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FAQ -Others
How Infrared Thermometer works?

Infrared thermometers measure the surface temperature of an object. The unit's ooptiocs sense emitted, reflected and transmitted energy, which are collected and focused onto a detector. The unit's electronics translate the information into a temperature reading display on the unit. The lasers are used for aiming purpose only.

Some IR thermometers use lasers. Do they take temperature readings? Are they dangerous?

No on both questions. Lasers are used only for aiming or sighting. The lasers are low voltage units and are not dangerous. Note, however, that all lasers have government regulated labels on them stating power ratings and any necessary safety measures (usually "do not stare into beam").

Can I measure the body temperature of an Ant by IRT?

You can pointing the IRT to an Ant on your desk, but what you get is an average temperature of the Ant & the Desk because the Field Of View of the IRT is much larger than the Ant.
But, if you can get 10,000 of ant, on your desk, which can cover the whole FOV of the IRT,then YES, you can measure the body temp of Ant.
This FOV issue, is a key to get correct reading from IRT.

As I remember, usually IRT are much larger than this one? Accuracy is compromised?

IRT were much larger, but ZyTemp is as small as the "battery of some large IRT".
Accuracy is not compromised, each device has a test report in our database, which is traceable by the serial number.
These test follow the disciplines of "ASTM E1256.Test Methods for Radiation Thermometers (Single Waveband Type)"

Under Development:
COC on Web
You can check the accuracy test report of the very IRT in your hand by visiting our web site www.ZyTemp.com and entering the serial no.
Some model (TN1xx-tr) has a hardcopy test report right in the package.
RII is the only manufacturer who can provide free test report via internet.
In terms of accuracy, size doesn't matter.

Can IRT measure air temperature?

No and Yes.
No, because Air do not emit infrared, the emissivity is too low to be detected.
Yes, because you can pointing the IRT to anything that has the SAME temperature as the air:
Outdoor: leaf , tree, grass (under sunshade) has the same temperature as the air
Indoor: your desk, a piece of paper, has the same temperature as the air.
The key to get "Air temperature" is to measure "anything which should have the same temperature as the air"

Can I measure the gas temperature inside a combustor with good precision using an IR-thermometer?

The reading of IR-thermometers are not affected by the gas flow velocity as for contact sensors and the response time is fast. IR-thermometers looking at radiation from particles or the 4.3 µm hot-band of carbon dioxide can usually be used. Two-colour pyrometers based on emitted radiation from particles require high concentration of particle and long path length, i.e. the gas temperature measurement is influenced by the temperature of the opposite wall with too few particles in the field of view. The IR-thermometer based on radiation from a single band of carbon dioxide works well if the temperature profile along the field of view is flat and with a content of 1-12% carbon dioxide of the fluegas (low carbon dioxide concentration requires long path length).

How far can I measure?

Can I measure temperature of a wall from 5 meter? Can I measure temperature of a mountain from 1 km?
We are using the 8um to 15um infrared, the atmosphere is almost totally transparent for this band.
At 100 meter, no rain, no fog condition, IRT is very accurate.
At 1 km, you need some physics background to correct the reading.
see [Theory and Practice of Radiation Thermometry] by D.P. DeWitt, chapter 3.

Can the IRT operated in complete darkness?

Yes, that's why DOD & military are so interested in IR.
In fact, the early IR technology are developed by military fund.

Can the IRT penetrate a building, measure what's inside?

In real life, No. It can be done only in the movie.

But I remember IR can penetrate something?

IR can penetrate PE film (for example: a complete dark garbage bag), Silicon, Gemanium.
You can hide something warm behind a PE film (your hand), the IRT can detect the presence of the object.

Now I can measure the body temperature of a fish in my aquarium?

No, water & glass is transparent for visible light only, but for IR, it's completely "opaque", all IR from the fish can't penetrate the water, so you are only measure the temperature of the glass.
How about my pet's temperature? by pointing IRT to your dog, you get the temperature of the fur. What you see is what you got.

