RayTek ThermoView Ti30 user manual How to assure accurate temperature measurement?, Emissivity

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Q. How to assure accurate temperature measurement?

A. A solid understanding of infrared technology and its principles lies behind accurate temperature measurement. When the temperature is measured by a non- contact device the IR energy emitted from the measured object passes through the optical system of the thermometer or thermal imager and is converted to an electrical signal at the detector. This signal is then displayed as a temperature reading and/ or thermal image. There are several important factors that determine accurate measurement. The most important factors are emissivity, distance to spot ratio, and field- of-view.

Emissivity

All objects reflect, transmit and emit energy. Only the emitted energy indicates the temperature of the object. When IR thermometers or thermal imagers measure the surface temperature they sense all three kinds of energy, therefore all thermometers have to be adjusted to read emitted energy only. Measuring errors are often caused by IR energy being reflected by light sources.

Some IR thermometers and thermal imagers allow you to change the emissivity in the unit. The value of emissivity for various materials can be looked up in published emissivity tables.

Other units have a fixed, pre-set emissivity of 0.95, which is the emissivity value for most organic materials and painted or oxidized surfaces. If you are using a thermometer or thermal imager with a fixed emissivity to measure the surface

July 1, 2003

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Contents ThermoView Ti30 User’s ManualContents Qualitative and Quantitative Temperature Measurements Appendix B Infrared Theory Q&A Glossary Warranty Information Customer Service Contact Information Introduction Quick Specifications Table NetdUnpacking Your New Imager Removing the Battery Pack First, the BatteriesBattery Packs Charging the Rechargeable Battery Pack Normal Charge CycleDocking Station LED Indicators Getting Started Attaching the Wrist StrapTurning the Unit On Displaying ImagesInformation Screen Normal Mode Settings and Controls KeypadThermoView Imager Settings Switches icons not shown ThermoView Imager Settings Switches Laser On/Off Toggle ButtonJapanese Laser Aperture and Optical ChannelLCD Backlight Illumination Switch Palette SwitchMeasurement Mode Switch Centigrade/Fahrenheit Toggle ButtonGain and Level Thumbwheels Focus WheelAutomatic Semi Automatic Level pointTrigger Location of the Focus WheelMan Machine Interface Flow Charts Main LoopImage Recording Procedure Emissivity Adjustment Procedure July 1 Version Quick Image Fix Procedure Array Recalibration Procedure Recording an ImageRetrieve Mode Retrieving an ImageInstalling the Software Downloading and Looking at ImagesConnecting the Docking Station to Your Computer Hooking Up the Docking StationConnecting the USB Connector to the USB Port InsideIR Main Screen at Program Launch Downloading Images Sync buttonSaving Images Download Data ScreenSetting the Imager Clock Contents of Images FolderJuly 1 Version Field USB Port Looking at Your Downloaded ImagesViewing Thumbnail Images Viewing a Single Image Importance of Focusing Obtaining the Best ImageSelecting the Measurement Mode Selecting the Color PaletteLevelGain Min Level  Gain Max Level  Gain Tip Qualitative and Quantitative Temperature Measurements Distance to Target Spot RatioOptical Diagram Field-of-ViewDS ratio D / S = Ambient Temperatures Environmental ConditionsReflected Temperature Compensation EmissivityReflected Temperature Compensation Organizing Your Data File ManagementUploading Data to the Imager Uploading Data to Your ThermoView Ti30 ImagerEditing Data Before Upload RTC OFF Analyzing Your Data Single Image ScreenScale Limits Sample Image at Original Scale Limits Sample Image at Original Isotherm Setting IsothermsTemperature Table Tab Additional Image Analysis ToolsTemperature Table Profile TabHistogram Tab Profile TabMenu Bar New FolderThermoView Imager Info ExitFahrenheit CelsiusExport Temperature Table Export ImageCreate Report HistogramCopy Profile Chart ContentsCascade Tile HorizontalReporting Your Findings Thermographic ReportImager Accuracy Chart Appendix a Technical ReferenceImager Reading Error vs Source DS Typical Emissivity ValuesAluminum Unoxidized Ni-Cu Gob Why use noncontact infrared thermometers? Appendix B Infrared Theory Q&AHow does IR work? How to assure accurate temperature measurement? EmissivityDistance to spot ratio Field-of-viewHow to take temperature measurement? What are the most popular applications?Glossary Background Temperature BlackbodyCalibration Calibration SourceDisplay Resolution DriftEMI/RFI Noise Far FieldFocus Point or Distance Full ScaleFull Scale Accuracy Gray BodyLaser LoopMicron or µm Minimum spot sizeOptical Resolution Non-Gray BodyOptical Pyrometer Pyroelectric DetectorReflected Temperature Compensation ResolutionRelative Humidity RepeatabilityStorage Temperature Range TemperatureTemperature Coefficient or Ambient Derating Spectral ResponseTemperature Resolution Thermal ShockTime Constant Transfer Standard