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How to Get the Accurate Reading

1. Adjust the Emissivity

If the emissivity setting of the thermometer is adjustable, please adjust the Emissivity to be complied with the Blackbody target.

2. Determine The Measuring Distance

Measuring distance is determined on the Aperture Diameter of Blackbody and the D/S ratio of the thermometer. Check the Aperture Diameterof the Blackbody, than follow below recommendation table to measure temperature at suitable distance.

Aperture Diameter of Blackbody (A) Measuring Distance TN1( 1:1 ) Measuring Distance TN408LC( 11:1 ) Measure Distance
TN40ALC( 20:1 )
65 mm
(ex:ISOTECH R700)
25mm 120 mm 220mm
60 mm 25 mm 100 mm 170mm
56 mm
20 mm 80 mm 130mm
50 mm 20 mm 40 mm 80mm
35 mm As close as possible As close as possible As close aspossible

  • Table of measuring distance for various Blackbody

3. Evaluation Principle

Normally, the measuring distance is determined by below principle;

Aperture Diameter of Blackbody = Nominal Spot Size At That Distance × 2

Description of Symbols

(1).A = S × 2

(2).A means the "Aperture Diameter of Blackbody"

(3).S means the "Nominal Spot Size at Distance D"

(4).D means the "Measuring Distance" between TN and Blackbody

4. Lens Cleaning before Measurement

Blow off loose particles using clean compressed air.

Carefully wipe the surface with a moist cotton swab.

5. Note for Low Temperature Blackbody

While using the low temperature blackbody at room environment, the surface of the blackbody is very easy to get frost that will change the surface emissivity of the blackbody.

Keep the blackbody aperture closed while no measurement is proceeding to avoid this problem.

6. Thermal Shock

Avoid abrupt changes in environment temperature. If this occurs, allow 20~40 minutes for thermal stabilization before use to prevent the possibility of inaccurate temperature readings.

7. The effect of different Emissivity setting between target and Thermometer

Most of the thermometers of ZyTemp have a default emissivity setting of 0.95.
The surface emissivity of a material is measured by the amount of energy emitted when the surface is directly observed.
Please refer to http://www.zytemp.com/infaredl/emissivity.asp for the detail emissivity table of metal and non-metal materials.
When the emissivity setting of the thermometer and target surface are different, please adjust the emissivity setting of the thermometer to the proper value as the same as the target. If the emissivity of the thermometer is fixed at some value( such as 0.95 ) and can't be changed, please consult with ZyTemp for how to judge the reading accuracy of the thermometer.
The calculation is based on Stephen-Boltzmann's law:


Where: ???? E=infrared radiation energy
Tobj= target surface temperature in Kelvin

Tamb=ambient temperature in Kelvin

8. How to evaluate the emissivity of a target surface?

One can discover the emissivity of an object with two thermometers or one dual functions thermometer such as TN4xxLC or TCT series from ZyTemp. Simple use the contact surface type probe to touch that object to get the (contact) temperature, then use the non-contact sensor(infrared) to obtain that surface temperature. Later, adjust the emissivity until the infrared thermometer displays the same temperature as the contact type thermometer. Now you know the correct emissivity of the object.

9. What's the minimum spot size can be measured by an IRT?

It depends on the optical aperture size. For example, the minimum spot size TN4 can take will be not smaller than 25mm as its optical opening. And user can only get this spot at a very close distance.(<=2.54cm).

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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