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iTHERM SurfaceLine TM691
New

Metric/imperial TC tube skin thermometer for harsh environments such as fired heaters, reformers, heat exchangers, boilers

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Have questions about this product?

iTHERM SurfaceLine TM691
New

Metric/imperial TC tube skin thermometer for harsh environments such as fired heaters, reformers, heat exchangers, boilers

Get a quote
Office situation support
Have questions about this product?

Benefits

  • Increased plant and process safety: early detection of overheating and critical operating conditions of process pipes
  • Improved energy efficiency: Assessing and optimizing burner operation and heat distribution
  • Improved product quality: stabilized process conditions due to accurate temperature measurement
  • iTEMP temperature transmitter with all standard communication protocols and optional Bluetooth® connectivity
FLEXible answers to individual needs
Current product

iTHERM SurfaceLine TM691

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  • Specialized products
  • Designed for demanding applications

What is FLEX?

FLEX selections
Technical excellence
Simplicity
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Fundamental selection Meet your basic measurement needs
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Lean selection Handle your core processes easily
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Extended selection Optimize your processes with innovative technologies
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Xpert selection Master your most challenging applications
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Manufacturer's warranty

Engineered for confidence

Our instruments are designed for long‑lasting performance, precise measurement, and dependable operation in demanding industrial environments. Each product includes a standard manufacturer’s warranty that reflects our commitment to quality and to the trust you place in our solutions.

Should a warranty case occur, the device will be assessed and the applicable remedy will be provided in line with the warranty terms – helping ensure a reliable and efficient resolution and supporting continued operation of your measurement point.

Request for extended warranty

If you require extended warranty coverage, simply contact your local Endress+Hauser representative. Our experts will advise you on the available options to match your application and risk profile, helping you protect your investment, reduce unexpected repair costs, and ensure reliable long‑term operation beyond the manufacturer's warranty period.

Learn more

Warranty terms apply

The manufacturer's warranty and extended warranty are subject to specific conditions. For full details, please refer to the locally applicable General Terms and Conditions (GTC), which can be found on the respective country page of our website.

Services by your side

Right‑first‑time commissioning, worldwide

Endress+Hauser’s qualified service engineers ensure your measurement devices are commissioned right the first time, delivering application‑aligned accuracy, regulatory compliance, and operational confidence from startup onwards, anywhere in the world.

Remote support you can trust wherever you operate

With Endress+Hauser Smart Support, you benefit from faster issue resolution, higher uptime, reliable global expertise across the entire product lifecycle – and lasting peace of mind.

Committed to long‑term, sustainable performance

With deep field expertise, harmonized processes, and continuous monitoring, we accompany you with comprehensive service offerings – from initial start‑up through instrumentation maintenance to process optimization – as a true lifetime partner delivering improved outcomes.

For additional information, please contact your local Endress+Hauser representative.

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Personalized transaction space

Check prices and delivery times, save your favorite products, create quotes and place orders in just a few clicks and track deliveries at any time. With access to your complete order and quote history including all relevant documents you benefit from full transparency throughout the entire process.

Easy access to technical documentation

Select and download all technical documentation such as operating manuals, calibration certificates, approvals and CAD drawings conveniently bundled as a complete documentation package for your entire order or quote.

My Endress+Hauser – all in one place

My Endress+Hauser is your 24/7 connection to Endress+Hauser – in the office, in the field or on the go. It brings together transaction management, documentation and software downloads, knowledge base access, customer support, engineering tools and cloud‑based IIoT services helping you work easier, faster and more efficiently.

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Product information

Skin point thermometer
Tube skin thermometer TM691
Specifications
Measuring / Application task Thermometer
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Description

iTHERM SurfaceLine TM691 is a dedicated tube skin thermometer that measures tube wall temperature directly on the outside of process tubes, helping operators monitor thermal performance, detect overheating and protect tube integrity. Combining a standardized product structure, high configuration flexibility and specialist expertise, it enables reliable application-specific solutions for demanding thermal processes and harsh environments.

Field of application
  • Usage in the Oil & Gas, Chemical as well as Power & Energy industries
  • Typically for fired heaters, reformers, heat exchangers, boilers
  • Specifically designed for harsh environments with high temperatures, corrosion and vibration
Benefits
  • Increased plant and process safety: early detection of overheating and critical operating conditions of process pipes
  • Improved energy efficiency: Assessing and optimizing burner operation and heat distribution
  • Improved product quality: stabilized process conditions due to accurate temperature measurement
  • iTEMP temperature transmitter with all standard communication protocols and optional Bluetooth® connectivity
Downloads
Most downloaded
Technical Information (TI)
TI iTHERM SurfaceLine TM691 Surface thermometer
Metric/imperial TC tube skin thermometer for harsh environments such as fired heaters, reformers, heat exchangers, boilers
English version - 09/2026
Download
Innovation (IN)
Durable tube skin thermometer. iTHERM SurfaceLine TM691: Built for the toughest conditions.
English version - 09/2026
Download
Innovation (IN)
Robustes Oberflächenthermometer. iTHERM SurfaceLine TM691: Für härteste Einsatzbedingungen entwickelt.
German version - 10/2026
Download
The CAD Drawings will be available after the configuration.
All downloads
5 Downloads
Technical Information (TI)
TI iTHERM SurfaceLine TM691 Surface thermometer
Metric/imperial TC tube skin thermometer for harsh environments such as fired heaters, reformers, heat exchangers, boilers
English version - 09/2026
Download
Innovation (IN)
Durable tube skin thermometer. iTHERM SurfaceLine TM691: Built for the toughest conditions.
English version - 09/2026
Download
Innovation (IN)
Robustes Oberflächenthermometer. iTHERM SurfaceLine TM691: Für härteste Einsatzbedingungen entwickelt.
German version - 10/2026
Download
AI (Application note)
Rohrwandtemperaturmessung in einem Steamcracker-Ofen für die Ethylenproduktion
German version - 09/2026
Download
AI (Application note)
Tube skin temperature measurement in a steam-cracking furnace for ethylene production
English version - 09/2026
Download

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Skin point thermometer
Tube skin thermometer TM691
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Spare parts

further parts
further parts

iTEMP TMT31, Transmitter 4-20mA

further parts
further parts
Order code TMT31-
further parts
further parts

iTEMP TMT71, Transmitter 4-20mA

further parts
further parts
Order code TMT71-
further parts
further parts

iTEMP TMT72, Transmitter HART

further parts
further parts
Order code TMT72-
further parts
further parts

iTEMP TMT82, Transmitter HART

further parts
further parts
Order code TMT82-
Spare parts

Selection of compatible products

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