Infrared Thermometer Calibration

Infrared Thermometer Calibration: Step by Step Guide

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Precise measurements fused with the salient feature of safety, The best Infrared thermometer is the perfect equipment that could flaunt these qualities. Equipped with fast response time and having zero contact capabilities, the infrared thermometer could provide you with the necessary facility of reducing the chance of any accidents, whether those accidents are garbed up as scientific faults or as physical accidents. The infrared thermometer is the perfect antidote for both of them.

As much as the infrared thermometer is easy to use. Its calibration is quite complicated. Its accuracy and uncertainty can increase with a number of factors. Therefore regular calibration of an infrared thermometer is essential.

The complex process of calibrating an infrared thermometer makes it suitable for its owner to leave this job to the pros. Its calibration requires heaps of external influence combined with the use of specialized machinery.

Infrared Thermometer Calibration:

An infrared thermostat works by distinguishing infrared radiation from a specific source and then using the data obtained by a reference to convert it into temperature. These were basically made to calculate the temperature of objects which are not safe to touch.

Infrared Thermometer Calibration

However, all these provisions come with a cost, which is its regular and mildly complex calibration. What are the requisites of IR Calibration? Let’s dive right into it.

Following equipment is a must for calibrating any infrared thermometer:

  • Mounting Device
  • Distance measuring device
  • Transfer Standard
  • Atmosphere temperature thermometer
  • Thermal Radiation Source

Mounting Device:

The mounting device is sort of like a tripod stand for any laboratory work. Sometimes it is used to hold the instrument on which calibration is taking place, and sometimes it is used to hold the devices which perform calibration. However, in the specific case of Infrared Thermometer calibration, it keeps the particular infrared thermometer aligned and maintained according to the S:D Ratio. This device is of vital importance because of the following two reasons:-

It is used to manage the measuring distance

  • It is used to conserve the alignment of the thermometer

For a perfect calibration of an infrared thermometer, the spot to distance ratio (S:D Ration) must be preserved at all costs. The place to distance plays a vital part in the calibration of the Infrared Thermometer.

Distance Measuring Device:

The distance which must be measured for the calibration of an infrared thermometer is the distance of the heat source to the infrared thermometer. For this, a device must be used to accurately measure the gap between the two. Now, no specific method is used to measure this distance. However, a tape measure or a measuring rod is best suitable for measuring the range when calibrating an Infrared Thermometer.

Distance Measuring Device

The distance of the heat source and the infrared thermometer forms one half of the S:D Ratio. The presence of no specific measuring device makes it very important for the calibrator to use the measuring tape with great caution. A slight fault in the measuring distance interferes with the S:D Ratio, which in turn can make the overall calibration flawed.

Transfer Standard:

The transfer standard is used for the calibration of the thermal radiation or the heat source. The transfer standard can be made from the two. It can be a contact thermometer, for example., a thermocouple, a thermistor or any contact thermometer for that instance. It can also be a non-contact thermometer, for example, a radiation thermometer.

The transfer standard can be applied intramural in the laboratory in which the calibration is of the infrared thermometer is taking place, or it can be implemented by using mediator labor external to the lab where the gauging of the Infrared thermometer is being performed.

The first application of the transfer standards is to transfer a measurement parameter from one organization to the other. It is used to transfer settings from a  chief standard to the secondary standard, or it can also be used to shift it from the secondary standard to some other working standards

Atmosphere Temperature Thermometer:

The atmosphere temperature thermometer or the ambient temperature thermometer is used to detect the temperature present inside the laboratory. This is a vital instrument for the calibration of an infrared thermometer as an external influence especially the influence of temperature on a thermostat can play a significant role in increasing the uncertainty.

The accuracy of the ambient temperature thermometer itself plays a very pivotal role in the perfect calibration of an infrared thermometer. Therefore, it is imperative that for the calibration of the infrared thermometer that the instruments that are being used for the calibration are also quite precise and accurate.

Thermal Radiation Source:

The biggest concern while choosing a radiation source is determining the size of how big the source should be. This is imperative because of the infrared thermometer field of view.

A source size of almost about 5 inches(125 millimeters) is required for Fluke Calibration. Thermal Radiation sources for other manufacturers can be derived from experimentation.

This device is used to provide the heat which is used for the calibration of the infrared thermometer. Due to this, it must be itself be calibrated to a perfect set of standards.

Laboratory Setup:

To perform the infrared thermometer calibrations minimum errors, a proper laboratory setup is essential. The temperature which is set up in the laboratory should be maintained within limits. The atmospheric temperature while calibrating the Infrared thermometer should be managed according to the restrictions identified for the Infrared thermometer during its calibration.

