▲▲Infrared thermometer: when measuring the water temperature in a cup vertically, does it measure the surface of the water, the bottom of the cup, or something else? ? ?
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As shown in the figure, I want to quickly know the water temperature in the cup (no need for high precision). I used a temperature meter (VICTOR303B) to send infrared rays into the water from top to bottom. (Infrared light is projected onto the bottom of the cup, or even onto the table surface.) Do the data I obtain represent the temperature of the water surface in the cup, or the temperature of the bottom of the cup, or the temperature of the table surface? ? ? In short, can this thermometer be used to roughly measure the water temperature in a cup? If it’s clearly unscientific, what is the main problem?
My understanding is that it refers to the temperature of the water’s surface; if I have already stirred it, this value can be used to indicate the temperature of the water in that cup. I plan to explain it in class like this; I’m not sure if that’s okay
Is it necessary to measure temperature perpendicular to the surface? No. Viewing from a low angle frequently can help avoid obstacles in light paths or high-temperature environments. When viewing rough surfaces such as high-temperature steel strips, the aiming angle of the sensor can be set at 15° above the horizontal plane. When viewing glass, plastic, or paper, the minimum allowable angle is 45°.
The temperature of the water surface can only be measured at the surface level
I think there might be a misunderstanding regarding the principle of infrared thermometers. These devices measure the infrared radiation emitted by an object due to its temperature; it’s not visible light. The beam emitted by the thermometer is used solely for distance measurement, and it is based on this data that the intensity of the received infrared radiation is calculated to determine the temperature. So what can be measured is only the surface temperature of the object under test; however, distance measurement seems to be inaccurate in this scenario. Whether this will result in an overestimated temperature depends on the manufacturer’s instructions.