How do I know, my IRT is still accurate?

Calibration of IRT is extremely sophisticated, that's why IRT were so expensive. (not any more!)
RII develop his own proprietary CCE(Continuous Calibration Equipment), which can calibrate 96pcs of IRT at the same time, at different temperatures, in a continuous, high throughput operation.
The Cycle time is also reduced by a special prediction algorithm.
RII are ISO9001 certified.
Our Infrared Ear Thermometer can conform with the ASTM E1965's stringent requirement: +/-0.2°C
If still in doubt, you can try this DIY-Calibration:

  1. Fill a large polystyrene (e.g., Styrofoam) cup (10 oz or larger) (or any Thermos) halfway to the surface with crushed ice.
  2. Add cold tap water to ? to 1 inch below the rim of the cup tip. Two cups, one inside the other, will provide better insulation and more stable temperatures throughout the test.
  3. Immerse the tip of an accurately calibrated contact probe thermometer, that has been calibrated, into the water and vigorously stir the water's surface with the probe for one minute, or until contact probe temperature stabilizes.
  4. When the probe temperature has stabilized, continue stirring the water, while taking simultaneous temperature measurements with the IR thermometer.
  5. Hold the IR thermometer within 1 inches of the surface of the water for the most accurate measurement. Infrared temperature
    measurement should be within +/-1˘J (+2°F) of probe reading at 0°C(32°F).

Warning: because such a testing requires special technique; and for the follow reason, RII has no guaranty on the result.


Advanced user may use a home made triple-point (liquid; gas and solid co-exist) to calibrate your Contact Thermometer,
see Scientific American, January 13, 1999, "Tackling the Triple Point", By Shawn Carlson
This article provides an innovative way to maintain a temperature standard about 0.0001 °C, right in your home and costs less than $50 to build.
Triple-point of water is a very accurate temperature standard, much better than "Ice &Water coexist".

What else can I use IRT to measure?

You can measure the temperature of almost anything, including the universe! to prove the Big Bang theory.
In 1965, the remnant radiation from the Big Bang was discovered by radio astronomers Arno Penzias and Robert Wilson. This radiation, which peaks at 3 K (-270°C) can be found in all directions in space.
Such a temperature is an evidence of the Big Bang (the origin of this universe).
Well , you have to carry an IRT to outer space to get a correct reading. Well, of course, you need some sophisticated IRT and maybe a space shuttle to do this measurement.
Our IRT still can't operate in outer space.

So this "Swiss Army Thermometer" can measure anything?

Yes, it's a Swiss Army Thermometer. But there are still something impossible to measure :
Gold, Shining Metal, or any low emissivity material.
For example: the reading of a 125°C gold, is only about 27°C.
For these material with high reflection in IR, what you are measured is only the REFLECTION.
When IRT fail, try other contact type thermometers
Find..List..Learn About Temperature Sensors at: www.temperatures.com

Hint to get accurate reading with IRT?

The target must cover the whole FOV(Field Of View) of the IRT.
Avoid shining surface(metal), rough surface give better accuracy.
add Electrical Insulating Tape (black is better) on the metal surface, can solve the problem, give accurate result.
be sure the tape is large enough to cover to Field Of View of the IRT.
be sure the tape will not BURN. use with caution!
Avoid temperature noise (avoid other High temperature object is nearby)
for example: you are measuring an IC, with a solder-iron nearby
Try to perpendicular to the target surface.

Which surfaces behave like a grey body?

In practice none!  The emissivity is independent of wavelength for a grey body. The emissivity of all real surfaces changes with wavelength, although some surfaces are close to a grey body. The ideal gray body concept is useful for simplified equations in heat transfer calculations.

I am using a radiation thermometer to measure the temperature of a sample, but I am getting different results compared with using a thermocouple immersed in the sample?