The maintenance of the atmospheric pressure inside the laboratory during the calibration of the Infrared thermometer is essential because of two reasons. Firstly, it is necessary for the perfect calibration of the Infrared Thermometer as the uncertainty error of the Infrared thermometer is greatly affected by the external influence of temperature.

Secondly, the temperature limits on which this thermometer was calibrated in gives the consumer the information denoting temperature in which it was scaled.

How you position the equipment when you are calibrating an Infrared thermometer plays a significant role in the degree of calibration. The importance of the location of materials is mainly governed by the presence of Reflected Temperature and especially when calibrations are being at a low temperature.

To correctly set up the laboratory equipment, the following changes should be made:

  • You should never set up the pieces of equipment in a way that the heat source begins to face the radiation source,
  • You have to keep on checking the temperature of the walls. This is because the temperature of the barriers facing the radiation source should be that of the laboratory. This becomes a matter of prime importance when the wall meets the exterior wall or an exterior window,
  • The position of the person performing the calibration should be considered since his or her position dramatically affects the temperature that is reflected.


1. Preparation:

Before the calibration of the Infrared Thermometer, certain specifics must be taken care of. These are listed as the following:-

  • The infrared thermometer must be given some amount of time so that it can reach the temperature of the laboratory. It approximately takes about 15 minutes to preserve this state. This is undoubtedly a significant step especially when a thermometer is brought from the outside
  • The cleansing of the lens, which most of the calibrators do, is not recommended by professionals. If a glass should be cleansed, then it should be washed with either the permission of the customer or according to the guidelines provided by the manufacturers manual.
  • The radiation source should always be set up, as mentioned above, to the desired temperature limits. If the calibration is to be maintained with dry gas, then the purge should always be set up before the radiation source is stabilized.

2. The Procedure:

The steps which are to be mentioned below should be replicated several times for each point.   They are as following:-

  • If our IR has the heat setting of reflected sources, then it should be made according to the heat source temperature. The setting of the heat source is also sometimes called background temperature. However, it must be noted that Fluke IR’s do not have reflected temperature settings. The sources calibrated emissivity should always be the same as the emissivity setting of the infrared thermometer. When the Infrared thermometers have fixed emissivity, then specific, measurable changes should be made.
  • The next important step is always to align the Infrared Thermometers. To align the infrared thermometer, we must first set the measuring distance. Measuring distance, as mentioned above, is the distance between the radiation source to the infrared thermometer. Once the length is set, the thermometer needs to be centered on a calibrator surface.
  • The infrared thermometer could be centered on the calibration surface by maximizing the signal or by moving the thermometer up and down and also shaking it from side to side.
  • After aligning the thermometer, the line which passes through the calibrator surface should not be more than five degrees from the perpendicular.
  • At this point, measurement is ready to be made. Although this process sounds quite complicated in reality and also in performance, it actually is quite simple. It takes almost fifteen seconds to measure each calibration point.


The user of the infrared thermometer should tell the technician which calibration point he or she wants to use. All the calibration points should be based on the needs and wants of the customer. If he or she does not know what the calibration point is, he should seek advice from the technician.

If an infrared thermometer is being used in a low range of temperature, then, in that case, the one calibration point is enough. However, if the IR’s are being used in temperatures which are having a broad range, then, in that case, three calibration points must be availed.

This must at least represent the least, the highest, and the moderate scope of the infrared thermometers range that could be availed. The sequence of the points could, in some cases, be random. However, it is always advised due to the presence of the lower upset to perform, the weak calibration points first, and the higher points at last.


The report that you will give to the owner of the IR must be in a proper and a well-developed form and should meet all the demands of the respected body of the laboratory. The result of this scaling must be noted. The best way to present this information is to make a grid of different sources of temperature versus the IR. An indication of whether the inference is passed or failed may also be added to the table. These reports should include the following

The results of the calibration should be presented. This is ideally represented by table temperatures obtained from the source versus IR values that are experimentally derived. An indication of whether the inference is approved or rejected may also be portrayed in the grid that we have just made. The report must have the following:-

  • Date of calibration
  • Measuring distance
  • Emissivity setting of the infrared thermometer
  • The diameter of the source
  • Ambient temperature


The instruments that are used in the laboratory are used so frequently that it becomes easy for a person to not take care of the need of the devices themselves. In every experiment, analytical data is crucial. A fault of even milli-degrees can somehow reverse the whole equation. Therefore, we must be cautious when we are calibrating an instrument.

This is because the device which is being used is only as precise as the pieces of equipment which are being used. If the equipment which was used for the calibration of the instrument were no accurate and precise, the device itself would not be specific.

An infrared thermometer is such an instrument that requires several more equipment for its calibration. Therefore it is best to leave its calibration to the professionals. Although we can calibrate an infrared thermometer ourselves, with just a bit of knowledge and technique.

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