
Technical Information
TI093T/02/en
No. 71108018
RTD Thermometer
omnigrad TST90
Process thermometer - Building automation
Ø 6 mm M.I. replaceable inset
Straight and Reduced Tip - Matched pairs
Description
TST90 RTD thermometer assembly
includes a replaceable single Pt100 inset
in mineral insulated cable, a terminal
head and a thermowell.
The inset is equipped with special
matched Pt100 for thermal energy
measurement.
The terminal head can be selected from a
wide choice of standard items (see the
Order key or the TA20 Technical
Information for more details).
The thermowell can be delivered with a
reduced tip for fast response time.
TST90 is always delivered in matched
pairs.
Application
Typical application can be found in heat
exchangers for inlet and outlet differential
temperature measurement.
The thermal energy can be calculated
knowing ΔT between inlet and outlet,
flowrate and other parameters.

Technical data
omnigrad TST90
Mineral insulated
replaceable inset
Version: TET90
Sensing element: Platinum resistance, 1 Pt100 Ω at 0°C, thinfilm type
Tolerances: matched pairs, ±0.05 K (0÷120°C) or ±0.1 K (-40÷0°)
Wiring: 2 or 4 wire connections
Insulation resistance:
≥ 100 MΩ , test voltage 250 V at ambient temperature
Electrical connections: terminal block
Stem: mineral insulated cable (MgO)
Sheath: AISI 316L/W.1.4404
Standard diameter: 6 mm straight tip type or 3x50 reduced tip type
Operating temperature: -50 ... +200 °C
IL
Response time values: according to IEC751 in moving water at 0.4 m/s
= 24 s ; T90 =72 s (straight tip)
T
50
T50 = 7.5 s; T90 = 20.5 s (reduced tip)
Internal resistance: for 2 wire electrical connection compensation
0.06 Ω/m for each single conductor (straight tip)
0.12 Ω/m for each single conductor (reduced tip)
Replacement: inset length IL is calculated as follows
d 6
TET inset
sensing
length
=
25 m m
IL = L + 155 mm
Protecting tube Version: TA10 thermowell
Standard diameter: 9x7 mm
Reduced tip: see drawing next page
Standard material: AISI 316Ti/W.1.4404
Connection to head: M24 x 1.5
Process connection: G 1/2" - M
Max. operat. condition: 50 bar @ 20°C; 1 bar @ 400°C
Terminal head Version, protection class and electrical connection: refer to order key
2 Endress+Hauser

omnigrad TST90
• For inset replacement see
Technical data
• Accuracy statement is referred to
the replaceable inset only as
defined by IEC 751 without any
protecting thermowell which may
introduce thermal drift due to
process connection heat
dissipation in conjuction to short
immersion lengths.
For a correct temperature
measurement the thermowell
immersion length must be 20 times
its diameter. Shorter immersion
lengths can be supplied but the
thermometer requires an external
(process connection, neck and
connection head) thermal
insulation.
Order key
TST90- RTD THERMOMETER - Building automation
Ø 6 mm M.I. replaceable inset - Straight and Reduced Tip - Matched pairs
Material of the thermowell
1 AISI 316TI-W1.4571
9 Material to specification
Insertion Length L (75-3700mm)
U 100 mm insertion length
D 160 mm insertion length
F 250 mm insertion length
K 400 mm insertion length
X mm insertion length to spec.
Y mm special insertion length
Sensor material
1 Thermowell AISI 316TI-W1.4571
9 Thermowell material to spec.
Shape of the tip
S Straight tip, standard response
T Reduced tip, fast response
Type of terminal
3 Terminal block
9 To specification
Class and type of inset
1S2 1 Pt100, 2 wire, cal. 0,05K (0 - 120 °C)
1S4 1 Pt100, 4 wire, cal. 0,05K (0 - 120 °C)
1U4 1 Pt100, 4 wire, cal. 0,1K (-40 - 0 °C)
9Y9 To specification
Ter mi nal he ad
A TA20A:M24 bottom, Pg16 Grey, IP67
B TA20B:M24 bottom, Pg16 Grey, IP67
D TA20D:M24 bottom, Pg16 Grey, IP66
Y To specification
TST90- Complete Order Code
Endress+Hauser 3

S upplementary
Documentation
• Technical Information TET90 Ø6 mm M.I. Inset (TI 225T/02/en)
• Technical Information TA20 terminal heads (TI 072T/02/en)
TI093T/02/en/04.01
FM+SGML 6.
0 No.: 71108018
Endress+Hauser
Gmbh+Co.
Instruments International
P.O. Box 2222
D-79574 Weil am Rhein
Germany
Tel. (07621) 975-02
Tx 773926
Fax (07621) 975 345
http://www.endress.com
info@ii.endress.com