There are a number of possible reasons for the difference, in addition to possible calibration errors. Firstly, the thermocouple might not be in good thermal contact with the surface of the sample, or there might be temperature gradients within the sample. If this is the case then the thermocouple and radiation thermometer will not be measuring the same temperature. Alternatively, if the emissivity of the sample is low, or not precisely known, the temperature measured by the radiation thermometer will not represent the true temperature of the sample, again leading to differences. Also, if the sample is small, it might not be fully filling the field-of-view of the radiation thermometer, and the radiation thermometer temperature will therefore be low compared to that of the thermocouple.

Can I use an anodised aluminium plate or a tungsten ribbon lamp, rather than a blackbody source, to calibrate my radiation thermometer?

Firstly, the calibration source needs to have a high and accurately known emissivity to ensure that measured temperature will accurately reflect the true temperature of the surface. Secondly, the source needs to be large enough to fill the optical field-of-view of the radiation thermometer, since underfilling the field-of-view will result in measurement errors. Thirdly, the temperature of the source needs to be measured by some means, for example by using a contact sensor inserted close to the radiating surface. A blackbody source with an aperture of a suitable size meets these requirements and should therefore usually be used to calibrate radiation thermometers. The use of an anodised aluminium plate is not generally recommended for checking or calibrating radiation thermometers. Firstly, the emissivity of anodised aluminium is quite low and depends on the thickness of the anodised layer. Many radiation thermometers operate at wavelengths in the infrared, and in this region the emissivity can be anywhere between 0.9 and 0.4. The actual value must be known if measurement errors are to be avoided. Secondly, because the emissivity is low, the radiation measured by the thermometer will be a combination of radiation emitted by the plate and radiation reflected from the plate from other objects in the room. This will, again, lead to potentially significant errors in the reading. Thirdly, there must be some other means, such as a contact probe, for determining the temperature of the plate. If this probe is not in good thermal contact with the plate, or if there are temperature gradients across the plate, it will not give a good indication of the true plate temperature. It will therefore not be possible to accurately check the calibration of the radiation thermometer. Tungsten ribbon lamps can be used for calibrating some types of radiation thermometer. However, they suffer from a number of potential drawbacks. Firstly, the filament is very narrow: typically 1.5 mm, although lamps with 3 mm wide filaments are also available. This is generally too small to fill the field-of-view of most modern, commercial radiation thermometers and will lead to significant measurement errors. In addition, the emissivity of the tungsten filament is low (about 0.4), and varies with both temperature and wavelength, and the transmission of the glass envelope also varies with wavelength. Since the lamp is calibrated in terms of radiance (apparent, or brightness) temperature at a precise wavelength (usually around 650 nm - 660 nm) these effects can be neglected provided that it is only used to calibrate radiation thermometers that operate at that wavelength. However, radiation thermometers which do not operate over such a narrow and precise wavelength band cannot be calibrated using lamps.

What is a blackbody source and what is it used for?

A blackbody source is an ideal, 'Planckian', radiator, i.e. it emits thermal (visible and infrared) energy whose intensity at a given wavelength and temperature is given by the Planck Law of radiation. Blackbody sources, whose temperatures are known or can be measured, are therefore extremely useful standards for the calibration of radiation thermometers. An ideal blackbody source is a completely enclosed cavity held at a uniform temperature. The radiation field inside the cavity depends only on the temperature, and not on any physical property (size, shape, construction material). It completely absorbs and emits all radiation and has an emissivity of 1. For practical purposes, in order to view the radiation field inside the cavity, it is necessary to introduce a hole or aperture. Since this means a departure from the 'ideal' situation it is not possible to have a practical blackbody cavity with an emissivity of 1. However, by careful design cavities can be made with emissivities that closely approach 1.

Founded in July 2000, ZyTemp belongs to world-class Infrared Technology-oriented thermometer manufacturer - Radiant Innovation Inc. and become a premier provider of infrared temperature measurement devices. Originally started from a professional team of engineers specializing in infrared thermometry, this company is now emerging as worldwide well-known manufacturer of infrared thermometers (IRT).

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