# Q&A

## Can objects of the same material but different colors be measured?

### Yes. In principle, errors caused by color will not occur.

The difference in color of objects occur when the object surface absorbs light from the visible region and diffuses the rest. It becomes blue if blue wavelength light is diffused and becomes red if red wavelength light is diffused. Moreover, it turns black if all the light in the visible region is absorbed and turns white if it all gets diffused.

The radiation thermometer measures light wavelength in the infrared domain and not light wavelength in the visible region. Therefore, in principle, errors caused by color will not occur. However, emissivity may slightly differ depending on the pigment material such as paint.

## Can it be used to measure the temperature of air?

### No, temperature of air cannot be measured.

Air cannot be measured because infrared radiant energy is very small. Therefore, it means that air hardly absorbs infrared rays. Due to this characteristic, the temperature of the measuring object can be measured by transmitting infrared rays radiated by objects placed separately in air. (Kirchhoff`s Law)

What happens if the clear sky is measured?

It will over range the lower measuring limit. This is because very little infrared energy are radiated from space (some are absorbed in the atmosphere) and small amounts of radiant energy from the atmospheric layer are measured.

## Can it be used to measure water temperature?

### It is possible to measure the surface temperature of water. When stirred, the temperature difference between the surface and under the surface is minimal, enabling highly accurate measurements.

Temperature difference occurs between the surface and the center in the following situations below.

Temperature difference occurs internally in boiling water in pans and etc., due to the natural convection phenomenon where warm water moves upwards. Therefore, depending on the places compared, the surface temperature may turn out to be higher than under the surface.

The temperature of the surface becomes lower than under the surface if it is just before boiling. This is because the amount of vapor generated from the surface increases rapidly and a large amount of vaporization heat is deprived.

Moreover, in situations where there is steam from the surface, measurement error increases due to the influence of infrared scattered by it.

## Can it be used to measure transparent plastic?

### Thick plate-like plastic that have high emissivity can be measured.

As mentioned in “Can objects of the same material but different colors be measured?”, radiation thermometers measure wavelength of light in the infrared region and not in the visible region. So whether objects can be measured or not is not related to transparency (color).

The problem is whether plastic is transparent or opaque in the infrared region. If it is opaque, absorptivity and emissivity are high so measurement is possible.

As there are many types of plastic, emissivity also varies. Thin plate-like and sheet-like plastic have low emissivity, some of which cannot be measured. (polyethylene, polypropylene and etc.) However, even with same type of plastic, block-like and thick plate-like plastic can be measured due to its high emissivity.

## How far objects can be measured?

### Distance does not matter. As long as there are no substances blocking the infrared rays emitted from the measuring object, measurement is possible. However, the field of view of the radiation thermometer (relation with target size and measuring distance)

Measurement with radiation thermometers are possible as long as there are no substances blocking the infrared rays emitted from the measuring objects. However, the size of the target differs depending on the distance to the measuring target. The further the wider field of view, a wider range of temperature will be measured so the field of view may extend to the surroundings of the measuring object. Therefore, even when far apart, the measuring object can be measured accurately if the size is bigger than the target size of the radiation thermometer.

## Does high frequency or magnetic force affect measurement?

### It is recommended to measure objects with relatively stable temperature such as the floor surface before actual measurement to check that malfunction does not occur.

Countermeasures against influences of normal radio waves are taken but high electromagnetic fields may cause not only indication error and CPU malfunction but also breakdowns. If the object size is big, malfunction can be avoided by increasing the distance from the radiation thermometer. It is recommended to measure a relatively stable temperature such as the floor surface before measurement so that malfunction does not occur.

## Which is more highly accurate, contact or non-contact radiation thermometers?

### For measuring the surface temperature, radiation thermometers can often measure more accurately in situations as below.

As radiation thermometers measure the surface temperature of the object in principle, below is a chart when comparing with contact types.

Large errors caused by contact area may occur with contact type thermometers. It is difficult to get the correct value for materials with low heat capacity such as paper as the temperature changes due to contact. Moreover, the same goes for situations when there is not enough time for the temperature sensor and object to be in thermal equilibrium, in situations such as when the object is being heated or cooled. As radiation thermometers measure infrared energy at high speed, substances with small heat capacity or objects when the temperature is changing can be measured highly accurately.

Contact type

Non-contact type

Rubber

Water

Film

Plastic

Food （surface）

Food（inside

Electronic circuit

Metal

## Can it be used to measure metal?

### They can be measured by using blackbody tape or blackbody spray.

It is generally said accurate measurement is difficult as metal has low radiant energy in the low temperature region. It is recommended to use blackbody tape or blackbody spray for measurement. But, the heat resistant temperature of the blackbody tape is less than 180 degrees and the blackbody spray is less than 300 degrees.

## Can it be used for maintenance and inspection of equipment’s?

### IT-545 series with alarm functions is recommended.

It is important to quickly detect abnormal temperature caused by contact failure of electric equipment`s such as switchboards.

IT-545 series has a function where the alarm goes on when the temperature exceeds the reference temperature. Working efficiency will improve because the temperature does not need to be checked upon on.

## Can it be measured through glass?

### It is recommended to use barium fluoride windows (option) instead for measurement.

Quartz glass that are used generally absorb light with wavelength longer than 2.5μm.

HORIBA`s radiation thermometer cannot be measured through glass because it measures light with wavelength longer than 2.5μm and measures the surface temperature of the glass instead.

It is recommended to use barium fluoride windows instead of glass for measurement.

## Can it be used to measure the inner part of a vacuum chamber?

### Measurement is possible as infrared rays permeate vacuums. However, when performing actual measurements, please use a barium fluoride window for the chamber window material.

Measurement is possible as infrared rays permeate vacuums. However, when performing actual measurements, please use a barium fluoride window for the chamber window material.