Rdf T-77 - Print Version

DATA SHEET T-77

RdF Corporation offers a complete line of Mineral-Insulated Thermocouples for industrial applications.

Available in either single or dual junction assemblies,
the Series 77 Thermocouples feature special accuracy limits,
strong and flexible stranded 20 AWG wire leads and
all-welded construction.

TYPE A - Straight Probe Assembly Adjustable fittings are available with 1/2", 1/4", or 1/8" NPT mounting. Seal at lead exit temperature rated to 500°F.

TYPE B - Probe with Hex Fitting This probe is for direct immersion. Use spring loaded (77D) with thermowells. Lead exit temperature 500°F.

TYPE C - Probe with Quick Disconnect Plug and Jack Available in 1/8" and 1/4" diameter with connector. Rated to 475°F

77
A/B/C

SERIES RIGID THERMOCOUPLE WITH 1/2 X 1/2 HEX FITTING FOR DIRECT IMMERSION
STYLE (SEE ABOVE)

SHEATH DIAMETER (1/16" STEPS)

2
3
4

1/8" (“A” Requires Transition - 1.75 x 0.25)
3/16" (Dual “A” Requires Transition - 1.75 x 0.25, Style A or B only)
1/4"

SHEATH MATERIAL

S
I
O

316 SS
Inconel 600
Other (A or C only, No Transition)

ANSI TYPE THERMOCOUPLE (special limits of error)

Single
J
T
K
E

Dual
JJ
TT
KK
EE

Iron Constantan
Copper Constantan
Chromel Alumel
Chromel Constantan

PROBE LENGTH IN INCHES

   TYPE OF JUNCTION
     G   Grounded Junction
     U   Ungrounded Junction
     X   Exposed Junction

CONNECTION HEAD (see table below)

LEAD LENGTH (Specify in inches)
(4" leads with connection head - standard)


	77B

–


	4

–


	S

–


	K

–


	8

–


	U

–


	B

–


	4

–

Typical Write-Up for 77B

CONNECTION HEADS


	NEMA 4 w/gasket	Conduit	Max. Temp

A	Small cast aluminum head	1/2 NPT	125°C

B	High temp. small cast aluminum head	1/2 NPT	260°C

C	Cast Iron head	3/4 NPT	260°C

D	For no connection head specify “D”

E	Large cast aluminum head	3/4 NPT	260°C

F	Economy conduit body	1/2 NPT	125°C

G	Explosion proof small cast aluminum head	1/2 NPT	125°C

H	High temp. expl. proof small cast alum. head	1/2 NPT	260°C

I	Hinged plastic	3/4 NPT	125°C

J	Hinged cast aluminum	3/4 NPT	125°C

K	Din B cast aluminum	1/2 NPT	100°C

S	Other (please specify when ordering)

T	Transmitter, specify or supply w/head

	* up to 4 terminal standard, styles E & C can have 6 terminals

TYPE 77D

Thermowell not included—order separately;
see data sheet T-WELLS

77D

SPRING LOADED MGO INSULATED SHEATHED THERMOCOUPLE FOR MOUTNNG IN THERMOWELL
Note: Thermowell not included, see Data Sheet T-WELLS.

4 SHEATH DIAMETER (1/4" DIA ONLY)

SHEATH MATERIAL

S
I

316 SS
Inconel 600

ANSI TYPE THERMOCOUPLE (special limits of error)

Single
J
T
K
E

Dual
JJ
TT
KK
EE

Iron Constantan
Copper Constantan
Chromel Alumel
Chromel Constantan

STEM (“A”) LENGTH OF PROBE IN INCHES (same dimension as thermowell “A”)

   TYPE OF JUNCTION
     G   Grounded Junction
     U   Ungrounded Junction

CONNECTION HEAD (see table below)

PROBE LAG HARDWARE
1/2" NPT Fittings, Stainless Steel

A

BX

EX

FX

Hex Nipple is 3/4" long standard.
Specify as “A”

Specify as “BX”, where x=3", 6", 9", or 12" Standard (Straight Nipple)

Specify with aluminum union as “EX”
(Hex-Nipple/Union/Nipple)
where x = mated lengths of 3"
and continuing in 1" increments

