Surface Temperature versus Air Temperature

Surface temperature, in essence, is the temperature as measured at the "skin" of a specific object. It isn't necessarily the temperature of the object itself, but rather the temperature just at the outside of the object, being that surface temperature is affected by A) the temperature of the surrounding air (ambient air) and B) the temperature of the core that the object and C) the surface temperatures of any other objects that may be touching the object (i.e. a temperature probe). Each of these systems push and pull the temperature of the object's surface until a thermodynamic equilibrium is reached between all the relevant thermal systems. The time in which equilibrium is met depends greatly on the temperatures differentials between the systems, the materials involved as well as the density of the object that is being measured. Granted, the surface temperature is a relatively accurate measurement for the overall temperature of the object, but this wouldn't be true if the o!
bject was in the state of being heated or cooled from within. Barring that, and for most cases that a paranormal investigator would run across, this wouldn't much matter. However, to understand this dynamic can assist when temperature readings are unusual and a rational reason for the unique data point is being sought.

The Pitfall

Through my own experiences on investigations and my reading of many investigation reports, it is my opinion that many investigators are mistaking the readings provided by their IR thermometers. When an area feels cold, a quick reading is taken and offered up as a validation for what they are experiencing. I have also seen good investigators discounting their own logic by refusing to question what their equipment is telling them. If the meter reads 35 degrees, it must be 35 degrees regardless of what their senses are telling them. Either way, this type of data collection is wasteful and misleading, resulting in a false positive that can waste hours of valuable investigation time and provide for some red faces when the data is scrutinized.

What does an IR thermometer measure?
An IR thermometer was designed specifically to measure the surface temperature of an object. If the intension is to measure the temperature of a particular object rather than the ambient air temperature, then this is definitely the tool that would need to be used. I certainly wouldn't hesitate to use this tool on an object that someone claims to have an energy attached to it. The beauty of the tool is that you aren't touching it; therefore you are not risking the transfer of heat between the object and a temperature probe nor your hands, which could be a significant factor when dealing with phenomenon that lasts seconds in duration. This tool is perfect for this application as this is the intended design of this type of thermometer.

In my research of this device, I have heard the incorrect claim that these devices, much like a camera, have a focal point and if you simply stand far enough away from any object, you are measuring the heat at that point in space. In a round about way, the claimants are stating that an IR thermometer is essentially measuring the temperature of the air out in front of the sensor. This is simply not true and, in fact, this action may give bizarre readings making the investigator wonder if something is there or not.

Heat is transferred in three distinct ways - conduction, convection, and radiation. Conduction involves the transfer of heat through solids. Convection involves the transfer of heat through liquids or gases. Radiation involves the transfer of heat through empty space, or a vacuum. These are all simple statements, but what really should understood is that IR thermometers deal with only one of these measurable properties - radiation. Electromagnetic energy, such as light or radio waves, are familiar examples of radiation. Heat is also transferred via radiation just as the sun warms the Earth through radiated energy traveling through 93 million miles of empty space. The amount of heat that is being radiated is directly proportional to the intensity (amount of light energy) the object emits. IR thermometers simply measure the intensity of the infrared radiation at a specific infrared wavelength, as defined by the specific IR thermometer's specifications.

To directly address the belief that an IR thermometer can be used to measure air temperature, it should be understood that the absorption coefficient (how much heat an object can store) of air is very small in the infrared wavelength ranges. This means that you will pickup a very small amount of the infrared from the surrounding air, but the radiance from the objects in front of the sensor are more likely to sum into your reading. Therefore, you are effectively measuring the small amount of radiance from the air between the sensor and any stray radiance from other objects that the sensor happens to be pointing at, regardless of how far away it is. The properties of infrared light is the same as visible light, particularly that it will travel through clear air without much loss in intensity.

This isn't to say that the distance between the sensor and the object isn't important; however, the importance isn't in "what" you are measuring, but how accurate the measurement is. Most IR thermometer manufactures recommend a 1.5 to 2 target size to distance ratio. What this means is that you multiply the size of the object by 1.5 to 2 to come up with the distance that the sensors should be away from the object in order to give the most accurate measurement.

What is the alternative?

My recommendation is to use a thermocouple based temperature measurement device. Most thermocouple devices have a measuring unit of less than 3cm which would be more capable of accurately and decisively measuring rapid changes of ambient air temperature. It is feasible that a moving cold spot could be followed and/or mapped with such a tool that could react quickly to changes in air temperature. It is my opinion that these types of thermometers are far better suited for the purposes of the average paranormal investigator.

In making the selection for my recommendation, I was looking for something accurate, easy to use and comparable in price to the average recommended IR thermometer. I have chosen the Omega HH501AT digital thermometer as my recommendation for this application. This device comes with a "T" type thermocouple, which has faster response times in the temperature ranges that a paranormal investigator is concerned with. Overall, this was the best all around meter that I could find that works right out of the box.

What should I do with my IR Thermometer then?

What can affect the IR thermometer measurements?

The emission from an object may be influenced by absorption and scattering in the optical path. Given that the only thing the IR Thermometer measures is emission of radiated energy, this means a lot. Water vapor, smoke, dust and various gases, such as CO2, can drastically affect these measurements. Think about it this way, if the object is being obstructed by a slightly opaque material, the radiated energy is obviously lessened. Remember that infrared light is subject to the same physics as visible light.
If there is excessive dust, dirt, fingerprints, etc collecting on the sensor's glass plate an accurate temperature measurement would be next tom impossible. As with any piece of equipment, your IR Thermometer will need to have some basic general maintenance.
Polished metal and mirrored surfaces are impossible to get an accurate measurement from without a modification to your IR Thermometer. What actually ends up happening is that you measure the surface temperature of the glass plate that protects the sensor housing of your IR Thermometer. Simply said, you are measuring the temperature of your IR Thermometer, because you are essentially looking at your temperature probe in a mirror. There are special glass coverings that can be used to do this, but don't look for it in a low end IR Thermometer.
Depending on the manufacturer, EMF could play havoc on your IR Thermometer. This is obviously true with any electronic device, but nonetheless worth mentioning.

Needless to say, care must be taken with taking temperature measurements, with this device, to ensure the best overall accuracy in your temperature measurements of an object and to keep you from chasing your tail from a false positive.

Conclusion