Handheld temperature measurement devices

Temperature measurements are fundamentally important to many industrial processes. Many measurements are made with a probe in or on a pipe or vessel. However, if an object cannot be contacted, measuring temperature may be difficult. Contact sensors such as thermometers, thermocouples, and RTD's are accurate and cost effective but not always practical.


  • Types

  • Applications

Contact devices
Noncontact Devices

Temperature measurements are fundamentally important to many industrial processes. Many measurements are made with a probe in or on a pipe or vessel. However, if an object cannot be contacted, measuring temperature may be difficult. Contact sensors such as thermometers, thermocouples, and RTD's are accurate and cost effective but not always practical. For many industrial applications, optical and infrared temperature sensors can carry out measurements virtually impossible for contact sensors.

Contact devices

There are several popular methods for measuring temperature by contact. Readings are produced by the expansion of a liquid or metal, the generation of a current in the presence of heat, or the generation of resistance to current flow in the presence of heat. The first two are called active devices; they generate a signal. The third is called a passive device; it creates a blockage. All these devices react proportionally to the temperature they contact.

Liquid-in-glass thermometers

Liquid-in-glass thermometers consist of a glass envelope, a responsive liquid, and an indicating scale. They were invented about 300 yr ago and are still the most commonly used temperature-indicating devices.

Some advantages of these thermometers are:

  • Low cost

  • Simple to use

  • Ease of checking for damage

  • No power requirement.

    • Bimetal thermometers

      Bimetal thermometers use a composite material made up of strips of two or more metals joined together that have different expansion rates. The strip tends to change its curvature when subjected to a change in temperature.

      These devices will retain their accuracy indefinitely. Accuracy is within 1% of scale range at any point on the scale. They can be used beyond their range by 100% below 250 F, 50% up to 500 F, and 10% up to 750 F without damage.


      When dissimilar metal wires are joined and the joint is heated, a voltage is produced that is proportional to the temperature. Various combinations of metal wires respond differently to temperatures.

      The selection of thermocouple wire depends on a variety of factors including:

      • Temperature to be measured

      • Compatibility with the ambient atmosphere

      • Cost

      • Millivolt output

      • Linearity.

        • RTDs

          Resistance temperature detectors (RTDs) are based on the change of electrical conductivity with temperature. They consist of an encapsulated coil of wire (the sensing element), internal lead wires, supporting and insulating material, and a protective case. Platinum wire has the optimum characteristics for service over a wide temperature range.

          Noncontact Devices

          When temperatures are extremely high or the object to be measured is remotely located, noncontact devices must be used. These devices use the radiant energy from the hot source to determine its temperature.

          Optical pyrometers

          Optical pyrometers measure the intensity of the radiant flux emitted in a narrow wavelength interval in the visible spectrum. The temperature of the target is determined from its spectral radiant intensity. Temperatures from 1400 to 5200 F can be measured. With special absorbing screens, this can be extended to 10,000 F.

          Infrared sensors

          Infrared sensors collect radiation from a target. The infrared energy is isolated and measured using photosensitive detectors. The detectors convert the infrared energy to an electrical signal, which is then converted into a temperature value. For accurate temperature readings, the target should be larger than the instrument's field of view. This device can measure temperatures from -32 to 5000 F.

          Temperature sensors


          Liquid-in-glass Thermometers

          LiquidTemperature range, F
          Mercury-38 to +1110
          Mercury alloys-76 to +250
          Organic alloys-328 to +450

          Thermocouple comparison

          ISA TypePositive wireNegative wireRecommended temperature, FAcceptable ambient conditions
          TCopperConstantan-450 to +750Oxidizing reducing
          JIronConstantan0 to +1650Reducing
          KChromelAlumel0 to +2300Oxidizing or neutral
          EChromelConstantan-300 to +1600Oxidizing
          R,SPlatinum-rhodiumPlatinum0 to +2800Oxidizing
          BPlatinum 70-Rh30Platinum 94-Rh60 to +3200Inert or slow oxidizing

The Top Plant program honors outstanding manufacturing facilities in North America. View the 2017 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
SCCR, 2018 Maintenance study, and VFDs in a washdown environment.
Welding ergonomics, 2017 Salary Survey, and surge protection
2017 Top Plant winner, Best practices, Plant Engineering at 70, Top 10 stories of 2017
Product of the Year winners, Pattern recognition, Engineering analytics, Revitalize older pump installations
Control room technology innovation; Practical approaches to corrosion protection; Pipeline regulator revises quality programs
The cloud, mobility, and remote operations; SCADA and contextual mobility; Custom UPS empowering a secure pipeline
Setting internal automation standards
Knowing how and when to use parallel generators
PID controllers, Solar-powered SCADA, Using 80 GHz radar sensors

Annual Salary Survey

Before the calendar turned, 2016 already had the makings of a pivotal year for manufacturing, and for the world.

There were the big events for the year, including the United States as Partner Country at Hannover Messe in April and the 2016 International Manufacturing Technology Show in Chicago in September. There's also the matter of the U.S. presidential elections in November, which promise to shape policy in manufacturing for years to come.

But the year started with global economic turmoil, as a slowdown in Chinese manufacturing triggered a worldwide stock hiccup that sent values plummeting. The continued plunge in world oil prices has resulted in a slowdown in exploration and, by extension, the manufacture of exploration equipment.

Read more: 2015 Salary Survey

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
The maintenance journey has been a long, slow trek for most manufacturers and has gone from preventive maintenance to predictive maintenance.
This digital report explains how plant engineers and subject matter experts (SME) need support for time series data and its many challenges.
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.
Maintenance Manager; California Oils Corp.
Associate, Electrical Engineering; Wood Harbinger
Control Systems Engineer; Robert Bosch Corp.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
click me