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IR thermometer operation is based on the physical principle that all bodies having a temperature greater than absolute zero (0 K, –273.16°C, –459.69°F) radiate energy. The heat in such bodies causes molecular vibrations that induce electron vibrations. These electron vibrations in turn provide the electromagnetic coupling to produce emission. The wavelengths of the emitted radiation are temperature dependent, which means that the wavelength is associated with temperature; the amplitude is also influenced by a surface characteristic--emissivity--of the radiating body. Emissivity is the ratio of the energy radiated by an object at a given temperature to that emitted by a perfect radiator (blackbody) at the same temperature.”
All matter--animate or inanimate, liquid, solid, or gas--constantly exchanges thermal energy in the form of electromagnetic radiation with its surroundings. If there is a temperature difference between the object in question and its surroundings, there will be a net energy transfer in the form of heat; a colder object will be warmed at the expense of its surroundings, a warmer object cooled. And if the object in question is at the same temperature as its surrounding, the net radiation energy exchange will be zero.” “In either case, the characteristic spectrum of the radiation depends on the object and its surroundings' absolute temperatures. Non-contact temperature measurement, involves taking advantage of this radiation dependence on temperature to measure the temperature of objects and masses without the need for direct contact.”
While there are many different shapes and styles of handheld infrared thermometers, and many features available, the basic function is very similar in very nearly every variation. The first step in taking a measurement, is determining the desired target. All portable infrared thermometers regardless of design will have a means of "aiming" the instrument at the target. Some versions simply are shaped in such a way that pointing at the target is the targeting method. Others have a guide such as a laser spot, or group of laser spots that indicate the area being targeted. The temperature measurement is taken when the "trigger" is activated. This is usually a button located either underneath the pyrometer (gun style), or on top (television remote control style). The accuracy of the measurement depends on several factors. See What is the distance to spot ratio? to understand the elements governing accuracy.
D/S Ratio- Distance to Spot ratio refers to a very important feature of your infrared thermometer. This ratio is the size of the area being evaluated by the infrared thermometer as it relates to distance. In other words, the area being measured becomes larger as the distance increases. This has a profound impact on the accuracy or precision of the reading. If the target you are measuring is 6 inches in size, and your infrared thermometer has a D/S ratio of 8:1, than the maximum distance you can reliably measure the temperature of the target is 48 inches. Beyond this distance, not only is the target being measured, but whatever else falls within the "spot" is being measured as well. This means that if a very hot object is the target, and it is in cooler surroundings, than measurements taken beyond the maximum distance will include cooler elements, and lowering the "average" of what is in the "spot".
D/S Ratio X Target Size, or 8:1 X 6 = maximum measure distance of 48 inches.
As the target size decreases, or the distance to the target increases, a larger D/S Ratio becomes necessary. Using the same example above, and changing first the target size, and then the D/S ratio, you can see that this formula helps you decide the correct D/S ratio and therefore the Infrared Thermometer for your needs.
D/S Ratio X Target Size, or 8:1 X 2 = maximum measure distance of 16 inches.
D/S Ratio X Target Size, or 12:1 X 2 = maximum measure distance of 24 inches.
D/S Ratios vary greatly, so carefully compare this feature of IR Thermometers when comparison shopping. This ratio, and temperature range are the two biggest factors to consider when shopping for an Infrared Thermometer!
While infrared thermometers are primarily used in industry, there as several useful applications for around the home!
Heating and cooling efficiency - This is a popular use for those who live in extreme climate areas. Very cold winters, or very hot summers mean that escaping heating or cooling drives up the electric bill!. During the extreme weather time of the year, the user can locate escaping heat, or cold around windows and doors and dramatically improve the heating, or cooling efficiency of their home! Even a reasonably small area around a window or two that you can seal, may well return your investment in your thermometer in a single season by reducing heating or cooling costs!
