Infrared Temperature Controller

infrared temperature controllerThe sensors are non-contact measuring infrared temperature type. They calculate the surface temperature based on the emitted infrared energy of objects. An integrated double laser aiming marks the real measurement spot location and spot size at any distance on the object surface.

The RDO Induction system features a non-contact Infrared temperature controller with laser sighting for metal processing and measurements of metal oxides and ceramics. It is compatible with all our RDO Induction power supplies. The IR sensor is mounted on a stand and can be swiveled 360° to position the sensor head in the desired exact location. The sensor measures range from 50°C up to 2200°C.


Infrared Temperature Controller Features

infrared controller

  • 1μm, 1.6μm or 2.3μm measuring wavelength for accurate temperature measurements in difficult emissivity conditions
  • Response time of 1ms 
  • Double laser marks exact spot size from 0.45mm
  • Optical resolution of 300:1 or 60:1 with selectable focus
  • Up to 85°C ambient temperature without cooling, automatic laser switch-off at 85°C, up to 315°C with water-cooled housing
  • Selectable analog output, optional digital interfaces

Measurement Specifications

Temperature Range  Spectral Range   Optical Resolution
 650-1800°C  1.0 μm 300:1
 800-2200°C  1.0 μm 300:1
 385-1600°C  1.6 μm 300:1
 490-2000°C  2.3 μm 300:1
 50-400°C  2.3 μm 60:1
 100-600°C  2.3 μm 100:1
 150-1000°C  2.3 μm 300:1
 200-1500°C  2.3 μm 300:1
 250-1800°C  2.3 μm 300:1

Temperature Measurement with RDO IR Temperature Controller

Large Temperature Measuring Range

The RDO infrared temperature sensors are suitable for use across a wide measuring range, from moderately low power heating temperatures like curing or tempering to the highest temperatures in hot melting materials or blast furnaces. This portable, hand-held product measures these temperatures precisely. They are designed to measure temperatures from 50°C to 2200°C (122°F to 3632°F). The infrared radiation emitted by a body is used for measurements. As this measurement is a non-contact technology, the devices perform wear-free and can therefore be reliably used in the long term. This temperature controller is used in a wide range of applications, from factory automation, R&D to process monitoring.

Precise and Stable Measurements

High accuracy and resolution are the key characteristics of RDO IR temperature sensors. Particularly, with temperature-critical applications, RDO IR sensors are the preferred choice for easy and precise measurements.


The measurement spot size with the desired working distance is a critical factor. In order to enable the ideal choice for any application, a large number of different lenses is available. These differ with respect to the relation between the target distance and the spot diameter.

SF lenses (Standard Focus) have an almost linear relation while the CF lenses (close focus) have a smaller measurement spot in sensor-close distances. FF lenses (Far Focus) are especially suitable for large distances from measurement object with a comparatively small measurement spot.

SF,CF & FF lens

Detection of Smallest Measurement Objects

Often, conventional IR sensors cannot detect tiny, temperature-critical parts e.g. on chips and circuit boards. Due to the comprehensive range of optical systems, even smallest measurement objects < 1mm (0.04”) can be detected precisely. 

How Does Infrared Temperature Measurement Work?

Because of the internal movements of the molecules inside any object, an infrared radiation is emitted to the surrounding atmosphere. The intensity of this movement depends on the temperature of the object. Under the effect of molecules movement, electrical charges inside the material shake at a very high frequency. This will result in electromagnetic radiation from the material. The radiation is in the form of light (photon emission). The wavelength of these radiations is between 0.7μm to 1000μm, which according to the following graph is within the red area of visible light. However, since a naked eye cannot see this range of wavelength, it is called “Infra-red”. 

Electromagnetic Spectrum Diagram

When a part reaches high temperatures (above 600°C/1112°F), it starts to emit the radiation in the visible wavelength range. This is why human eye can detect when the objects get hot and start glowing from red to white.

An Infrared Temperature Controller works according to the principles of human eyes. According to the figure below, the infrared radiation from an object passing through the surrounding atmosphere and the lens of the controller is received by the photo-sensitive electronic system inside the device. Then the received energy is converted into signals to be interpreted as measuring temperature in the controller.

infrared radiation pathway

The amount of the infrared radiation emitted by an object is measured by the IR Controller. The IR radiation increases as the temperature of the object raises.


The relation between the power emitted from an object and that of a blackbody is called Emissivity, ε, and can have maximum value of 1 (for an ideal blackbody) and minimum of 0 for a perfect reflector. The objects are categorized according to their emissivity as follows:

  • Blackbody: ε=1;
  • Gray bodies: 0 < ε < 1;
  • Non-gray bodies: 0 < ε < 1 and ε is dependent on temperature and wavelength, e.g. glass and metal;
  • Ideal reflector: ε=0

Figure below shows the behavior of the different categories t different wavelengths.

emission wavelength diagram

Metals have various values of emissivity depending on their temperature and the wavelength. Also because of their structure, they tend to reflect the power which results in a low value of emissivity. At low emissivity values, the errors of IR temperature measurement increase. Therefore, the IR controller with the proper temperature range and wavelength must be chosen at which the metal shows the highest possible emissivity.

IR Measurement Optics

IR sensor detects the infrared energy emitted from an object from a circular spot on the object. The circle must be equal or smaller than the object size in order to measure the correct temperature.

Optical resolution of an IR sensor (D:S) is defined by the object distance from the sensor divided by the infrared beam spot size at that distance. Bigger optical resolution means that at a given distance, the sensor can accurately measure smaller objects.

optical resolution sensor

The accuracy of temperature measurements is dependent on the relative infrared beam size and the target dimensions.

Figures below show the D:S charts for the RDO IR sensors for two different lenses.


optic lens: cf2

optic lens: cf4


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