Wavelength Matters

Wedge vs. Direct Pyrometer Measurement for the Continuous Annealing Line

Posted by Jonathan Stronach on Mon, Aug 21, 2017 @ 01:33 PM

 Valid Measurement Conditions for Roller Wedge and Direct View Measurements: 

All infrared technologies produce accurate measures of temperature under ideal conditions.  In the continuous annealing furnace, there are two issues that complicate the temperature measurement process.  The emissivity of the steel strip varies and hot furnace walls create a reflected interference source.  There are two popular measurement techniques applied to the continuous annealing furnace that effectively address these two important application issues.  It is important for any user of infrared thermometers for the continuous annealing process to understand the capabilities and limitations of both of these measurement techniques.

Roller Wedge:

When properly applied, the roller wedge measurement technique eliminates emissivity variation and background reflection errors through the thoughtful installation geometry.  In this case, the pyrometer views a reflected image of the roll rather than a reflected image of the hot furnace wall, and a multi-reflective technique increases the apparent emissivity of the strip to near-blackbody conditions.  This installation technique produces exceptionally accurate temperature values when properly applied and when measurement conditions are valid.  Errors result when the installation geometry is less than ideal and when there is a temperature difference between the strip and the roll.

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Viewing Through Plasma

Posted by Kam Olaogun on Wed, Aug 16, 2017 @ 04:06 PM

States of Matter

There are five states or phases of matter. The three most common states found on earth are solid, liquid and gas. The two less common states of matter occur at opposite ends of the temperature scale. The low-temperature state is the Bose-Einstein state, found only at temperatures very near absolute zero. The high-temperature state is plasma. In the plasma state, there is enough energy stored in the matter for the elemental ions to break free from their molecular bonds. In this state, electromagnetic plasma emissions occur that can interfere with an infrared pyrometer reading.

Common every day examples of plasma emissions include the light from a neon, mercury vapor or metal halide bulb, the glow from a fire, lightning, ion beams and the light from stars including the sun. Plasma is commonly encountered in the industrial arena in vacuum furnaces, when laser energy passes through air or other gas, or any time a gas is heated to a high temperature.

In order to avoid interference from the presence of plasma emissions, an infrared thermometer must use specific narrowband wavelengths. Thoughtful wavelength selection allows Williamson to offer the only ratio (two-color or dual-wavelength) pyrometers able to view clearly through common plasma emissions, and the only short-wavelength pyrometers filtered to avoid many types of plasma emissions

Common Industrial Plasmasplasma nitriding furnace

  • Plasma Vapor Deposition
  • Plasma Ion Nitriding
  • Ion Beam Heating
  • Laser Heating & Welding
  • Blanket Gases for Hot Metal
  • Flames
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Topics: plasma

Interface Module

Posted by Kam Olaogun on Fri, Jul 28, 2017 @ 04:05 PM


IM with Function Keys

The Interface Module (IM) provides a remote human interface with two displays, two analog output signals, two form-C alarms, one TTL alarm, an analog input signal and digital communications capabilities. These human interfaces permit the operator to view measured values, pyrometer settings, and to navigate the setup menu. The IM also includes an AC to DC power supply which provides power to any Williamson Gold or Pro Series pyrometer. The IM is required for connecting a laptop with Williamson ProView software. The two IM displays work as follows:

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Topics: interface module

Single-Wavelength Mode FAQ

Posted by Jonathan Stronach on Thu, Jul 20, 2017 @ 11:38 AM

Ratio and Multi-Wavelength Williamson Pyrometers offer a single-wavelength (SWL) mode of operation.The following notes pertain to commonly asked questions associated with this function. SWL mode can be used to compare readings to single-wavelength models and as a troubleshooting tool.

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Williamson Hot Slug Detector (HSD) for Fiberglass Batting

Posted by Jonathan Stronach on Wed, Jun 28, 2017 @ 10:15 AM

Hot Slug Detector:

Hot slugs form when a process upset causes molten glass to fall from the spinner and into the product during the manufacturing of fiberglass batting. Surrounded by insulating material, these hot slugs remain hot, and days later can cause the paper backing and organic binder material to ignite, creating an expensive and inconvenient fire in a warehouse, on a train or in a truck. The Williamson Model HSD identifies the presence of small slugs below the surface of the fiberglass batting during the manufacturing process. Sensitivity is greatest when mounted after the fluffing blower and before the curing oven. 



The Williamson model HSD combines three innovative Williamson technologies to produce the most viable and reliable hot slug detector.

