Para-Tech-Geek talks Investigative Temperature Monitoring

Help me Para-Tech-Geek- what type of temperature measuring device should I choose to conduct my paranormal investigations?

The best and most common ways of measuring ambient area temperatures are with infrared pyrometers, resistance temperature detectors (RTD) and thermocouples (TC).  The choice between them is usually made by determining responses to the following five (5) basic questions:

1.  What are the temperature requirements?

If process temperatures are between -328 to 932 °F (-200 to 500 °C), an industrial quality infrared pyrometer and resistor temperature devices (RTD) type are the preferred option.  Thermocouples (TC) have a range of -180 to 2,320 °C (-292 to 4,208 °F).

2.  What are the time-response requirements?

Infrared and RTD devices should be used to conduct paranormal investigations given it has relatively fast response time to temperature changes—seconds (e.g. 2.5 to 10 s).  Thermocouples have the fastest response time- fractions of a second

3. What are the accuracy and stability requirements?

RTDs are capable of high accuracy and can maintain stability for many years, while thermocouples can drift within the first few hours of use.  Infrared detectors are subject to the type of material and surface condition due to variations in emissivity.

4. What should be used to measure surface temperature of various types of materials?

Portable “gun type” Infrared pyrometer devices respond quickly and should be selected and used  to measure surface temperatures of such things as heating ducts, chairs, windows, doors, etc..

5. Should temperature monitoring be obtained continuously or as needed?

RTD data loggers are an excellent tool to continuously monitor subtle changes in an area’s temperature, and humidity.  Infrared portable “gun type” are used to measure surface temperatures of such things as heating ducts, chairs, windows, doors, etc.

Paranormal Premise

Ghostly theory believes sources of potential energy must be drawn upon in order for kinetic energy to occur.  Meaning, in order for a spirit to manifest itself into an apparition it needs to have a source of power to draw upon.  Sources of energy that can be drawn upon can come from the local environment such as electrical, thermal, or kinetic.  Therefore, the transfer of thermal energy from the environment for a manifestation to occur, a communicating voice, tap, object movement would result in a reduction of temperature as that energy is drawn.  Like a heating furnace being shut off on the coldest night of the year or a lantern battery going dead unexpectedly the heat leaves the area and is replaced by coldness.

Thermometers can be used to measure the environment’s temperature.  It is recommended that temperature – humidity data loggers be used to routinely to capture evidence regularly at set intervals such that subtle changes in the environment can be measured.

Technical Explanation

Temperature measurement may be achieved using several different methods. Most of the methods rely upon measuring some sort of physical property of a working material that varies with changes in temperature. Investigators must be careful when measuring temperature to ensure that the measuring instrument (thermometer, thermocouple, etc.) is actually recording and displaying the same temperature as the thing being measured. Under some conditions heat from the measuring instrument can cause a temperature gradient that causes the displayed temperature to be different from the actual temperature of the region being measured. An extreme case of this effect gives rise to the wind chill factor, where the weather feels colder under breezy conditions than calm conditions even though the temperature is the same. What is happening is that the breeze increases the rate of heat transfer from the body, resulting in a larger reduction in body temperature for the same ambient temperature.

One of the most commonly used devices used to measure temperature is a glass thermometer.   Unfortunately, these are not adequate to measure temperature when conducting a paranormal investigation because they are too slow to respond to subtle or rapid changes in temperature.  Glass thermometer tubes are filled with mercury or another liquid that acts as a working fluid it takes a while for the fluid volume to expand as the temperature rises, or contract as the temperature drops.

Bimetallic temperature measuring devices take advantage of the difference in rate of thermal expansion between different metals. Strips of two metals are bonded together. When heated, one side will expand more than the other, and the resulting bend is translated into a temperature reading by mechanical linkage to a pointer. These devices are portable and they do not require a power supply, but they are usually not as accurate as thermocouples or RTDs and do not readily lend themselves to temperature recording and are therefore not recommended for investigating.  Other types of equipment that can be used to measure temperature changes during our investigations include:

• Thermocouple Sensors (TC)
• Thermistors and Resistance Temperature Detector (RTD)
• Infrared Pyrometer

Thermocouple Sensors

Thermocouple sensors such as the Mel Meter, and the Environment Meter, generally utilize a K connection probe plug to measure temperature. 

Thermocouples (TC) are pairs of dissimilar metal wires joined at least at one end, which generate a net thermoelectric voltage between the open pair according to the size of the temperature difference between the ends, the relative Seebeck coefficient of the wire pair and the uniformity of the wire pair.  TCs are possibly the easiest temperature sensors to use and obtain and are used widely in scientific and industrial applications. They are “simple”, rugged, need no batteries, and measure over a wide range of temperatures. TCs consist of essentially two strips or wires made of different metals and joined at one end. Changes in the temperature at that juncture induce a change in electromotive force (EMF) between the other ends. As the temperature increases the amount of EMF output rises, though not necessarily linearly.

