Endress+Hauser

Sensor class

Pt100 temperature sensors for industrial temperature measurement are mainly produced in two basic forms. The so called thin flim sensors and the round ceramic sensors.

The Pt100 is fitted into a measurement insert. The measurement accuracy is dependent on various factors:

Sensor measurement accuracy: Tolerance class, connection type (see the detailed description below)
Transmitter measurement accuracy (for specification see configurator)
Measurement point installation: Installation of the sensor and the electrical insulation of the sensor element. (Medium flow direction, minimum immersion length: 8x thermometer diameter, installation angle)

Pt100 temperature sensors

Pt100: thin film
Thin film sensors are a rectangular ceramic substrate (sizes from 2x2 to 2x10mm). Onto this basic form platinum it is added in a meandering formation. The two ends of the resistance are connected to the bonded connection wires. The complete sensor is then coated with a glass protection. These sensors can be used in a temperature range of -50 to 400 °C within the tolerance class B in accordance with the IEC 60751 or in a range of -50 to 250 °C in the tolerance class A. The tolerance class AA (formerly 1/3 DIN Class B) is also valid for the last mentioned range. Due to the sputter process these sensors can be industrially and economically produced in large numbers with extremely good results. Due to their construction these sensors are chemically resistant and relatively insensitive to mechanical vibrations.
Figure left: Pt100 in a stainless stell sheath (not bendable)
Figure right: The Pt100 as well as the internal cables are insulated using a highly compressed ceramic mass (magnesiumoxide powder MgO).

Advantages:
- Good long-term stability
- Short response-time
- Good vibration resistance

Ceramic Pt100
Wire wound Ceramic sensors consist of a ceramic body onto which a platinum wire is wound. The sensor is made mechanically solid by adding a second outer ceramic protection cover and is made chemically resistant by the addition of glass passivation. Due to this construction ceramic sensors can be applied in measurement ranges between -200 and 600 °C. Both tolerance class B and the higher tolerance class A are valid for the above mentioned temperature range. Due to the manufactureres details the limited AA (formerly 1/3 DIN B) tolerance class is only valid for the range -50 to 250 °C

Advantages:
- Good long-term stability
- Short response-time
- Adequate vibration resistance

Measurement accuracy sensor

Tolerance classes:

For Pt100 resistance thermometers two accuracy classifications are laid down in the IEC 60751:

Class A (at 0°C max. error ± 0.15°C equals 0.06 Ohm)
Class B (at 0°C max. error ± 0.3°C equals 0.12 Ohm)

Above these there are also higher accuracy classifications for special applications:

Class AA (formerly 1/3 B) (at 0°C max. error ± 0.1°C equals 0.04 Ohm)
Class 1/10 B (at 0°C max. error ± 0.03°C equals 0.012 Ohm)

Note
Each accuracy classe is only valid for certain temperature ranges (see below).
The classes A, AA (formerly 1/3 B) and 1/10 B should only be combined with a 4-wire connection.

Measurement accuracy for Pt 100 thin film TF:
(Measuring range -50 °C ... +400 °C)

Class	max. Tolerances (°C)	Validity
Class A	0.15 ± 0.002 · \|t\|1)	-50 °C to +250 °C
Class AA (formerly 1/3 B)	0.10 ± 0.0017 · \|t\|1)	0 °C to +150 °C
Class B	0.3 ± 0.005 · \|t\|1) -	-50 °C to +400 °C

1) |t| = absolute value of the temperature in C°

Measurement accuracy for Pt 100 wire wound WW:
(Measuring range -200 °C ... +600 °C)

Class	max. Tolerances (°C)	Validity
Class A	0.15 ± 0.002 · \|t\|1)	-200 °C to +600 °C
Class AA (formerly 1/3 B)	0.10 ± 0.0017 · \|t\|1)	0 °C to +250 °C
Class B	0.3 ± 0.005 · \|t\|1) -	-200 °C to +600 °C

1) |t| = absolute value of the temperature in C°

Connection modes

2-wire:
Electrical connection of the Pt100 resistance.
Features:
Additional measurement error due to temperature dependent resistance changes in the cabling.

3-wire:
Electrical connection of the Pt100 resistance.
Features:
Accurate measurement. In the main avoids additional measurement error due to temperature dependent resistance changes in the cabling.

4-wire:
Electrical connection of the Pt100 resistance.
Features:
Highly accurate. No additional measurement error due to temperature dependent resistance changes in the cabling.

Temperature inserts of Endress+Hauser by comparison

Sensor type	Construction	Application temperature range	Dual sensor available¹⁾	Best accuracy that is available for order by default		Long term stability	Best possible response time⁴⁾	Vibration resistance⁵⁾
RTD thin film (TF)		-50 °C to +400 °C (-58 °F to 752 °F)	yes, on request	Class AA (formerly 1/3 DIN B) according to IEC 60751²⁾ 0.1 + 0.0017 x \|t\|³⁾(valid from 0 °C to +100 °C, 32 °F to 212 °F))	++	+	+	+
RTD thin film (TF) Sensor on tip (on TMRxx and TTRxx)		-50 °C to +200 °C (-58 °F to 392 °F)	no	Class A according to IEC 60751²⁾0.15 °C + 0.002 x \|t\|³⁾ (valid from -50 °C to +200 °C, -58 °f to 392 °F))	+	+	++	+
RTD wire wound (WW - ceramics)		-200 °C to +600 °C (-328 °F to 1112 °F)	yes	Class AA (formerly 1/3 DIN B) according to IEC 60751²⁾ 0.1 + 0.0017 x \|t\|³⁾ (valid from 0 °C to +100 °C 32 °F to 212 °F)	++	+	+	0
Thermocouples (TC)		-200 °C to +1800 °C (-328 °F to 3272 °F) (depending on type)	yes	Example for type K: Class 1 according to EN 60584 1.5 °C (Valid from -40 °C to +375 °C, -40 °F to 707 °F) respectively. 0.004 x \|t\|³⁾ (valid from +375 °C to +1000 °C, 707 °F to 1832 °F)	0	0	++	++

1) 2 x PT100 respectively 2 x TC in one insert 2) even higher accuracy possible through sensor transmitter matching (calibration + use of the Callendar-Van-Dusen Coefficient) 3) \|t\| = absolute temperature in °C; for measurement errors in °F, calculate using equations above in °C, then multiply outcome by 1.8 4) depending on the construction 5) Caution on noticeable, heavy vibrations on the plant (e.g. paper machines) respectively strong flow peaks inside the process (e.g. steam pipelines) Please contact our Temperature Support Center for further information.
	++	particularly suitable
	+	well suitable
	0	suitable to only a limited extent