Same as EX (Stainless Steel Union)

LEAD LENGTH (Specify in inches)
(4" leads with connection head standard)


	77D

–


	4

–


	S

–


	K

–


	8

–


	U

–


	B

–


	B3

–


	4

–

Typical write-up for 77D

Connection Head	Lag Hardware


	• ANSI types J, T, K, E; Traceable to NIST • Special Limits of Error • Single or dual junctions • Stainless steel fittings • Inconel or stainless steel sheaths • TIG welded construction	• Strong and flexible stranded 20 AWG • leads, fiberglass insulated and • jacketed cable • Stainless steel or aluminum lag unions • Cast aluminum heads with up to • 8 terminal posts

GROUNDED – The thermocouple wires are welded directly to the sheath end closure and are completely protected. Recommended for fast responding direct immersion probes. Time constant <2.5 sec. in water flowing at 3 ft/sec. Isolated instrumentation required.

UNGROUNDED – The thermocouple junction is electrically insulated from the external sheath with compacted magnesium oxide powder. Recommended in all applications to minimize instrumentation ground loops. Time constant <5 sec. in water flowing at 3 ft/sec.

EXPOSED – The thermocouple junction extends beyond the sheath providing fast response. For low pressure gasses to reduced maximum temperatures.

THERMOCOUPLE DATA - THERMOCOUPLE TYPES

Iron-Constantan (ANSI Symbol J)
The Iron-Constantan “J” curve thermocouple with a positive iron wire and a negative constantan wire is recommended for reducing atmospheres. The operating range for this alloy combination is 1600°F for the largest wires sizes. Smaller size wires should operate in correspondingly lower temperatures, Limit exposed junctions to 900°F continuous use.

Copper-Constantan (ANSI Symbol T)
The Copper-Constantan “T” curve thermocouple with a positive copper wire and a negative constantan wire is recommended for use in mildly oxidizing and reducing atmospheres up to 750°F.

They are suitable for applications where moisture is present. This alloy is recommended for low temperature work since the homogeneity of the component wires can be maintained better than other base metal wires. Therefore, errors due to inhomogeneity of wires in zones of temperature gradient are greatly reduced. Limit exposed junctions to 500°F long term use.

Chromel-Alumel (ANSI Symbol K)
The Chrome-Alumel “K” curve thermocouple with a positive chromel wire and a negative alumel wire is recommended for use in clean oxidizing atmospheres. The operating range for this alloy is

2300°F for the largest wire sizes. Smaller wire sizes should operate at correspondingly lower temperatures. The only suitable choice for exposed junctions from 1000°F to 1800°F.

Chromel-Constantan (ANSI Symbol E)
The Chromel-Constantan thermocouple may be used for temperatures up to 1600°F in a vacuum, inert, mildly oxidizing or reducing atmosphere. At sub-zero temperatures, the thermocouple is not subject to corrosion. This thermocouple has the highest emf output of any standard metallic thermocouple. Limit exposed junctions to 1000°F continuous use.

THERMOCOUPLE MATERIAL

RANGE AND LIMITS OF ERROR

ANSI
Type

Positive

Negative
(red color)

Positive
(color code)

Temperature Range, °F
(1/8"dia./1/4"dia.)

Standard
(whichever is greater)

Special
(whichever is greater)

Iron
(magnetic)

Constantan

White

32 to 970/1330

±4°F or ±0.75%

±2°F or ±0.4%

Chromel

Alumel
(magnetic)

Yellow

–320 to 32
32 to 1900/2100

±4°F or ±2%
±4°F or ±0.75%

±2°F or ±0.4%

Copper
(copper color)

Constantan

Blue

–320 to 32
32 to 600/700

±1.8°F or ±1.5%
±1.8°F or ±0.75%

±0.9°F or ±0.4%

Chromel

Constantan
(silver color)

Purple

–320 to 32
32 to 1200/1510

±3°F or ±1%
±3°F or ±0.5%

±1.8°F or ±0.4%



	*RdF Corporation • 23 Elm Ave., Hudson, NH 03051* 800.445.8367 • 603.882.5195 • fax 603.882.6925 • www.rdfcorp.com