Electrical Troubleshooting - A troublesome circuit breaker "popping" frequently, can be an indication of loose connections within the electrical box. The qualified do-it-yourselfer can easily locate a loose connection by "scanning" through the electrical box. Overall, the contents of the box should be within a temperature "range", but any loose connections will be drawing additional amperage and causing extra heating as a result. Of course, as always when dealing with electricity, only qualified persons should make corrections, and only after taking the necessary precautions.
There are literally hundreds of applications in industry for infrared thermometers. Some uses would not occur to the average person. Here is a list of some common applications, and a few unusual ones as well!
HVAC Heating Ventilation and Air Conditioning Technicians are one of the most frequent users of portable infrared thermometers. It is vital in their job, to take accurate measurements, usually from a distance to gauge the efficiency of the unit by measuring the degree of cooling (or heating) of the air
Home Inspections- Home inspectors have many uses as listed in the categories above. They also might use their infrared thermometer to measure hot water temperature, look for insulation leaks etc. This is becoming on of the most popular applications for pyrometers.
Health Inspectors- Perhaps not an example that would occur to everyone, health inspectors closely monitor many temperature related things in and around food handling and preparation. Heating bins and surfaces hot enough? Refrigerators and freezers cold enough to protect food from spoiling? Restaurant owners, does your health inspector use an infrared thermometer? If so, getting the same tool he uses is wise to avoid surprises!
Process Controls- This is a very broad category, but the following list details some industries that utilize handheld infrared thermometers for monitoring and maintaining temperature sensitive aspects of their business. Some examples are:
- Measuring the surface temperature of curing concrete to determine if cracking is a danger.
- Measuring asphalt prior to pour to ensure smooth application.
- Measuring ink temperatures prior to mix for accurate color matching in printing presses.
- Monitoring the temperature of lamination materials for proper adhesion.
- Verifying part temperature following an oven baking operation to ensure proper drying, ductility, curing of paints and coatings etc.
- Any application where taking temperature is either impossible through direct contact because of barriers or distance.
- Taking temperatures in a hazardous environment where the user can maintain a safe distance by using non contact infrared thermometer technology.
There are many factors to consider when shopping for an infrared thermometer. There are many features and variables available, and of course, a very, very wide range of prices. The following list of factors is structured so that the factors at the top of the list will likely have the greatest impact on cost. You will notice that some of these factors are related in the way that they affect the value of the instrument. So ask your self the following questions before shopping, and use the list below to help guide you in selecting the best infrared thermometer for your needs. You can than start comparison shopping with an arsenal of information that will enable you to get the best value! The one factor not listed below is Warranty from the provider. While shopping, use this to determine what distributor has the greatest confidence in the product they are selling!
Question: What is the minimum and maximum temperature I might expect to be measuring?
Question: What is the maximum distance I may be measuring from?
Question: What is the smallest target object I may need to measure?
Question: How accurate do my results need to be?
Question: Do I need features like, Overtemp. alarm, Logging multiple readings etc.
Question: Do I need a targeting guide like a laser spot for accuracy?
Temperature Range - One of the most important feature that affects the cost of an infrared thermometer is the temperature range of the instrument. A couple of important things to note, is that most thermometers fall into several groups that have a natural separation of costs. Medical Use, Smaller Range, Medium Range, Lower Minimum Medium Range, Wide Range, Very Wide Range.
Obviously an infrared thermometer intended for medical purposes only needs a limited range. There is a much greater need for accuracy however. These are often very inexpensive and intended only for this purpose. A more expensive unit could take measurements in the appropriate range, but the accuracy would likely not qualify, eliminating it as useful for this purpose. Of course, plus or minus 2 degrees F is the difference between normal, and a fever!
Smaller Range infrared thermometers vary somewhat, but generally have a total range of 450 F or so. A typical range for an instrument in this category might be -4F to 425 F. Somewhat lower and higher variations will be noted, but this is an average for this category. Usually inexpensive, and useful for many applications, this group is your choice if this range meets your needs.
Medium Range infrared thermometers typically are more consistent in their grouping regarding min. and max. temperature. The average temperature range for this group is -25F to 999F. This is the group that has the most versatility without adding a great deal of cost in most cases.
