Usage limitations and accuracies of platinum resistance thermometers (DIN EN 60751:2009) in industrial applications
WIKA data sheet IN 00.17
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WIKA data sheet IN 00.17 ∙ 10/2010General information
T emperature is a measurement for the thermal state of a material - so a measurement of the average kinetic energy of its molecules. A clo thermal contact between two bodies is needed in order that the bodies adopt the same tempera-ture (temperature equalisation). The body to be measured should be coupled as cloly as possible to the temperature nsor system.
The most established temperature measurement methods are bad on material or body properties that change depend-ing on the temperature. One of the most-ud methods is the measurement with a resistance thermometer.
乘>政治协商制度This document outlines the recurrent concepts and technologies that apply to all resistance thermometers produced by WIKA.
麻辣鱼Standard version
If there are no additional specifications or customer require -ments, we will recommend this lection, or we will lect this option when offering or producing the thermometer.
Sensor technology
The electrical resistance of a resistance thermometer‘s
nsor changes with respect to the temperature. If the resist-ance increas when temperature is raid, we refer to it as PTC (P ositive T emperature C oefficient).
Pt100 or Pt1000 measuring resistors are normally ud for industrial applications. The exact characteristics of the measuring resistors, and the thermometers bad on them, are defined in DIN EN 60751 (2009-05). The most important characteristics are described in this document.
Basic values for resistance at 0 °C
Bold: standard version
Measuring resistor designs
Tho measuring resistors ud in thermometers can be wire-wound resistors (W = Wire-Wound) or thin-film resistors (F = Thin-F ilm).
刘备借荆州歇后语Fig. left: Thin-film resistor Fig. center: Glass resistor Fig. right: Ceramic resistor
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Page 2 of 8WIKA data sheet IN 00.17 ∙ 10/2010
Thin-film resistor
Glass resistor
Ceramic resistor
Thin film resistors (F) (standard design)
For thin-film resistors, a very thin platinum film is applied to a ceramic carrier plate. Following this connecting wires are attached. Finally, the platinum film and the connecting wire connection are aled against external effects by a layer of glass. Thin-film resistors are characterid by their very small size and high vibration resistance.
The thin film resistor is characterid by ■T emperature range: -50 ... +500 °C * ■High vibration resistance ■Very small size
■Good price/performance ratio
Thin-film resistors are the standard design unless the
temperature range or an explicit customer request exclude them.
Wire-wound resistors (W)
For the designs, a thin platinum wire is encad within a round protective body. This design has proven itlf over the decades and is accepted throughout the world.
T wo subtypes are available that differ in the choice of insulat -ing material.
Glass resistor
The bifilar wire of the glass resistor is fud within a glass body.
The glass resistor is characterid by ■T emperature range: -200 ... +400 °C * ■High vibration resist
ance
Ceramic resistor
The platinum wire of the ceramic resistor is spiral-wound and located in a round cavity in the protective body.The ceramic resistor is characterid by ■T emperature range: -200 ... +600 °C * ■Limited vibration resistance
* The specifications apply to Cass B, e table on Page 4.
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WIKA data sheet IN 00.17 ∙ 10/2010Sensor connection methods
2-wire connection
The lead resistance to the nsor is recorded as an error in the measurement. For this reason, this connection type is not advisable when using Pt100 measuring resistors for tolerance class A and AA, since the electrical resistance of the connecting cables and their own temperature
dependency are fully included in the measurement result and thus falsify it.
Applications
■Connecting cables up to 250 mm
■Standard when using Pt1000 measuring resistors
3-wire connection (standard design)
The influence of the lead resistance is compensated as far as possible. The maximum length of the connecting cable depends on the conductor cross-ction and the compensa-tion options of the evaluation electronics (transmitter, display, controller or process control system). Applications
■Connecting cables up to approx. 30 m
4-wire connection
The influence of the connecting cable on the result of
measurement is completely eliminated since any possible asymmetries in the connecting cable‘s lead resistances are also compensated.
The maximum length of the connecting cable depends on the conductor cross ction and on the compensation options of the electronic evaluation (transmitter, display, controller or distributed control system). A 4-wire connection can also be ud as 2-wire or 3-wire connection by disconnecting the unnecessary conductors.
Applications
■Laboratory technology ■Calibration technology ■T olerance Class A or AA
■Connecting cables up to 1000 m
Dual nsors
In the standard design a single nsor is fitted.
The combination of black and yellow is rerved for an
optional cond measuring resistor. For certain combinations (e.g. small diameter) dual nsors are not possible for techni-cal reasons.
Relation between temperature and resistance
For each temperature there is an exact resistance value. This clear relation can be described with mathematical formulas.
For the temperature range -200 ... 0 °C the following applies, irrespective of the resistor design:
R t = R0 [1 + At + Bt² + C (t - 100 °C) •t³ ]
For the temperature range 0 ... 600 °C the following applies: R t = R0 [1 + At + Bt² ]Legend:
t=T emperature in °C
R t=Resistance in Ohms at the measured temperature R0=Resistance in Ohms at t = 0 °C (e.g. 100
Ohm)
The following constants apply for the calculation:
A=3.9083 • 10-3 (°C -1 )
B=-5.7750 • 10-7 (°C -2 )
C=-4.1830 • 10-12 (°C -4 )
Usage limitation and tolerance class
Both measuring resistor versions (wire-wound/thin-film) differ
in the possible accuracies at the operating temperatures.
1) | t | is the value of the temperature in °C without consideration of the sign
Bold: Standard version
Page 4 of 8WIKA data sheet IN 00.17 ∙ 10/2010
Determined vibration resistance Peak value in [g]*
关于普通话的手抄报Vibration resistance in accor-dance with DIN EN 60751 in [g]*
* = 9.81 m/s²
Bold: standard version
A c c e l e r a t i o n [g ]
Time
Peak-to-peak value
Peak value
一年级手抄报Vibration resistance of resistance thermometers
In accordance with DIN EN 60751, the design of a resis-tance thermometer can be influenced by vibration-induced accelerations that can be up to 30 m/s² and occur in a frequency range from 10 to 500 Hz. The standard refers to the peak-to-peak value (e DIN EN 60751 Edition 1996).
In order to guarantee the comparability of pressure and temperature measuring instruments, WIKA tests all designs under the same test conditions. Since every other standard (e.g. IEC 60068 Environmental tests) refers to the peak value of vibrations, WIKA also tests the thermometers in this way.The specifications determined this way can be converted using a factor of 2 into specifications conforming to DIN EN 60751.
If the frequency is known and constant, the acceleration, speed and deflection can be calculated from each other.The frequency of the vibration is ud to calculate the …angular frequency“:
ω = 2 π ƒ
If the peak value of the vibration, A, is given, the following applies to the maximum speed V max :
V max =
A
ω
This can be ud to determine the deflection from the refer -ence line x max :
硬盘怎样分区
x max =
V max
ω
The space required for the vibration, i.e. the difference
between the deflections, can be shown as the peak-to-peak value of the deflection:
x s2s = 2 x max
Legend:
ω=Angular frequency in 1/c
A
=Peak value, i.e. maximum value of the acceleration, in m/c²
v max
=Maximum value of the speed during vibration, in m/c
x max =Maximum deflection from the rest position in one direc -tion, in m
x S2S =Peak-to-peak value of the deflection, i.e. difference bet -ween the two extreme values of the deflection, in m
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WIKA data sheet IN 00.17 ∙ 10/2010