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Topics: wavelength, pyrometer, application note

How to Ensure Valid Measurement Conditions Using ESP Filtering

Posted by Kam Olaogun on Wed, Jun 21, 2017 @ 10:50 AM

Williamson Two-Color (TC), Dual-Wavelength (DW) and Multi-Wavelength (MW) pyrometers include a series of advanced signal conditioning functions collectively known as ESP Filtering. This advanced signal conditioning feature allows these Williamson pyrometers to recognize valid measurement conditions and to make an active measure of temperature only when these valid measurement conditions exist. This advanced signal conditioning feature is patented by Williamson Corporation and is available only with Williamson pyrometers.


ESP Filtering.png

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Topics: troubleshooting, signal conditioning, valid measurement, ratio, dual wavelength, configure esp, interference, esp filtering, signal dilution, signal strength

Dual-Wavelength Measured Parameters: How each works and when to use it

Posted by Jonathan Stronach on Thu, Jun 15, 2017 @ 01:30 PM

 Williamson Dual-Wavelength Output Descriptions and Functionality:

The Williamson Dual-Wavelength (DW) pyrometer includes a series of output parameters that can be used to confirm the proper operation and accuracy of the sensor. These outputs can be viewed as a display option and can also be configured as an output in the Configure I/O submenu. Measured parameters include filtered temp, unfiltered temp, signal strength, signal dilution, ambient temp, and single-wavelength temp. For each output we can select a parameter, range, and scale. Below we have included more information on each parameter regarding what it does and when it is used.

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Topics: pyrometer

How to Select a Focal Distance

Posted by Kam Olaogun on Thu, May 25, 2017 @ 03:24 PM

When the field-of-view (FOV) is filled by a uniformly-heated target, all Williamson pyrometers are distance-independent (beyond 6 inches for traditional style models) because they are fixed-focus. Pyrometers with an adjustable focus, as offered by others, are accurate only within the focal plane. Adjustable focus in some ways is preferred, but they are also easier to misuse because they are not appropriate for a target that moves significantly and are inaccurate when out of focus. Williamson prefers the fixed-focus approach because it is accurate at all distances.

What is FOV?

FOV/Optics Diagram

The field-of-view (FOV) of a pyrometer determines its area of measurement or spot size in relation to its target. This can be further described as the ratio between the pyrometer’s optical resolution and its focal distance. For example a pyrometer with a focal distance of 40 inches and an optical resolution of 100:1 or D/100 would render a spot size with a 0.4 inch diameter from a 100 inch distance or FOV = 0.4in@40in.

The temperature value measured is unchanged as the distance between the pyrometer and the measured target changes, regardless of the focal distance, as long as the field-of-view is filled by a uniformly-heated target.

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Topics: Field of VIew, Optics, Focal Distance

Application Note: Aluminum Hot Rolling Mill - Coiler

Posted by Thomas Huff on Thu, Apr 27, 2017 @ 08:51 AM

This is part 4 of the 4-part Aluminum Hot Rolling Mill application note series - we hope you enjoyed the complete series! Previous parts can be found in our blog feed.

Application Overview:

The temperature at the coiler is an important process parameter.  If the temperature is too hot, then the metal may soften and stick.  If the temperature is too cool, then the material may become too hard and crack.  Hand-held thermocouple probes are notoriously inaccurate and are prone to misuse and interpretation. 

Williamson Wavelength Advantage:Aluminum Coiler.jpg

The multi-wavelength pyrometer produces a much more repeatable and accurate temperature value than the traditional thermocouple.  The pyrometer can be used to measure the temperature of the strip as it enters the coiler and/or measure the side of the coil while it is being wound or after it has been removed from the coiler.

Pyrometer Benefits:

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Topics: aluminum, hot rolling, application note

Application Note: Aluminum Hot Rolling Mill - Finishing Mill

Posted by Thomas Huff on Wed, Apr 26, 2017 @ 08:51 AM

This is part 3 of the 4-part Aluminum Hot Rolling Mill application note series - be sure to check out the rest of the series!

Application Overview:

Tight control of finishing temperature assures the desired mechanical properties and a blemish-free surface.  The low and highly variable non-greybody emissivity character associated with this aluminum process dictates the use of multi-wavelength infrared pyrometers.

Williamson Wavelength Advantage:Aluminum Finishing Mill.jpg

The traditional multi-wavelength (MW) technology works well at the finishing mill where the process is highly repeatable. While the temperature may vary from alloy to alloy, this variation is repeatable. For exceptional accuracy and repeatability across alloys, the MWx technology is required.

Pyrometer Benefits:

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Topics: aluminum, hot rolling, application note