Lower Minimum Medium Range infrared thermometers are also sometimes called "Food Service IR Thermometers". This is the case because the lower end of the range reaches down below -40F. (Usually -50F or more) This is important to the food service industry to ensure the safety and freshness of frozen foodstuffs. This is the group most likely used by health inspectors.
Wide Range IR thermometers represent the first big jump in cost. For this reason, the health inspector for example, will likely select the prior category. Number one because of cost, and number two, because he would likely not need the extreme upper range that this unit offers. Although the lower end is the same as the previous group, and the accuracy is the same, the extra cost may not be attractive to that consumer, unless the thermometer will be used in other environments requiring the expanded upper range. Typical ranges for this group go below -50F to 1000+ F.
Very Wide Range infrared thermometers are obviously the most costly group of IR thermometers, if we ignore other features than range alone. Typical temperature ranges for this group can be nearly -60F to 1800+ F! Found mostly in high end industrial applications, these units are rarely found in everyday uses as mentioned above. They are reserved for special applications and as such are priced accordingly!
Conclusion: The better value will be the instrument with the greatest range for the same cost, all other factors being equal.
Distance from the target / target size - These go hand in hand as we look at the Distance to Spot Ratio. This feature is as important as temperature range when accurate readings are needed. See what is the distance to spot ratio. This determines many things among which are, the smallest target you can measure and from what distance. Distance to Spot Ratios (D/S) will vary dramatically, and have an equally dramatic impact on cost. D/S can be as low as 4:1 and as high as 50:1 or more!
Conclusion: The better value will be the instrument with the highest D/S ratio for the same cost, all other factors being equal.
Instrument Accuracy - Accuracy seems to be, on the surface a simple factor. However, if cost is a concern as it generally is, than selecting an infrared thermometer that meets your needs as opposed to exceeding your needs, may mean a reduced cost for a suitable instrument. I always suggest erring on the side of caution, and making sure the accuracy is adequate and then some.
Conclusion: The better value will be the instrument with the greatest accuracy for the same cost, all other factors being equal.
Features - The importance of various features is completely dictated by the intended end use. If simple measurements are all that is required, than data logging, averaging, and high temperature alarms etc. are not necessary. In many cases however, these features may be available for a minor added cost when selecting an upgraded unit, or even the same cost from another brand name! This is where the diligent shopper can ensure that the best infrared thermometer for his or her needs is acquired by visiting several outlets and comparison shopping.
Conclusion: If extra features are needed, the instrument with the best features for the same cost, all other factors being equal will be the greatest value, and most useful.
Laser spots / Targeting Guides - The need for targeting aids such as laser spots or sighting scopes is primarily dictated by the need for accuracy. It is important to note, that recent versions of infrared thermometers available now, almost always have the laser option. The one negative to this feature is that it is a drain on the battery. Many versions have a laser on/off feature, which can be disabled to either achieve extended overall battery life, or preserve remaining life when the battery has been in service for a while and is becoming drained.
Martrow Technical Products Return Policy
1 - Our products and services must meet or exceed your expectations based on our promotional information available throughout this site.
2 - If you are not satisfied with your purchase as stated above, you can return your item within 30 days for a full refund of the purchase price.
3 - The item must be returned with the original packaging, undamaged, and with the contents of that package intact.
4 - Shipping costs are excluded from this return policy.
5 - Contact our Toll Free number for instructions for product returns.
Portable Hardness Testers
All Leeb or rebound type hardness testers function on a simple principle. As the term rebound suggests, by using a spring loaded impactor to rebound off of the test surface a velocity before and after impact is taken. These velocities are measured when a coil on the impactor creates a small voltage as it passes through the guide tube first before impact, and just after. By comparing these two velocities, a measurement proportional to hardness can be created as softer material absorbs more energy, thus reducing the second velocity following rebound.
