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Thermocouples operate on the principle that when two dissimilar metals are joined at both ends and one of the ends is a different temperature, a measurable and repeatable EMF is produced. The preferred design for JMS thermocouples is mineral insulated sheath. The high purity, hard packed magnesium oxide provides excellent insulation of the positive and negative wire conductors in relation to each other and to the outer metal material.


The advantages of using RTD’s include accuracy, repeatability, and stability. Another advantage is that cold junction compensation is unnecessary. Copper wire is used for all connections. The signal level of an RTD is over ten times higher than that of a thermocouple which eliminates the need for high gain amplifiers. The signal is also less susceptible to noise than thermocouples. The accuracy of a 4 wire RTD is independent of the distance between the sensor and the readout instrument.

Thermowells, Protection Tubes, and Coatings

JMS manufactures all types of thermowells and protection tubes. For thermowell design and to receive instant drawings and quick quotes for your needs, register to use SwiftyCalc the free thermowell design software applying the ASME PTC 19.3 TW-2010 standard offered exclusively by JMS Southeast, Inc.

Plastics Industry Temperature Sensors

Bayonet style thermocouples are the most common in plastics processing. JMS has adapted this useful and safe design to other industrial sensors to utilize the best features of both. Our standard design and most commonly used is the Adjustable Bayonet attachment device developed by JMS in 1982. This design incorporates a Chrome-plated Brass cap with a stainless steel spring. The spring fits around the appropriately sized sensor and remains in position until such a time as the user adjusts it. This enables the same sensor to be used for many different applications in the same facility. It also makes for lower inventory levels which your accountant will love.

Sanitary Sensors, Sanitary Thermowells & Specialty Sensors

JMS has been recognized and authorized by 3-A Sanitary Standards to manufacture the highest quality RTDs, Thermocouples and Thermowells for the Pharmaceutical, Dairy, Food & Beverage Industries. In addition to these most common selections, JMS has 30 years of experience manufacturing customer sensors for sanitary applications.


The JMS SwiftyCalc quickly provides you with a thermowell design based upon your material requirements and process variables that you can count on to meet the ASME PTC 19.3-TW (2010) standard. SwiftyCalc is perfect for faster response time and increased reliability in your temperature measurement system.

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JMS Southeast Incorporated

We design and manufacture a complete line of high quality standard and customized temperature sensors including thermocouples, RTD's and Thermowells as well as a wide selection of temperature accessories.

  • Esablished: 1980

  • Headquarters: North Carolina, USA

  • Key Products: Temperature Sensors, Thermowells

  • Advantages: SwiftyCal, SwiftySensor

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