Choosing and Using a Digital Thermometer
I’m writing this article to clarify the difference between two different types of digital thermometers that are commonly used in
paranormal investigations and how to properly use them. If you are like me when you were looking for that first digital
thermometer, you had to choose from an infrared or an ambient type. Is there a difference? You betcha! Let’s discuss both
types.
The first type I’ll mention is the non-contact digital thermometer. This type emits an infrared beam that measures temperature on
any given surface. Some models have a laser to help you see what you’re measuring. They are more than accurate enough for
paranormal investigation use but just remember that you are measuring surface temperature not air temperature. I have read
articles from paranormal investigators that claim that IR thermometers can read ambient air temperature even though the
manufacturers of these devices say they can’t so this is a debatable point. The good thing about the non-contact type is that
they can be very inexpensive. I’ve got one I paid 15 dollars for and it works fine. The beam that they emit has a particular
“distance to spot size” (D:S) as it hits the target surface. The temperature read is the average of the spot. If you hit a curtain
and a refrigerator with the same spot you will get the average temperature reading of both items within that spot. The closer
you get to the surface the smaller the spot measuring the temperature is. This spot size is also determined by the specifications
of the thermometer. For a thermometer with an 8:1 D:S if you are standing 8 feet away from the target surface the spot diameter
will be 1 foot. You also need to make sure that you know what the maximum working distance is for your thermometer.
Non-reflective surfaces will yield a more accurate reading than reflective ones. This brings me to a drawback to this type of
thermometer. If you aim the beam at a window the beam will continue though the window and give you the temperature of a
surface that lies on the other side of that window (unless it reflects off the window and then may not be accurate). If you target a
wall that has a heater unit behind it you may get a warmer reading than that of the room’s air so be aware of any hot or cold
influences around your target area.
The second type I’d like to talk about is the ambient type thermometer. This type in my opinion is the better choice for
paranormal investigations because it measures the ambient air temperature. When you get a “cold spot” you can place the
thermometer or probe in the spot and get the actual reading of the air in that spot. If you use an infrared type you can only read
a surface that is affected by the “cold spot”. Some of these ambient types use what is called a “K type” probe that is plugged
into the device. The probes on these units are what sense the air temperature. These probes are actually thermocouples. A
thermocouple contains materials that vary the resistance of the electrical signal, based on the temperature they sense, and
sends this signal to the thermometer that gives you a temperature reading. With the “K type” thermometer you can get
temperature readings at the thermocouple and some of them allow you to get a differential reading between the thermometer
and the thermocouple. This can be useful if you wish to check the difference of temperature at one location and another at the
same time. Of course the two locations would have to be pretty close to each other. Some thermometers boast high accuracy
and some fast response time, I would recommend for investigations using one with a fast response time because you don’t know
how long that “cold spot” is going to be there.
I hope this article helps you in choosing a digital thermometer. The better suited our equipment is, the better results we will
obtain.
I’m writing this article to clarify the difference between two different types of digital thermometers that are commonly used in
paranormal investigations and how to properly use them. If you are like me when you were looking for that first digital
thermometer, you had to choose from an infrared or an ambient type. Is there a difference? You betcha! Let’s discuss both
types.
The first type I’ll mention is the non-contact digital thermometer. This type emits an infrared beam that measures temperature on
any given surface. Some models have a laser to help you see what you’re measuring. They are more than accurate enough for
paranormal investigation use but just remember that you are measuring surface temperature not air temperature. I have read
articles from paranormal investigators that claim that IR thermometers can read ambient air temperature even though the
manufacturers of these devices say they can’t so this is a debatable point. The good thing about the non-contact type is that
they can be very inexpensive. I’ve got one I paid 15 dollars for and it works fine. The beam that they emit has a particular
“distance to spot size” (D:S) as it hits the target surface. The temperature read is the average of the spot. If you hit a curtain
and a refrigerator with the same spot you will get the average temperature reading of both items within that spot. The closer
you get to the surface the smaller the spot measuring the temperature is. This spot size is also determined by the specifications
of the thermometer. For a thermometer with an 8:1 D:S if you are standing 8 feet away from the target surface the spot diameter
will be 1 foot. You also need to make sure that you know what the maximum working distance is for your thermometer.
Non-reflective surfaces will yield a more accurate reading than reflective ones. This brings me to a drawback to this type of
thermometer. If you aim the beam at a window the beam will continue though the window and give you the temperature of a
surface that lies on the other side of that window (unless it reflects off the window and then may not be accurate). If you target a
wall that has a heater unit behind it you may get a warmer reading than that of the room’s air so be aware of any hot or cold
influences around your target area.
The second type I’d like to talk about is the ambient type thermometer. This type in my opinion is the better choice for
paranormal investigations because it measures the ambient air temperature. When you get a “cold spot” you can place the
thermometer or probe in the spot and get the actual reading of the air in that spot. If you use an infrared type you can only read
a surface that is affected by the “cold spot”. Some of these ambient types use what is called a “K type” probe that is plugged
into the device. The probes on these units are what sense the air temperature. These probes are actually thermocouples. A
thermocouple contains materials that vary the resistance of the electrical signal, based on the temperature they sense, and
sends this signal to the thermometer that gives you a temperature reading. With the “K type” thermometer you can get
temperature readings at the thermocouple and some of them allow you to get a differential reading between the thermometer
and the thermocouple. This can be useful if you wish to check the difference of temperature at one location and another at the
same time. Of course the two locations would have to be pretty close to each other. Some thermometers boast high accuracy
and some fast response time, I would recommend for investigations using one with a fast response time because you don’t know
how long that “cold spot” is going to be there.
I hope this article helps you in choosing a digital thermometer. The better suited our equipment is, the better results we will
obtain.
Mark Sentelle Sr.
A.P.I.
1-19-2009
A.P.I.
1-19-2009
This is a picture of a test Mark and Ben were performing to test the distance ratio on the infrared digital
thermometers. We tested the temperature reading at various measured distances with the refrigerator door
open and then closed, and then recorded the temperature readings as the aspect ratio expanded. This test
can confirm that your thermometer is calibrated to the correct ratio that is stated on the product specifications.
This test can be performed to evaluate cold temperatures (refrigerator) or hot temperatures (kitchen oven). We
suggest testing your equipment to verify that it meets the standards as specified by the manufacturer.
thermometers. We tested the temperature reading at various measured distances with the refrigerator door
open and then closed, and then recorded the temperature readings as the aspect ratio expanded. This test
can confirm that your thermometer is calibrated to the correct ratio that is stated on the product specifications.
This test can be performed to evaluate cold temperatures (refrigerator) or hot temperatures (kitchen oven). We
suggest testing your equipment to verify that it meets the standards as specified by the manufacturer.