestrian, we can know whether there is a fever. I said compensation may not be appropriate, and it may be easier to understand to say calibration.

se7ens

Thanks for sharing, it made me understand the function of this thing

迈尔风随

littleshrimp posted on 2021-12-13 13:13 It is a reference source. The field of view of thermal imaging includes both black body radiation sources and pedestrians. If the temperature of the black body is set to 36.5 degrees Celsius, then the comparison measurement...

That is used as a reference temperature point, for other test things as a reference, so you understand it.

littleshrimp

Mayer Fengsui published on 2021-12-15 20:24 It is used as a reference temperature point, for reference of other test items, so you can understand it

That's right