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Exergen Corporation provides educational materials on infrared thermometry through these education centers. 
We invite you to return regularly to learn more as we continue to develop this area of our site. 

Through the Looking Glass: Alices Quest for Emissivity
Articles by Exergen President Francesco Pompei Ph.D.
Industrial Division PowerPoint Presentations
Articles by Exergen President Francesco Pompei Ph.D.

A case for the unpowered IR thermocouple: June 1995 issue of I&CS, Special Report on Temperature Control. Click here.

A Certified Emissivity Blackbody for Calibrating Infrared Thermometers: Sensors On-line-April 2002. Click here.

Aspects of increased production speeds via IR control of product internal temperature: Electricity + Control/May'02. Click here.

Inside & Out: Increasing Production Speeds via IR Control of Product Internal Temperature: April 2003 issue of Intech/ISA. Click here. 

Hunting Mighty Milliwatts: 7x24 Exchange, June 5, 2006. Click here.

Industrial Division PowerPoint Presentations
INDUSTRIAL DIVISION SLIDE SHOW: Company Profile, IR theory, Industrial Product background, Applications
Speed Boost System: Learn how to utilize IRt/c's to increase production line speed with this NEW TECHNIQUE!
What is an IRt/c?
The IRt/c is a patented Infrared Thermocouple. It is a self powered sensor that emulates a thermocouple within specified temperature ranges and provides a predictable and repeatable signal outside that specified range. With programmable input devices, the mV signal output tables are available to download. The infrared technology allows you to measure product temperature without touching the product. It also allows for a very fast reading (~ 100 msec response time).
Will the IRt/c be wired like a thermocouple?
Yes, the red wire is negative just like a t/c. But, you must pay attention to leakage current issues. As the IRt/c has higher impedance than your conventional t/c. (3 - 16 kohms compared to <100 ohms), it is recommended to use input devices with leakage current < 10 nA. If that is not possible, then the input device, should be one that allows enough offset to compensate for leakage current. As a general rule, the smaller the offset the better.

What is the standard cable length of an IRt/c?

3 feet of thermocouple wire (J, K, etc.) is the standard length. Other cable lengths are available for an additional charge.
How do I select which IRt/c is suitable for my application?
What you need to know are the following:
  1. Target Size
  2. Distance between target and sensor
  3. Target temperature range
  4. Ambient temperature range (where sensor is located)
  5. Output desired
  6. Dusty/dirty environment?

If the ratio of the distance between target and sensor to target size is <1:1, then any 1:1 model can be selected (IRt/c.01, IRt/c, IRt/c.1X, IRt/c.SV).
If the ratio of the distance between target and sensor to target size is <3:1, then any 3:1 model can be selected (IRt/c.03, IRt/c.3X, IRt/c.3SV, SmartIRt/c.3)
If the ratio of the distance between target and sensor to target size is <5:1, then the 5:1 model must be selected (IRt/c.5, SmartIRt/c.5)
If the ratio of the distance between target and sensor to target size is <10:1, then the 10:1 model must be selected (IRt/c.10)

If the ratio of the distance between target and sensor to target size is <20:1, then the 20:1 model must be selected (IRt/c.20A or SmartIRt/c.20)
Note: The ratio of distance between target and sensor to target size is called Field Of View (FOV).

The IRt/c.01 and IRt/c.03's are ABS plastic models, not recommended for rugged industrial applications. The IRt/c, IRt/c.1X, IRt/c.SV are all stainless steel with no air purge for cleaning or cooling. The IRt/c.3X, IRt/c.3SV, IRt/c.5, and IRt/c.10's have built in air purge for cooling and cleaning. If the ambient temperature is >160F (70C), then ABS plastic models can not be used. For ambient temperatures from 160 - 185F (70 - 85C), the stainless models can be used without any air. If the ambient is >185F (85C) and < 240F (115C), then the IRt/c.3X or IRt/c.3SV will do. For ambients >185F (85C) and <400F (204C), the IRt/c.5 or IRt/c.10 will work. There are also cooling jackets available for IRt/c, IRt/c.1X, and IRt/c.3X that will cool with air up to 700F (371C) and water up to 1000F (538C).
32 - 160F (0 - 70C) IRt/c.01, IRt/c.03, SmartIRt/c
32 - 185F (0 - 85C) IRt/c, IRt/c.1X, IRt/c.SV
32 - 240F (0-115C) IRt/c.3X, IRt/c.3SV
32 - 400F (0 - 204C) IRt/c.5, IRt/c.10
32 - 700F (0 - 371C) IRt/c, IRt/c.1X, IRt/c.3X with CJK-1 air cooling jacket
32 - 1000F (0 - 538C) IRt/c, IRt/c.1X, IRt/c.3X with CJK-1 water cooling jacket
Since the IRt/c is designed to emulate a conventional t/c over a specific temperature range, the target temperature range must be selected from the selection table below:
So the complete part is: IRt/c - MODEL DESIGNATION (*) - THERMOCOUPLE TYPE (**, J, K, etc) - TEMPERATURE RANGE
There are two things that need to be calibrated for with the IRt/c.
1. LEAKAGE CURRENT - The IRt/c has higher impedance than the conventional t/c. And every input device has a certain amount of leakage current. The recommended leakage current for an input device is < 10 nA. If it is higher, than an offset will be needed. To calibrate for leakage current, blind the sensor (cover the sensing eye with foil). Record the temperature. Then short out the input (wire the + and - together) to the input device. This will give you the cold junction input temperature. The difference in temperature is your offset. Adjust in the input device by using the OFFSET, CAL LOW, or ZERO function.
2. EMISSIVITY - A target's ability to emit energy compared to a blackbody is called emissivity. The IRt/c is calibrated on targets with an emissivity of 0.9, and in ambient blocks that simulate real world conditions. Every target will have a different emissivity, so a calibration must take place to compensate for emissivity. First thing to do is measure the target's true temperature with a reliable reference (Exergen's D or DX Series thermometer on a non-metal or coated metal target). Record that temperature. At the same time aim the IRt/c at the target. Adjust the input device by using the GAIN, CAL HIGH, or SPAN in the input device to match the reference.
This is what's called a 2 POINT CALIBRATION. If your input device only has the capability to do just the OFFSET, you should do a ONE POINT CALIBRATION at the target's control temperature.

