What does the name Pt100 stand for?

Pt100 is a resistance temperature detector, made of material Platinum (= Pt_) and its resistance value at 0 °C temperature is 100 ohm (=_100). Hence the name is Pt100. More details on page How do Pt100 sensors work?

What means 2-, 3- and 4-wire connection?

A resistance temperature detector (=RTD) can be connected with 2, 3 or 4 wires. The 2-wire connection needs only 2 wires, but then the measuring electronics is measuring also wire resistance, which is not desirable. Using extra wires for compensating the cable resistance gives more precisely the desired resistance of the RTD itself. The 4-wire connection is the most accurate one.

Why is 4-wire connection recommended with Pt100 Class A (acc. to IEC 60751)?

Only 4-wire connection is completely compensating the wire resistance effect of the whole cable circuit. With 2- or 3-wire connections there might be possibility to manually program the measured cable resistance as a transmitter parameter to correct the final readout. But even in these cases the parameter is correct only at the ambient temperature of the moment of measuring the cable. The measurement circuit loses its accuracy if the ambient temperature changes. The 4-wire connection compensates also ambient temperature variations. The Class A Pt100 RTDs are meant for accurate temperature measurement, that’s why the wire connection should always be implemented with 4 wires. More details on page How do Pt100 sensors work?

What is MI-cable?

Mineral Insulated (= MI) cables are bendable metal tubes with wires and mineral insulation inside. Used with RTD sensors the MI cable has copper wires and with TC sensor the wire materials are according to the TC type. The mineral insulation in form of oxide powder is closely packed around the wires inside the tube, which can be made of stainless steel or e.g. Inconel. These materials and this construction give a unique temperature range to be applied in various measuring solutions.

What is Seebeck effect?

When two wires of different metals or metal alloys (thermo wires) are joined together in one end (hot junction), a thermocouple is formed. If there is a temperature difference between the hot junction and the open ends, a thermal electromotive force (a thermal voltage) is created in the thermocouple. This is also called the Seebeck effect. More details on page How do TC sensors work?

What is CJC?

A thermocouple measurement always needs information from joined wire end (hot junction) and open wire end (cold junction). The cold junction is also called reference point. Variations of reference point temperature are compensated with CJC measuring (Cold Junction Compensation). Temperature transmitters CJC measuring can be an internal function or a measuring resistor integrated in connectors. If the reference point is far away from the transmitter, a separate temperature measuring of that point has to be implemented and wired to transmitter as compensation signal. More details on page How do TC sensors work?

What is Compensating cable and Extension cable?

Compensating cable is a thermocouple measuring circuit cable, which is identified by the letter C (e.g. for type K cable KC). Wires of the compensating cable have the same electrical features, but not the same materials, as the thermo wires of the TC sensor. Compensating cable is a more cost effective solution than extension cable, but the maximum ambient temperature allowed is lower, approximately 100…200 °C depending on the insulation material.

Extension cable is a thermocouple cable which is identified by the letter X (e.g. for type K cable KX). Wires of the extension cable are of exactly the same materials as the thermo wires of the TC sensor. These cables can achieve even the same ambient temperatures as the thermocouple can.

What are the Pt100 accuracy classes?

Accuracy classes and tolerances defined by IEC 60751:2008 are:

  • Class AA ± (0,1+0,0017 * t), ±0,1 °C (0 °C), ±0,27 °C (100 °C), defined on range -50…+250 °C (wire wound resistor), 0…+150 °C (thin film resistor)
  • Class A ± (0,15+0,002 * t), ±0,15 °C (0 °C), ±0,35 °C (100 °C), defined on range -100…+450 °C (wire wound resistor), -30…+300 °C (thin film resistor)
  • Class B ± (0,3+0,005 * t), ±0,3 °C (0 °C), ±0,8 °C (100 °C), defined on range -196…+600 °C (wire wound resistor), -50…+500 °C (thin film resistor)
  • Class C ± (0,6+0,01 * t), not commonly used for industrial measuring circuits.

SKS Sensors® Pt100 resistors are wire wound resistors of Class A as standard.

What is 1/3 DIN and 1/10 DIN?

Standard DIN EN 60751:2009 (based on IEC 60751:2008) defines Pt100 resistance accuracy Classes AA, A, B and C and corresponding tolerances. Before standard update the most accurate class was A and all definitions more accurate were non-standardized, divided Class B values.

  • 1/3 DIN is a divided value, based on Class B, not applicable over the whole measuring range. This divided accuracy is only defined at the point: 0 °C = ± 0,3/3 °C= ± 0,1 °C. Class B 1/3 DIN is not a standardized class.
  • 1/10 DIN is a divided value, based on Class B, not applicable over the whole measuring range. This divided accuracy is only defined at the point: 0 °C = ± 0,3/10 °C = ± 0,03 °C. Class B 1/10 DIN is not a standardized class.

The standardized Class AA since standard update has made the divided values 1/3 DIN dispensable.

How to define a SKS Sensors® temperature sensor type?

SKS Sensors® temperature sensor's type designation is an informative line of characters, which is defined by a specific code key. Code keys for each sensor type are presented within product data, please find the information of all individual sensor types 1...22 under title Products > Temperature sensors.

Build your type designation code with the Product selection tool
You can create the right code for your application step-by-step, choosing one feature at a time and writing the basic dimension data to the relevant filter fields of the tool. The resulting code is a link to accurate product data and you are also provided with a quick link to a quotation request cart. Check out the tool under title Products > Product selection tool.

Old types before 1.12.2008
SKS Sensors® temperature sensor types were shortened and made more informative 1.12.2008. Type change shortened and unified the product designations, however leaving old product numbers active. In our sales system we can still find the old product designation, but it will be changed to a new one every time we send an order confirmation. New types have been used since 1.12.2008.

If You need any assistance in converting an old sensor type to a new one, please don't hesitate to contact Your SKS Sensors® dealer.

What is calibration?

  • Definition of calibration: temperature sensors deviation in individual points of measuring range is defined by comparing the readout of the sensor to be calibrated to another reference sensor, which readout accuracy is known.
  • Objective of calibration: to define the deviation between a measured value and a corresponding reference value.

Why to calibrate?

Through calibration You can achieve many more advantages besides measuring accuracy:

  • traceability for temperature measuring results
  • certainty for temperature measuring results
  • optimizing production process quality, consistency and efficiency
  • energy savings due process control driven by accurate measurements
  • reduced pollution due process control driven by accurate measurements
  • savings in material costs
  • minimizing risk of unexpected repairs and changes of process machinery and sensors.

Details of calibrating services offered by SKS Automaatio on page Services.

Are there CE markings in temperature sensors?

The CE marking symbolizes conformity of the product with one or more applicable European product directives. The product shall be provided with an EU Declaration of Conformity document, which defines the directive(s) and the applicable standards the product conforms to.

The product shall not bear a CE mark, if no European directive applies to it.

Regarding the SKS Sensors® temperature measuring sensors this means briefly: the safe area sensors do bear CE markings since 22.7.2017, while the ATEX approved sensors for explosive atmospheres do already have a CE mark.

Reasons for this for each potentially applicable directive individually are explained on page Are there CE markings in temperature sensors?

What is trace heating / sensor?

Trace heating is a term usually used for keeping pipelines and attached devices unfrozen. The important function of trace heating is maintaining stable temperature and flow rate of the materials flowing through the pipeline. The most common implementation of trace heating is electrical, which offers good adjustability. However, for accurate process control and adjustment also precise temperature data is needed. For these applications we have designed our high quality trace heating sensors, which already have been available for years, also for Ex applications.


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