Endress+Hauser Omnigrad T TST310 Technical Information

Technical Information

Omnigrad T TST310

RTD thermometer
Can be screwed in or inserted
With fixed connected cable and anti-kink spring

Application

The resistance thermometer is specially suited to
temperature measurement in machinery, laboratory
equipment and plants in gaseous or liquid media like air,
water, oil and others.

Your benefits

• High flexibility through user-specific insertion lengths
and variable process connections

• Fast response time

• Single or double Pt100 sensor of accuracy class A, B,
or AA as per IEC 60751

• Types of protection for use in hazardous locations:
Intrinsic Safety (Ex ia)
Non-Sparking (Ex nA)

TI00085T/09/en
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TST310

Function and system design

Measuring principle These resistance thermometers use a Pt100 temperature sensor according to IEC 60751. This temperature

sensor is a temperature-sensitive platinum resistor with a resistance of 100 Ω at 0 °C (32 °F) and a temperature
coefficient α = 0.003851 °C

There are generally two different kinds of platinum resistance thermometers:

• Wire wound (WW): Here, a double coil of fine, high-purity platinum wire is located in a ceramic support.
This is then sealed top and bottom with a ceramic protective layer. Such resistance thermometers not only
facilitate very reproducible measurements but also offer good long-term stability of the resistance/
temperature characteristic within temperature ranges up to 600 °C (1112 °F). This type of sensor is relatively
large in size and it is comparatively sensitive to vibrations.

• Thin film platinum resistance thermometers (TF): A very thin, ultrapure platinum layer, approx. 1 μm
thick, is vaporized in a vacuum on a ceramic substrate and then structured photolithographically. The
platinum conductor paths formed in this way create the measuring resistance. Additional covering and
passivation layers are applied and reliably protect the thin platinum layer from contamination and oxidation
even at high temperatures.

The primary advantages of thin-film temperature sensors over wire wound versions are their smaller sizes and
better vibration resistance. A relatively low principle-based deviation of the resistance/temperature
characteristic from the standard characteristic of IEC 60751 can frequently be observed among TF sensors at
high temperatures. As a result, the tight limit values of tolerance category A as per IEC 60751 can only be
observed with TF sensors at temperatures up to approx. 300 °C (572 °F). For this reason, thin-film sensors are
generally only used for temperature measurements in ranges below 400 °C (932 °F).

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Measuring system

Example of an application

A Built-in RTD thermometer TST310
B Temperature transmitter iTEMP

resistance thermometer in a 2, 3, or 4-wire connection and converts them into an analog 4 to 20 mA measurement
signal.

C RIA16 field display unit

– The display unit measures the analog signal from the transmitter and shows this on the display. The LC display shows

the current measured value in digital form and as a bar graph indicating a limit value violation. The display unit is
looped into the 4 to 20 mA circuit and gets the required energy from there. More information on this can be found
in the Technical Information (see "Documentation").

D Active barrier RN221N

– The RN221N active barrier (24 V DC, 30 mA) has an galvanically isolated output for supplying voltage to loop

powered transmitters. The universal power supply works with an input supply voltage of 20 to 250 V DC/AC, 50/
60 Hz, which means that it can be used in all international power grids. More information on this can be found in
the Technical Information (see "Documentation").

®

DIN rail TMT12x. The two-wire transmitter detects the measurement signals of the

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TST310

Equipment architecture

Thermometer design, dimensions in mm (in)

1

Without process connection

2

With brazed process connection

3

With adjustable compression fitting

4

Cable sensor with ∅D = 3 mm (0.12 in) or 6 mm (0.24 in)

5

Transition sleeve

6

Anti-kink spring, 50 mm (1.97 in)

7

Connecting cable with variable cable diameter
∅K, see Table 'Connecting cable'

8

Process connection versions

L

Connecting cable length

NL

Insertion length

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The resistance thermometers of the Omnigrad T TST310 series are designed as cable sensors. The actual RTD
sensor element is fitted in the sensor tip and mechanically protected. In principle there are bendable and non­bendable versions of the cable sensor; for details, see → ä 9. The cable sensors generally consist of a stainless
steel tube in which the leads of the sensor element are routed and electrically insulated. Only the bendable
version uses mineral-insulated sheathed cables instead. The corresponding connecting cable is fastened to the
sensor using a transition sleeve.
The thermometer can be installed using either a movable compression fitting or a process connection firmly
brazed onto the thermometer. In addition, versions can be delivered for insertion without a special process
connection. For detailed process connection versions, see → ä 7.

Connection cable

Cable insulation; sheathing; leads Option Cable diameter ∅K in mm (in)

PVC; PVC; 4-wire A 4.8 (0.19)

PTFE; Silicone; 4-wire B 4.6 (0.18)

PTFE; PTFE; 4-wire C 4.5 (0.178)

PTFE; Silicone; 2x3-wire D 5.2 (0.2)

PTFE; Silicone; 4-wire E 4.0 (0.16)

Measurement range • -50 to +400 °C (-58 to +752 °F), bendable version, mineral-insulated sheathed cable

• -50 to +250 °C (-58 to +482 °F) non-bendable version, insulated sensor wires in the stainless steel tube

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Performance characteristics

Operating conditions Ambient temperature

The permitted ambient temperature is dependent on the material used for the electrical connecting cable and
the cable sheath insulation:

TST310

!

Material
Connection cable / sheath insulation

PVC / PVC 80 °C (176 °F)

PTFE / silicone 180 °C (356 °F)

PTFE / PTFE 200 °C (392 °F)

Process pressure

Max. process pressure (static) ≤ 75 bar (1088 psi).

Note!
For the maximum permitted process pressures for the respective process connections, refer to the Chapter
"Process connection" → ä 7.

Permitted flow velocity depending on the immersion length

The highest flow velocity tolerated by the thermometer diminishes with increasing immersion length exposed
to the stream of the fluid. In addition it is dependent on the diameter of the thermometer tip, on the kind of
measuring medium, on the process temperature and on the process pressure. The following figures exemplify
the maximum permitted flow velocities in water and superheated steam at a process pressure of 1 MPa (10 bar
= 145 PSI).

Max. temperature in °C (°F)

Permitted flow velocity

- Insert diameter 3 mm (0.12 in) ------------

- Insert diameter 6 mm (0.24 in) - - - - - -

A Medium water at T = 50 °C (122 °F) L Immersion length
B Medium superheated steam at T = 400 °C (752 °F) v Flow velocity

Shock and vibration resistance

3g / 10 to 500 Hz as per IEC 60751 (RTD-Thermometer)

Degree of protection

IP65

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