Specifications

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Siemens FI 01 · 2015 US Edition
Temperature Measurement
SITRANS TS500
Technical description
2
Measuring technology: Mounting depth
Measuring insert
Immersion depth/contact with media
Ambient conditions (temperature/climate/insulation) and the de-
sign of the thermowell, process connection and piping result in
so-called "heat transmission errors".
To prevent such an error, the submersion depth and diameter of
the thermowell tip will be defined. The temperature-sensitive
length (TSL) of the thermowell must also be taken into account.
The following rule of thumb can be used:
• Water
Submersion depth  TSL + 5 x Ø of thermowell
•Air
Submersion depth  TSL + 10 ... 15 x Ø of thermowell
• Recommendations
- Select largest possible submersion depth
- Select measuring location with higher flow velocity
- Thermal insulation for outer thermometer components
- Smallest possible surface for outer components
- Insertion in pipe bends
- Direct measurements without additional thermowell if no suit-
able solution can be found using other measures.
Measuring technology: Connection types
In the case of resistance thermometers, the type of sensor con-
nection directly affects the level of accuracy:
Two-wire system
The resistance of sensor lines are included in the measurement
result as an error. Adjustments are recommended in this case.
Pt100 Two-wire system
Three-wire system
Line resistance is not included in the measurement result. Re-
quirements: all terminal and line resistances (corrosion) are at
the same level, and terminals are at the same temperature level.
Pt100 Three-wire system
Four-wire system
Line resistance is not included in the measurement result. This
type of connection is the most secure and most accurate.
Pt100 Four-wire system
Siemens measuring inserts can be used to implement all types
of connections for 1 x Pt100 devices. In the case of 2 x Pt100 ver-
sions, two- and three-wire systems are also possible. For mea-
surement-related reasons, we always recommend a 1 x four-wire
or 2 x 3-wire connection.
Type Temperature-sensi-
tive length (TSL
[mm (inch)]
Non-bendable length
[mm (inch)]
Basic 50 (1.97) 30 (1.82)
Increased vibration
resistance
50 (1.97) 30 (1.82)
Expanded measur-
ing range
50 (1.97) 60 (2.36)
Thermocouple 20 (0.79) 5 (0.20)
Pt100
Pt100
Pt100
© Siemens AG 2015