Multipoint Thermocouple (Multilevel)


MULTIPOINT THERMOCOUPLE (MULTILEVEL)

ARi can supply multiple element assemblies, also known as multipoint thermocouple, small enough to replace single point thermocouples. We also manufacture large multiple element assemblies which can replace expensive thermowells. It is now possible to insert a multilevel thermocouple assembly directly into a pressurized process chamber with minimum flow restriction and a response time that is measured in seconds. This fast response time will allow detection of abnormal process temperature conditions before damage can occur.

Multiple level temperature sensors (Multipoint Thermocouple) have junctions space to provide continuous temperature profiles. The sensing end of the thermocouple assembly may be formed or bent around offsets and the assembly can withstand the following external pressures:0.125″ — 3000psig and 0.500″ — 4000psig.

  • Assembly sheath may be welded or brazed in place or installed with a single compression fitting.
  • Individual thermocouple circuits may either be fully insulated from each other or available with junctions grounded to inner sheaths for faster response time.
  • Assemblies can be installed into existing thermowells or into fast response protection tubes.
  • A time constant of 3 seconds at 3 meters/second water velocity can be attained with a 0.125″ diameter assembly.
  • Multiple element thermocouple assemblies are used to obtain continuous temperature data at pre-selected points. Previous approaches required the installation of several thermocouples into large thermowells.
  • Up to 18 thermocouples can be provided in a single 0.125″ outer sheath.

Available in the following calibration types:

Calibration Type

Temp Range °F

Temp Range °C
J

-300 to 1000

-184 to 540
K

32 to 1800

240 to 980
E

-400 to 1800

-240 to 980
 
 
Typical Multilevel Designs
 Multipoint Thermocouple (T-50656) Multipoint Thermocouple (T-50657) Multipoint Thermocouple (T-50780) Multipoint Thermocouple (T-50809)
Multipoint Thermocouple Application Notes:
  • To replace single point sensors in existing thermowells.
  • Installed in a low clearance location.
  • Fast response unit protection tube.
  • Brazed into process line.
Other terminations are available.  Please contact ARi for more information.

MATERIAL SPECIFICATION

 

MULTI-LEVEL THERMOCOUPLE

Style T-50656 T-50657 & T-50780 T-50809
Outer Diameter 0.125″ ± 0.002″ 0.500″ ± 0.005″ 0.125″ ± 0.002″ 0.500″ ± 0.005″ 0.125″ ± 0.002″ 0.500″ ± 0.005″
Transition Section ½” NPT Nipple x 4″ Long  ½” NPT Nipple x 4″ Long ½” NPT Nipple x 4″ Long ½” NPT Nipple x 4″ Long ½” NPT Nipple x 4″ Long ½” NPT Nipple x 4″ Long
Length Range (L) 6″ to 240″ ± 1″ Tolerance 12″ to 240″ ± 1″ Tolerance 6″ to 240″ ± 1″ Tolerance 12″ to 240″ ± 1″ Tolerance 6″ to 240″ ± 1″ Tolerance 12″ to 240″ ± 1″ Tolerance
Max Pressure at 100 °F 3000 psig 4000 psig 3000 psig 4000 psig 3000 psig 4000 psig
Time Constant at 3 MPS Water Velocity (grounded junction) 3 sec. 10 sec. 3 sec.   10 sec.  3 sec. 10 sec. 
Weight per Unit Length 0.3 lb/ft 0.45 lb/ft 0.3 lb/ft 0.45 lb/ft 0.3 lb/ft 0.45 lb/ft
Minimum Bend Radius for (L) Section to Avoid Permanent Set 0.5″ 12″  0.5″  12″  0.5″ 12″ 
Number of Points Available 2 to 4 2 to 7 2 to 4 2 to 6 2 to 3 2 to 3

Notes:

  1. Junctions equally spaced or provided with location per customer requirements.
  2. Assemblies are available in intermediate sizes.  Please consult ARi.

 

Calibration And Sheath Materials

Calibration Type Outer Sheath Materials
Wire Type Temp Range °F Temp Range °C Sheath Type ARi Symbol Maximum Temp °F
 J -300 to 1000 -184 to 540 304 ST/ST A 1600
K 32 to 1800 240 to 980 Inconel 600* B 1800
E -400 to 1800 -240 to 980 316 ST/ST C 1600
347 ST/ST F 1600

  Multipoint Thermocouple Part Number