Can I use my IRt/c outside of its linear range (for example, can I use an IRt/c-K80F at 500F)?

Yes, but you will need a programmable input device. The mV signal output is predictable and repeatable outside of its linear range. So with a programmable input device the mV signal tables can be downloaded. Some examples of programmable input devices are the Eurotherm Controllers and Applied Technology Concepts Smart Transmitters. If you have a programmable input device, the mV signal output tables are available at for all IRt/c models.

The SmartIRt/c's are also designed to be linear over wider temperature ranges.

What makes the IRt/c better than other Infrared Temperature Sensors?

The main features of the patented IRt/c are it's:
Self powered - The World's only self powered infrared temperature sensor
Instrinsically safe - With its self powered feature, there is no energy stored, which makes it intrinsically safe

Calibrated to real world conditions for real world performance accuracy (see Tech Notes 89 and 90) - Other infrared sensors are calibrated to blackbody sources, with no compensation for ambient temperature errors, the IRt/c compensates for changes in ambient conditions

Can I measure a spot that is 0.1" with a 3:1 sensor at 0.3"?
No, each IRt/c has a minimum spot size, the minimum spot size of each sensor is listed below. You can not measure a target smaller than the minimum spot size.

uIRt/c 0.1" 0.05"
uIRt/c.4 0.1" 0.4"
SmartIRt/c.3 0.12" 0.3"
SmartIRt/c.5 0.12" 0.5"
SmartIRt/c.20 0.625" 12"
SmartIRt/c.40 0.625" 24"
IRt/c.01 0.3" 0.3"
IRt/c 0.3" 0.3"
IRt/c.1X 0.3" 0.3"
IRt/c.SV 0.3" 0.3"
IRt/c.03 0.25" 0.75"
IRt/c.3X 0.25" 0.75"
IRt/c.3SV 0.25" 0.75"
IRt/c.5 0.80" 4.0"
IRt/c.10 0.80" 8.0"
IRt/c.10A 0.80" 8.0"
IRt/c.20A 0.80" 16.0"
IRt/c.100A 0.80" 80.0"
IRt/c.2ACF 0.11" 1.7"
IRt/c.2/15ACF 0.11 x 0.35" 1.7"
IRt/c.4ACF 0.20" 1.7"
IRt/c.8ACF 0.33" 1.7"
IRt/c.2/18AMF 0.18 x 0.5" 3.0"
IRt/c.3AMF 0.15" 3.0"
IRt/c.6AMF 0.26" 3.0"
IRt/c.12AMF 0.48" 3.0"
IRt/c.2/15ALF 0.12 x 0.28" 4.1"
IRt/c.4ALF 0.14" 4.1"
IRt/c.7ALF 0.28" 4.1"
IRt/c.2AXLF 0.07" 8.0"
IRt/c.4AXLF 0.19" 8.0"
IRt/c.10/38AULF 0.40 x 1.5" 10.0"

What happens when my target is smaller than my spot size?

The IRt/c will measure the average amount of energy within that spot, including the background. So if the background is a lower temperature, the sensor will read lower. If the background and the spot size is constant, then the error can be calibrated out for, using the same calibration method as used for emissivity.
How do I measure a low emissivity target with an IRt/c?
Ideally, you want to condition the surface to be measured (paint, coat, oxidize, lubricate, etc). That will increase the surface's emissivity and give the sensor more energy to measure. If that can not be done, there are adjustable LoE models that can be used at higher temperatures (starting at about 300F). If it is a low temperature, low emissivity target, a precalibrated model with an input device that can adjust for a high gain can be used, and a reflective shield between the sensor and target helps. The SmartIRt/c's can also be calibrated for low emissivity materials.


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