While there are many different makes and models of portable hardness testers, and many features available, the basic function is very similar in very nearly every variation. The first step in taking a measurement, is determining the desired target. All portable hardness testers regardless of design will have a means of supporting the the instrument against the surface to be tested. The shape of the surface to be measured determines several things. For example a different attachment is used for round material versus flat. A load is placed onto the spring by "charging" the instrument. Most designs incorporate a cocking motion that prepares the impactor to be released when the "trigger" is activated. The energy stored in the spring launches the impactor towards the surface to be measured and a reading is taken. It is important to remember that to obtain accurate readings, the impactor must strike the surface at as near perpendicular as possible. Also, surface finish can impact the accuracy of the reading, or perhaps even the ability to take a reading whatsoever. Some units offer an interchangeable set of optional impactors that can be used for a variety of surfaces and hardness ranges.
The Leeb Hardness scale indicates material hardness expressed in terms of a specific ratio of velocities taken from the rebounding impactor. Leeb value can range from 0 to 1000. This value represents the difference between the first and second velocities as described previously. With a difference of zero, the hardness can be expressed as top of scale, or 1000, and the reverse is true of the greatest difference representing the softest possible reading. Most instruments make a ready calculation based on some operator input that converts the Leeb value to the hardness scale desired for the test results. Conversions to popular hardness scales such as Brinell, Rockwell A,B and C and other industry standard hardness scales are standard features on most units.
One of the most attractive elements of the portable hardness family of testers is their utility in field applications where standard hardness measurements are either not possible, or impractical. Some common field applications would include the mining industry where stress components can be tested without disassembly. Aerospace inspections on aircraft components avoiding very costly breakdown of airframe and power plant assemblies by performing testing in close quarters. Receiving inspection of raw material is made possible without even unloading or breaking down bulk deliveries with the portability of Leeb type testers
There are literally hundreds of applications in industry for portable hardness testers. Process monitoring is made possible anywhere in the facility. Ease of use and rapid results make this a practical and accurate method to check in house heat treating effectiveness in real time. Machining processes that are subject to work hardening, or particular hardness is required prior to or during processing can readily be confirmed. The Q.C. lab, and receiving inspection are two other primary areas where this type of instrumentation is commonly found.
There are many factors to consider when shopping for a portable hardness tester. There are optional features and configurations available, and of course, a wide range of prices. You will notice that some of these factors are related in the way that they affect the value of the instrument. So ask yourself the following questions before shopping, and use the list below to help guide you in selecting the best portable hardness tester for your needs. You can than start comparison shopping with an arsenal of information that will enable you to get the best value! The one factor not listed below is Warranty from the provider. While shopping, use this to determine what distributor has the greatest confidence in the product they are selling!
Question: What is the material type and overall mass I might expect to be measuring?
Question: What is the minimum thickness of material I may be measuring?
Question: How accurate do my results need to be?
Question: Do I need features like, data output, data logging, multiple readings with math functions etc.
Material type and Mass -
Material shape, thickness, overall mass and type are very important considerations when shopping for portable hardness testers. When shopping for your hardness tester it is very important to give a full description of your current, and even future applications so the potential provider can ensure that everything you need can be obtained to ensure a successful acquisition.
Be sure to address the following topics-
Hardness scale results are desired in.
Maximum surface roughness to be encountered. Specialty impactors may be required for certain conditions. In some cases very rough surfaces may not be suitable for this technology.
Shapes / Forms to be inspected material will determine the optional shape adapters that may be necessary to fulfill your requirements.
Material thickness is important due to the fact that minimum inspectable thicknesses depend on the alloy to be evaluated. Make sure that your application falls within this range when making inquiries. Optional impactors can also assist in this category, so be specific in regard to this topic.
Instrument accuracy is a measurable means of comparing quality and best value for the cost. Some specifications are expressed in terms of percentage, and others in scale value.
Features offered vary greatly. Typically as features are added, and options selected the amount of the investment should be expected to increase accordingly. Selecting features and options needed, and ignoring those that fall outside of the application needs will help in controlling the size of the investment required.
Conclusion: The better value will be the instrument with the greatest accuracy and included features, all other factors being equal.