Resistance Temperature Devices (RTD)

Resistance Temperature Devices (RTD) instruments have the ability to continuously record ambient temperatures and humidity at present intervals.  Obtained readings may be downloaded into a computer and graphed using manufacturer supplied software.  A disadvantage of using data loggers is highly dependent upon proper location placement.  Data loggers provide a retrospective view of the collected information is a reliable way of collecting data and can be used to validate any anomalies having occurred within an investigation’s time frame.

Resistance thermometers are constructed in a number of forms and offer greater stability, accuracy and repeatability than thermocouples in some cases.  Resistance thermometers use electrical resistance and require a power source to operate.  Resistive temperature devices capitalize on the fact that the electrical resistance of a material changes as its temperature changes.  Resistance thermometers are highly accurate (design dependent), reliable (low drift), and cover a wide temperature range

Measurement of resistance requires a small current to be passed through the devise under test.  This can cause resistive heating, causing significant loss of accuracy if manufacturers’ limits are not followed.  Mechanical strain on the resistance thermometer can also cause inaccuracy.  The accuracy of the unit also depends upon the amount of lead wire resistance based upon the two, three or four wire design.  The three wire design is sufficient for most applications.  If more preciseness is desired by the investigator then it is recommended that a four wire design be used.  Resistance thermometers are usually made of platinum because of its linear resistance temperature relationship and chemical inertness

Data Loggers

Thermistors are based on resistance change in a ceramic semiconductor; the resistance drops nonlinearly with temperature rise.  Compared to thermistors, platinum RTDs are less sensitive to small temperature changes and have a slower response time.  However, thermistors have a smaller temperature range and are considered more stable.  It should be noted that increased EMF due to poorly shielded or unshielded electrical cabling may cause an individual physically ill effects but it can also result in contaminated temperature measurements due to stray currents leaping between the leads

Infrared Pyrometers

Infrared pyrometers are great for detecting objects that may make the room cooler (drafts) or hotter (heating ducts), and detecting temperature changes in physical objects.

Infrared pyrometers are non-contact temperature measurement devices. They infer temperature by measuring the thermal radiation emitted by a material.  Infrared pyrometers are useful for measuring component surface temperatures.   Infrared pyrometers with a laser beam are typically used by pointing and shooting at the object being measured.  Infrared pyrometers are used to measure temperature where conventional sensors cannot be employed such as moving objects, or non-contact measurements are required because of contamination or hazardous reasons, where distances are too great, or where the temperatures to be measured are too high for thermocouples or other contact sensors.  The most basic infrared pyrometer design consists of a lens to focus the infrared (IR) energy on to a detector, which converts the energy to an electrical signal that can be displayed in units of temperature after being compensated for ambient temperature variation. This configuration facilitates temperature measurement from a distance without actually contacting the object to be measured.

When selecting noncontact temperature measurement instruments, it is necessary to take into account not only the target and its emissivity, but also the surroundings and the intervening atmosphere. Readings obtained can be influenced by color and reflection of the surface it is pointed at.  The critical considerations for any infrared pyrometer include field of view (target size and distance), type of surface being measured (emissivity considerations), spectral response (for atmospheric effects or transmission through surfaces), temperature range and mounting (handheld portable or fixed mount). Emissivity is defined as the ratio of the energy radiated by an object at a given temperature to the energy emitted by a perfect radiator, or blackbody, at the same temperature. The emissivity of a blackbody is 1.0. All values of emissivity fall between 0.0 and 1.0. Most infrared thermometers have the ability to compensate for different emissivity values, for different materials. In general, the higher the emissivity of an object, the easier it is to obtain an accurate temperature measurement using infrared. Objects with a very low emissivity (below 0.2) can be difficult applications. Some polished, shiny metallic surfaces, such as aluminum, are so reflective in the infrared that accurate temperature measurements are not always possible.

The field of view is the angle of vision at which the instrument operates and is determined by the unit’s optics. To obtain an accurate temperature reading the target being measured should completely fill the instrument’s field of view. The infrared device determines the average temperature of all surfaces within the field of view.  If the background temperature is different from the object temperature a measurement error can occur. More accurate readings can be acquired when it is closer to the object being measured.  At a distance of 6 inches you will be roughly measuring a spot size of about one inch- the further away you are the wider the spot size.

The pyrometer can be either mounted or portable. Fixed mounted units are generally installed in one location to continuously monitor a given process. They usually operate on line power, and are aimed at a single point. The output from this type of instrument can be a local or remote display, along with an analog output that can be used for another display or control loop. Handheld infrared thermometers are one of the most popular types of infrared pyrometer. They are commonly used for portable applications although some models also feature an integral tripod mount. Battery powered, portable infrared ‘‘guns’’ units have all the features of the fixed mount devices, usually without the analog output for control purposes. Generally these units are utilized in maintenance, diagnostics, quality control, and spot measurements of critical processes.

Conclusion

Temperature measurement may be achieved using several different methods. Most of the methods rely upon measuring some sort of physical property of a working material that varies with changes in temperature.

Written By: DGH President, John R. O’Neil