How does IR (infrared) intensity measured

[makovx]

Can a lux meter measure infrared intensity like it does for the visible light? I read from somewhere that it cannot. If you have an IR illuminator on in the dark and hold up your 'regular' lux meter to it, it will likely register 0 - an unhelpful and misleading result.

I'm just wondering if there is a filter inside the lux meter that only passes a certain amount of wavelength, and if I can change some of its circuitry in order to have a reading for IR.

I am looking for a cheap way to measure IR intensity. Or, if there is another way to measure infrared intensity (like a relationship between terminal voltage/current and temperature, temperature vs. illumination, etc.) please let me know (:

 

[Yuri B.]

Thermometer ?

 

[Mech_Engineer]

Lux and Lumens are photopic units weighted based on the response curve of the human eye. The human eye is not sensitive to infrared, therefore you cannot define a lumen for infrared wavelengths.

However, you can define infrared incident energy in radiometric terms such as power per area, e.g. W/m^2. There are instruments that can measure incident infrared energy as well, but you have to be careful in defining the wavelength band you're interested in, and the expected energy levels.

 

[Bobbywhy]

Your lux meter is meant to measure visible light. It has a light-sensitive detector which, when light strikes it, generates a photocurrent that gets amplified and sent to the (calibrated) meter readout.

Since Infrared energy is just a lower frequency your lux meter may respond to it, but the calibration would not be correct. You would need to find the "spectral response" curve of the lux meter's sensor, and if it does detect the IR band you are interested in, then you would need to re-calibrate the readout to conform to the responsitivity curve. All-in-all, it's not a very useful thing to attempt because it's complicated and may not even work.

Why not just test your lux meter? Place it in the IR beam and see if it reads anything at all. Better yet, get a new meter that is designed to measure IR intensity.

 

[alphy]

Infrared (IR) intensity is typically measured using a device called a radiometer, which is specifically designed to detect and measure infrared radiation. A radiometer works by using a sensor that absorbs infrared radiation and converts it into an electrical signal, which can then be measured and displayed as a measurement of IR intensity.

A lux meter, on the other hand, is designed to measure visible light intensity and is not capable of accurately measuring infrared intensity. This is because a lux meter uses a filter to only measure the intensity of visible light, and it is not sensitive to the longer wavelengths of infrared radiation.

In order to measure IR intensity with a lux meter, you would need to modify the device by removing the filter and possibly making other changes to its circuitry. However, this is not recommended as it could potentially damage the device and may not result in accurate measurements.

If you are looking for a cheap way to measure IR intensity, there are other options available such as using a digital thermometer with an infrared sensor or using a thermal camera. These methods may not provide precise measurements, but can give you a general idea of the IR intensity in a given area.

Another option is to use a device called a pyrometer, which measures the temperature of an object by detecting the infrared radiation it emits. This can be a more accurate way to indirectly measure IR intensity.

In summary, a lux meter cannot accurately measure IR intensity and modifying it may not be a reliable or safe option. It is best to use a device specifically designed for measuring infrared radiation, such as a radiometer or pyrometer, for accurate results.