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FAQ's
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. Thermocouple type 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)
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)
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)
Note: The ratio of distance between
target and sensor to target size is
called Field Of View (FOV).
 |
1" (1:1) |
3" (3:1) |
5" (5:1) |
|
10" (10:1)
|
|
Target
Size - 1"
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).
| AMBIENT
TEMPERATURE RANGE |
RECOMMENDED MODELS
|
| |
|
| 32 - 160F (0 -
70C) |
IRt/c.01, IRt/c.03 |
| 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
HOW DO I CALIBRATE MY IRt/c?
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 www.exergen.com
for all IRt/c models.
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.
| MODEL |
MINIMUM SPOT SIZE |
UP TO DISTANCE (inches) |
| |
|
|
| 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.
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