MINERAL INSULATED THERMOCOUPLES

The Mineral Insulated Metal Sheath Thermocouple (MIMS Thermocouple) has become the accepted norm within most industries. It features a variety of temperatures and corrosion resistant sheaths with long lasting operational usage. Thermocouples are used internationally as the cheapest and the most interchangeable temperature sensor available, with a universal connection system they can measure a wide range of temperatures. The Thermocouple is widely used in harsh environments as configurations allow for thick walls and explosion proof heads. Thermocouples main limitation is that the accuracy of up to 1°C can occur and certain temperatures over a period of time. History Shows that an Estonian physician by the name of Thomas Seebeck discovered (Accidentally), that the junction between two different metals generates a small voltage which can be converted into a temperature coefficient. The Thermocouple measures the difference in temperature between two points, the active end or hot junction and the sensor junction cold end junction. This cold end junction is maintained at a constant temperature and is referenced with an RTD or Thermistor allowing a known cold end junction for calibration. There are many different types of metals that can be used that when placed together that produce a stable constant predictable voltage source. A list of the most common voltage sources is listed below.
As the choice of Thermocouple is varied a few factors need to be considered before ordering:

Compatibility

If you are replacing an existing Thermocouple probe, take into account the space allowed for the probe, the holes that are already in place and the connection lead types. It is also useful to note the model and type of the measuring equipment used what type of Thermocouple or RTD the meter reads.

Temperature Range

As shown below in the table and in appendix A the temperature range is critical when choosing a Thermocouple probe, as an incorrect probe may not operate correctly in that temperature zone but still may show a temperature, this may prove dangerous given the situation. We recommend that you add 10% to the hottest or lowest temperature of the equipment under test as this will allow for a safety margin.

Sheathing Material

The outer sheath of the Thermocouple or RTD will provide protection against heat allowing a longer lasting probe, chemical attack and abrasion resistance for further reference refer to Sheathing materials chart.

 

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Overall Design

If planning a complete installation of temperature measuring equipment a range of factors needs to be taken into account:

• Environment the probe or measuring equipment is in wet, dry hot, cold and abrasive
• The length and position of the cable to connect equipment what machinery does it pass in getting to the probe. An option of solutions is available including Stainless Steel flex conduit metal ducting and wireless communication.
• Data Logging does the data need to be Stored and retrieved over a period of time forms of chart recorders data loggers USB memory are available.
• Temperature Control systems for machinery to activate or deactivate are available, the design must take into account set points ramping speeds and dwell times.

Thermocouple Extension Cable

A Thermocouple extension cable must reflect the environment it is placed. ie .The temperature range and machinery that it passes through to get to the measuring instrument is it hot, cold, or abrasive. Will the cable be driven on or suspended over a given distance? For a selection of Extension, cables refer to the cable section.

Hot end junction

There a three ways the hot end can be configured each of these produces a different result for different applications.

Insulated Junction

• The most common method of construction providing ungrounded probe elements. This style is Slower in response time but can be used when requiring a low EMF pick up. This is a general purpose application and provides the best compromise for reliability and overall performance.

Exposed Junctions

• This junction allows for the element wires to be directly exposed to the environment it is testing, this allows for faster response time but is extremely susceptible to corrosion and not recommended for higher temperature ranges.

Bonded junctions

• The bonded junction or grounded junction has the elements welded to the outer sheath. This provides a faster response time then insulated junctions but is not recommended for use in insulated control system networks.

Tip Design

There are many methods that these junctions can be applied to a tip of a Thermocouple to increase it’s reliability and response time.

Standard rounded tip

• This is the Standard Hot end to an insulated and Bonded junction Thermocouple using MgO powder insulation

Flat tip

• This is the Flat Hot end to and insulated and Bonded junction Thermocouple using MgO powder insulation, used when even end contact is required.

Swage tip

• This tip allows for greater response time when using larger size Mineral Insulated (M. I) Thermocouples while still providing the elements with protection.

Extended welded tip

• When requiring a permanent contact an extended weld can be added to the tip this allows the tip to be welded directly to the heat source for a faster response time.

Thermocouple styles available

ITEM	DESCRIPTION	BUY MOW	MORE INFORMATION
	THERMOCOUPLE STYLE  TA M.I. Thermocouple Solid Tails
	THERMOCOUPLE STYLE TB M.I. Thermocouple Flex Tails
	THERMOCOUPLE STYLE TC M.I. Thermocouple Flex or Solid Tails BSP/ NPT fittings
	THERMOCOUPLE STYLE TD M.I Thermocouple Flex Tails, Polarised Plug or Jack
	THERMOCOUPLE STYLE TE M.I Thermocouple Polarised Plug or Jack
	THERMOCOUPLE STYLE TF M.I thermocouple Stellite coated Polarised Plug or Jack
	THERMOCOUPLE STYLE TG M.I thermocouple Extension cable With S/S Armour
	THERMOCOUPLE STYLE TH M.I thermocouple Spring Loaded Terminal Block
	THERMOCOUPLE STYLE TI M.I thermocouple Spring Loaded Hex nipples
	THERMOCOUPLE STYLE TJ M.I thermocouple Surface Pad
	THERMOCOUPLE STYLE TK M.I thermocouple PROCESS FITTING
	THERMOCOUPLE STYLE TL M.I thermocouple Lug/washer all sizes
	THERMOCOUPLE STYLE TM M.I thermocouple bolt/threaded all sizes
	THERMOCOUPLE STYLE TN M.I thermocouple Magnetic surface probe
	THERMOCOUPLE STYLE TO Thermocouple Surface probe Straight
	THERMOCOUPLE STYLE TP Thermocouple Surface probe Right angles
	THERMOCOUPLE STYLE TQ M.I thermocouple Handheld probe Metal handle
	THERMOCOUPLE STYLE TR M.I thermocouple  MEAT STAB PROBE
	THERMOCOUPLE STYLE TS M.I thermocouple Small or Large head
	THERMOCOUPLE STYLE TT M.I thermocouple Small or Large head HEAVY DUTY THICK WALL
	THERMOCOUPLE STYLE TU M.I thermocouple Small or large head Holding tube Spring loaded
	THERMOCOUPLE STYLE TV M.I thermocouple PROCESS FITTING SPRING LOADED
	THERMOCOUPLE STYLE TW M.I thermocouple HOLDING TUBE PROCESS FITTINGS
	THERMOCOUPLE STYLE TX M.I thermocouple WITH FLANGE
	THERMOCOUPLE STYLE TY M.I thermocouple HOLDING TUBE & UNION
	THERMOCOUPLE STYLE TZ M.I thermocouple Small or large head Ceramic sheath
	THERMOCOUPLE STYLE TAA marshal tip thermocouple type k with holding handle
	THERMOCOUPLE STYLE TAB Thermocouple  Extension Cable Small Or Large Size Plugs or Jacks
	THERMOCOUPLE STYLE TAC Thermocouple Compensating Cable Junction all Options

 

 

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